Tekmar Boiler Control 275 User manual

1 of 48 © 2012 D275 - 01/12
Boiler Control 275
D275
01/12
Replaces:03/09
Installation & Operation Manual
Multi-Staging
The Boiler Control 275 is designed to stage up to four condensing or non-condensing, modulating or on-off boilers using
P.I.D. staging to accurately maintain temperature. The control supports hybrid boiler plants that contain both condensing
and non-condensing boiler groups. Water temperature is controlled by outdoor reset for space heating applications or a
fixed setpoint for Domestic Hot Water (DHW) tank heating or industrial process heating applications. The control will also
accept an analog signal from an Energy Management System (EMS) to control the water temperature. Boiler equal run-time
rotation, pump exercising and stand-by system pump operation increase boiler plant reliability. The control is tekmarNet®
communication compatible allowing for internet connectivity using an optional Gateway 483.
tN4 Compatible
BTC I Compatible
24 Hour, 5-11, 5-2, 7 Day Schedule
Flow or Combustion Air Proof
Four Modulating or On/Off Boilers
•
•
•
•
•
Equal Run Time Rotation
Primary Pump Sequencing
DHW Operation
Optional DHW Sensor
Setpoint Operation
•
•
•
•
•
Additional functions include:
Setback
Boiler Control 275
One tN4, Four Modulating Boiler & DHW / Setpoint
Menu Item
Test
Boiler Demand
DHW / Setpoint Demand
Proof Demand
EMS Input Signal
Priority Override
Power 115 V ±10% 60 Hz 7 VA, 1150 VA max.
Relays 230 V (ac) 5 A 1/3 hp
Demands 20 to 260 V (ac) 2 VA
Designed and assembled in Canada by
tekmar Control Systems Ltd
tektra 1020-01
Meets Class B:
Canadian ICES
FCC Part 15
For maximum heat,
press and hold Test
button for 3 seconds.
not testing
testing
testing paused
off
red
red
BTC I
Off
EMS Rotate Fixed Last
Pump Sequencer
Exercise
Off
Demands
Date Code
H2048B
Signal wiring must be rated at least 300 V.
DHW
29
/SetpCom
30
Dem Pr.
31
Dem
2
–
5
–
Mod1
1
+Mod2
3
+
–+Mod3
4
+Mod4
6
+
BRet/
7
Com
8
tN4
12
Boil
9
Out
10
Com
11
Prim
P1 L N
26
Power
28271413
Do not apply power
24
DHW
/ P2
23 251615 1817 2019 2221
Fixed Lead
First On / Last Off
First On / First Off
Relay
1Relay 2Relay 3Relay 4C.A. / Alert Boiler Demand
Sup DHW
Zone Load Shedding
Input
Universal
Sensor
Included
Input
Universal
Sensor
Included
tN4
Boiler
Bus
Input
Outdoor Sensor
Included
OR
0-10 or 2-10 V (dc)
from EMS
Output
Up to 4
Modulating
Boilers
Input
115 V (ac)
Power Supply
Input
Flow OR
C.A. Proof
Output
Up to 4
Boiler Pumps
OR Boiler Enable
Output
DHW Pump
OR
Primary Pump
Output
Combustion
Air Damper
OR Alert
OR
OR
Output
Primary
Pump
Input
DHW OR
Setpoint
Demand
Signal
Input
Boiler
Demand
Signal

© 2012 D275 - 01/12 2 of 48
How to Use the Data Brochure
Table of Contents
This brochure is organized into three main sections.
They are: 1) Sequence of Operation,
2) Installation,
3) Control Settings and
4) Testing and Troubleshooting.
The Control Settings section of this brochure describes
the various items that are adjusted and displayed by the
control. The control functions of each adjustable item are
described in the Sequence of Operation.
User Interface...............................................................2
Display and Symbol Description...................................3
Access Level.................................................................4
Sequence of Operation.................................................4
Section A: Boiler Demand........................................4
Section B: Outdoor Reset......................................... 4
Section C: Boiler Operation......................................6
Section D: Modulating Boilers..................................8
Section E: On / Off Boilers ..................................... 10
Section F: OEM Boilers Equipped With A BTC I.... 10
Section G: Fixed Lead and Fixed Last ................... 10
Section H: Condensing and Non-Condensing Boiler
Groups ................................................................... 10
Section I: Domestic Hot Water Operation .............. 11
Section J: Setpoint Operation ................................ 14
Section K: Energy Management System (EMS) .... 16
Section L: Pump Operation.................................... 17
Section M: Combustion Air and Alert Settings ....... 18
Section N: Setting the Schedule ............................ 19
Section O: Time Clock ...........................................20
Section P: Boost.....................................................20
Section Q: Exercising.............................................20
Section R: tekmarNet®4 Communication................20
Section S: Scene Operation................................... 21
Installation ..................................................................22
Control Settings .........................................................28
Cleaning the Control ..............................................28
DIP Switch Settings................................................28
VIEW Menu............................................................30
ADJUST Menu .......................................................32
TIME Menu.............................................................39
SCHEDULE Menu..................................................40
MISC Menu ............................................................43
Testing the Control......................................................44
Error Messages .......................................................... 45
Technical Data............................................................48
Limited Warranty ....................................................... 48
The control uses a Liquid Crystal Display (LCD) as the
method of supplying information. You use the LCD in
order to setup and monitor the operation of your system.
The control has four push buttons (Menu, Item, ▲, ▼) for
selecting and adjusting settings. As you program your
control, record your settings in the ADJUST menu table,
which is found in the second half of this brochure.
Menu
All of the items displayed by the control are organized
into five menus (View, Adjust, Time, Schedule, and Misc).
These menus are listed on the top left hand side of the
display (Menu Field). To select a menu, use the Menu
button. By pressing and releasing the Menu button, the
display sequences between the five menus. Once a menu
is selected, there will be a group of items that can be viewed
within the menu.
Item
The abbreviated name of the selected item will be displayed
in the item field of the display. To view the next available
item, press and release the Item button. Once you have
reached the last available item in a menu, pressing and
releasing the Item button will return the display to the first
item in the selected menu.
The items can be quickly scrolled through by holding the
Item button and then pressing the ▼ button. To rapidly
scroll through the items in the reverse order, hold the
Item button and press the ▲ button.
Adjust
To make an adjustment to a setting in the control, begin by
selecting the ADJUST, TIME, SCHEDULE or MISC menu
using the Menu button. Then select the desired item using
the Item button. Finally, use the ▲, and / or ▼ button to make
the adjustment.
Additional information can be gained by observing the
Status field of the LCD. The status field will indicate
which of the control’s outputs are currently active. Most
symbols in the status field are only visible when the
VIEW menu is selected.
User Interface

3 of 48 © 2012 D275 - 01/12
Display
PRIMARY PUMP
Displays when primary pump 1 or
primary pump 2 is in operation
BOILER
Displays which modulating output is
operating
LOCK
Displays when adjusting Access level if
Switch is set to lock.
WARNING
Displays when an error exists.
COMMUNICATION BUS
Displays when tN4 thermostats are
connected.
DHW PUMP
Displays when the DHW Pump is
operating
°F, °C, MINUTES, AM, %, PM,
HOURS
Units of measurement.
BOILER PUMP
Displays when the boiler pump 1, 2, 3,
or 4 are operating
COMBUSTION AIR DAMPER
Displays when the combustion air
damper relay is closed
SCHEDULE MASTER
Displays when the 275 is a schedule
master
WARM WEATHER SHUT DOWN
Displays when the control is in warm
weather shut down
MINIMUM & MAXIMUM
Displays when the boil target or the boil
supply is at a minimum or maximum
Schd Wake
UnOcc Sleep
Away
Schd, Wake, UnOcc, Sleep, Away
Displays the current event of a
schedule or scene
POINTER
Displays the control operation as
indicated by the text
Symbol Description
Item Field
Displays the current
item selected
Buttons
Selects Menus, Items
and adjusts settings
Number Field
Displays the current value
of the selected item
Status Field
Displays the current
status of the control’s
inputs, outputs and
operation
Menu Field
Displays the
current menu
Menu Item

© 2012 D275 - 01/12 4 of 48
Once the control receives a boiler demand it calculates a
target water temperature based on the characterized heating
curve to provide outdoor reset for space heating. The control
can receive a boiler demand three different ways:
1. By applying 20-260 V (ac) to the boiler demand
terminals (27 & 28) when the DIP switch is set to
Demands.
2. From an Energy Management System (EMS) by
applying a 0-10 or 2-10 V (dc) signal to terminals 2 &
3 when the DIP switch is set to EMS.
3. From a tN4 device. This requires a tN4 thermostat to
be wired to terminals 1 & 2 so that the call for heat
can go over the communication bus.
2827
Boiler
Demand
20-260 V (ac)
Demand
OR OR
0-10 or
2-10 V (dc)
from EMS tN4
Demand
23
–+
OutCom
21
–
tN4 Com
Boiler Demand Section A
Outdoor Reset Section B
Sequence of Operation
In a heating system, the rate of heat supplied to the building
must equal the rate at which heat is lost. If the two rates are
not equal, the building will either cool off or over heat.
The rate of building heat loss depends mostly on the outdoor
temperature. Outdoor Reset allows a hot water heating
system to increase the water temperature, adding heat to
the building, as the outdoor temperature drops. The rate
at which the water temperature is changed as a function
of outdoor temperature is defined by the characterized
heating curve.
Characterized Heating Curve
A characterized heating curve determines the amount the
target water temperature is raised for every 1°drop in outdoor
air temperature.
The characterized heating curve takes into account the
type of terminal unit that the system is using. Since different
types of heating terminal units transfer heat to a space using
different proportions of radiation, convection and conduction,
the supply water temperature must be controlled differently.
The control uses the terminal unit setting to vary the supply
water temperature to suit the terminal unit being used. This
improves the control of the air temperature in the building.
Boiler Characterized Heating Curve
Terminal
Unit
Boiler
Design
Boiler
Indoor
Outdoor
Design
Decreasing Outdoor Temperatures
Increasing Water Temperatures
The access level restricts the number of Menus, Items,
and Adjustments that can be accessed by the user. The
Access Level setting is found in the Miscellaneous (MISC)
Menu. Select the appropriate access level for the people
who work with the control on a regular basis. There are
three Access Level Settings:
User (USER): Select this access level for building
supervisors and other non-technical staff to prevent
unauthorized access to installer and advanced level
settings.
•
Installer (INST): Select this access level to limit some of
the settings available to the installer. This is the factory
default access level.
Advanced (ADV): Select this access level to have complete
access to all of the control settings. In the display menu
tables, the appropriate access level needed to view each
item is shown in the Access column.
Note: the Lock / Unlock switch on the front of the control
must be set to unlock to change the access level.
•
•
Access Level
In order for the control to have a target water temperature there must be a demand. There are three different demands the
control can have: boiler demand, DHW demand, and setpoint demand.

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Terminal Unit Setting in Adjust Menu
Select the appropriate terminal unit in the adjust menu.
This will change the shape of the characterized heating
curve to better match the heat transfer properties of that
specific terminal unit.
Hydronic Radiant Floor (HRF1)
A heavy or high mass, hydronic radiant floor system. This
type of a hydronic radiant floor is embedded in either a thick
concrete or gypsum pour. This heating system has a large
thermal mass and is slow acting.
Hydronic Radiant Floor (HRF2)
A light or low mass, hydronic radiant floor system. Most
commonly, this type of radiant heating system is attached to
the bottom of a wood sub floor, suspended in the joist space,
or sandwiched between the subfloor and the surface. This
type of radiant system has a relatively low thermal mass
and responds faster than a high mass system.
Fancoil (COIL)
A fancoil terminal unit or air handling unit (AHU) consisting
of a hydronic heating coil and either a fan or blower. Air is
forced across the coil at a constant velocity by the fan or
blower and is then delivered into the building space.
Fin–tube Convector (CONV)
A convector terminal unit is made up of a heating element
with fins on it. This type of terminal unit relies on the natural
convection of air across the heating element to deliver
heated air into the space. The amount of natural convection
is dependant on the supply water temperature to the heating
element and the room air temperature.
Radiator (RAD)
A radiator terminal unit has a large heated surface that is
exposed to the room. A radiator provides heat to the room
through radiant heat transfer and natural convection.
Baseboard (BASE)
A baseboard terminal unit is similar to a radiator, but has
a low profile and is installed at the base of the wall. The
proportion of heat transferred by radiation from a baseboard
is greater than that from a fin-tube convector.
Boiler Terminal Unit Defaults
When a terminal unit is selected for boiler zones, the
control loads default values for the boiler design, boiler
maximum supply, and boiler minimum supply temperatures.
The factory defaults can be changed to better match the
installed system. Locate the Terminal Unit setting in the
Adjust menu.
Terminal Unit BOIL DSGN BOIL MAX BOIL MIN
High Mass Radiant 120°F (49°C) 140°F (60°C) OFF
Low Mass Radiant 140°F (60°C) 160°F (71°C) OFF
Fancoil 190°F (88°C) 210°F (99°C) 140°F (60°C)
Fin-Tube Convector 180°F (82°C) 200°F (93°C) 140°F (60°C)
Radiator 160°F (71°C) 180°F (82°C) 140°F (60°C)
Baseboard 150°F (76°C) 170°F (77°C) 140°F (60°C)
Room Setting in Adjust Menu
The Room setting is the desired room air temperature,
according to the outdoor reset heating curve. The Room
setting parallel shifts the heating curve up or down to
change the target water temperature. Adjust the Room
setting to increase or decrease the amount of heat available
to the building. Once the heating curve has been set up
properly, the Room setting is the only setting that needs to
be adjusted. The default Room setting is 70°F (21°C), and
it can be adjusted for both the occupied and unoccupied
periods.

© 2012 D275 - 01/12 6 of 48
Outdoor Design Setting in Adjust Menu
The outdoor design temperature is typically the coldest
outdoor air temperature of the year. This temperature is
used when doing the heat loss calculations for the building
and is used to size the heating system equipment. If a cold
outdoor design temperature is selected, the supply water
temperature rises gradually as the outdoor temperature
drops. If a warm outdoor design temperature is selected,
the supply water temperature rises rapidly as the outdoor
temperature drops.
Boiler Indoor Setting in Adjust Menu
The boiler indoor design temperature is the indoor
temperature the heating designer chose while calculating the
heat loss for the boiler water heated zones. This temperature
is typically 70°F (21.0°C). This setting establishes the
beginning of the boiler characterized heating curve.
Boiler Design Setting in Adjust Menu
The boiler design supply temperature is the boiler water
temperature required to heat the zones at the outdoor design
temperature, or on the typical coldest day of the year.
(Default automatically changes based on terminal unit
setting)
Warm Weather Shut Down (WWSD) Setting in Adjust
Menu
Warm Weather Shut Down disables the heating system when
the outdoor air temperature rises above this programmable
setting. When the control enters into WWSD, the LCD will
indicate this in the status field. WWSD is only available
when the DIP switch = Demands. The boilers will operate
when a Domestic Hot Water (DHW) demand or a Setpoint
Demand is present.
Boiler Operation Section C
The 275 is able to operate up to four modulating or on-off
boilers as a heat source. For proper operation of the boilers,
the 275 must be the only control that determines when a
boiler is to fire.
*Important note: The boiler operator, or aquastat, remains
in the burner circuit and acts as a secondary upper limit
on the boiler temperature. The boiler aquastat temperature
setting must be adjusted above the 275’s boiler maximum
setting in order to prevent short cycling of the burner.
Boiler Target Temperature
The boiler target temperature is determined by connected tN4
devices or by a Boiler, DHW or Setpoint demand received
by the control. An Energy Management System (EMS) can
also give a boiler target. The tN4 devices determine the
highest water temperature required and then request this
temperature on the tN4 boiler bus. The temperature request
creates a Boiler Demand and this is indicated on the display.
A DHW demand and a Setpoint demand have temperature
settings to which the boilers are operated to meet and are
able to override the tN4 bus temperature if required. The
control displays the temperature that it is currently trying to
maintain as the boiler supply temperature in the View menu.
If the control does not presently have a requirement for heat,
it does not show a boiler target temperature. Instead, “– – –”
is displayed in the LCD.
Boiler Minimum Setting in Adjust Menu
The boiler minimum is the lowest temperature that the
control is allowed to use as a boiler target temperature.
During mild conditions, if the control calculates a boiler
target temperature that is below the boiler minimum setting,
the boiler target temperature is adjusted to at least the
boiler minimum setting. The MIN segment is displayed in
the LCD while viewing the boiler supply or target and when
the boiler target is boiler minimum and the boiler supply is
less than boiler minimum plus 5°F (2.5°C). Set the Boiler
Minimum setting to the boiler manufacturer’s recommended
temperature.
Boil MIN
MIN segment on
Boil MIN + 5°F (2.5°C)
Boiler Differential
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Boiler Maximum Setting in Adjust Menu
The boiler maximum is the highest temperature that the
control is allowed to use as a boiler target temperature.
The MAX segment is displayed in the LCD while viewing
the boiler supply or target and when the boiler target is
boiler maximum and the boiler supply is greater than boiler
maximum minus 5°F (2.5°C). Set the boiler maximum
setting below the boiler operator or aquastat temperature.
At no time does the control operate the boiler above 248°F
(120°C).
Boil MAX
Boil MAX – 5°F (2.5°C)
Boiler Differential
MAX
segment
on
MAX
segment
on
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7 of 48 © 2012 D275 - 01/12
Stage Delay Setting in Adjust Menu
The Stage Delay is the minimum time delay between the
firing of each stage. After this delay has expired the control
can fire the next stage if it is required. This setting can be
adjusted manually or set to an automatic setting. When the
automatic setting is used, the control determines the best
stage delay based on the operation of the system.
Boiler Relay Setting in Adjust Menu (per boiler)
The 275 provides a dry contact for either burner ignition or
boiler pump. Selection is made through the Boiler RELAY
setting in the adjust menu. Select ‘burner’ for boilers that
require a boiler enable signal as well as a modulating signal
in order to operate. Select pump to operate a boiler pump
with post purge capabilities.
Boiler Mass Setting in Adjust Menu (per boiler)
Match the boiler mass setting with the thermal mass
characteristics of each boiler. The modulation of the boiler
can become unstable if the incorrect Boiler Mass setting is
chosen. A key sign of unstable boiler modulation is that the
flame will continue to increase and then decrease in short
periods of time. By choosing a lower boiler mass setting,
the boiler response will become more stable.
LO
The LO setting is selected if the boiler that is used has
a low thermal mass. This means that the boiler has very
small water content and has very little metal in the heat
exchanger. A boiler that has a low thermal mass comes
up to temperature quite rapidly when fired. This is typical
of many copper fin-tube boilers.
The Lo mass setting provides a fast response to the heating
system.
MED
The MED setting is selected if the boiler that is used has
a medium thermal mass. This means that the boiler either
has a large water content and a low metal content or a
low water content and a high metal content. This is typical
of many modern residential cast iron boilers or steel tube
boilers.
The Med mass setting provides a moderate response to
the heating system.
HI
The HI setting is selected if the boiler that is used has a
high thermal mass. This means that the boiler has both
large water content and a large metal content. A boiler that
has a high thermal mass is relatively slow in coming up to
temperature. This is typical of many commercial cast iron
and steel tube boilers.
The Hi mass setting provides a slow response to the
heating system.
Boiler Differential Setting in Adjust Menu
A modulating boiler must be operated with a differential
while operating at Minimum Modulation. When the boiler
is modulating above Minimum Modulation, the differential
does not apply. Instead, the modulation output signal is
determined using Proportional, Integral, and Derivative (PID)
logic in order to satisfy the boiler target temperature.
The boiler differential can be fixed or automatically
determined by the control. The Auto Differential setting
balances the amount of temperature swing in the boiler
supply temperature with boiler on times, off times, and
cycle times. This reduces potential short cycling during
light load conditions.
Manual Differential
Differential = 10°F (6°C) Target + 1/2 Differential
Target – 1/2 Differential
Target
165°F (74°C)
160°F (71°C)
155°F (68°C)
Boiler
On Boiler On
Automatic Differential
Off
Differential
Time
Heating Load
On
Rotation
The Rotate feature changes the firing order of the boilers
whenever one boiler accumulates 48 hours more run time
than any other boiler. Rotation will be forced if any boiler
accumulates 60 hours more run time. After each rotation,
the boiler with the least running hours is the first to fire and
the boiler with the most running hours is the last to fire.
This function ensures that all of the boilers receive equal
amounts of use. When the Rotate / Off DIP switch is set
to the Off position, the firing sequence always begins with
lowest boiler to the highest boiler.
720 hours
1 2
672 hours 720 hours
2 1
672 hours
To reset the rotation sequence (without regard to historical
running hours), toggle the Rotation DIP Switch Off for 3
seconds and on again. Note that the running hours (see
Run Time) in the View menu also need to be reset if you
want the rotation sequence and running hours display to
be synchronized.
Boiler Run Time in View Menu
The running time of each boiler is logged in the view menu.
To reset the running time, select the appropriate Boiler Run
Time in the View menu and press and hold the Up and
Down buttons together until CLR is displayed.

© 2012 D275 - 01/12 8 of 48
Modulating Boilers Section D
The 275 can operate up to four modulating boilers. The
control also provides dry contacts for either burner ignition
or boiler pump. Selection is made through Boiler Relay
setting in the Adjust menu.
Once a boiler is required to operate, the control outputs
an analog signal corresponding to the Start Modulation
setting and then turns on the boiler relay. Once the Fire
Delay time has elapsed, the modulating output is adjusted
to the Minimum Modulation setting. The control then holds
the modulating output at Minimum Modulation until the
Minimum Modulation Delay time has elapsed. Proportional,
Integral and Derivative (PID) logic is used in order to satisfy
the boiler target temperature.
Modulation Mode Setting in Adjust Menu
The control includes a Modulation Mode setting that
selects either Sequential or Parallel Modulation. Sequential
modulation should be used on boilers that are more efficient
when operating at high fire. Parallel modulation should be
used on boilers that are more efficient when operating at
low fire.
Sequential Modulation
In sequential modulation, the first boiler is turned on and
is modulated to satisfy light loads. Once the first boiler
does not have enough capacity to satisfy the load, the first
boiler reduces its modulation to provide a smooth transition
when the second boiler fires at low fire. The first boiler
then modulates up to maximum modulation as the load
increases. Only then is the second boiler able to increase
its output as the load continues to increase. When the third
boiler is required, the second boiler reduces its modulation
to allow the third boiler to operate at low fire. As the load
continues to increase, the second boiler is modulated to
its maximum and then the third boiler is modulated. The
operation is reversed when shutting off the boilers.
100% 60% Off Off
Parallel Modulation
In parallel modulation, the first boiler turns on at low fire
and begins to increase its modulation. Once the first boiler’s
output is greater than the combined output of the first and
second boiler’s low fire, the first boiler is modulated down
to low fire and the second boiler is fired at low fire. The
two boilers now modulate together. Once the two boiler’s
combined output is greater than the combined output of
all three boilers operating at low fire, the first and second
boilers are modulated down to low fire, and all three boilers
are operated at low fire. The boilers are then modulated
as the load increases. The operation is reversed when
shutting off the boilers.
40% 40% 40% 40%
Boiler Start Modulation Setting in Adjust Menu
(per boiler)
The Start Modulation setting is the lowest modulation
output required to obtain proper ignition. Whenever boiler
operation is required, the control outputs an analog signal
corresponding to the Start Modulation setting and closes
the boiler contact to turn on the burner. After the Fire Delay
has elapsed and the burner is ignited, the control modulates
the firing rate between the Minimum Modulation setting and
the Maximum Modulation setting.
Boiler Fire Delay Setting in Adjust Menu
(per boiler)
The Boiler Fire Delay sets the time it takes for the boiler to
generate flame from the time the boiler turns on.
Boiler Contact Closed
Time
Fire Delay
Burner On
Boiler Motor Speed Setting in Adjust Menu
(per boiler)
The Motor Speed is the amount of time the boiler requires
to go from 0% modulation to 100% modulation.
Gas valve actuating motors have a design time from
fully closed to fully opened which can be found in the
manufacturer’s manual. The Motor Speed should be set
to this time.
The Motor Speed setting for a Variable Frequency Drive
(VFD) is the amount of time required to go from a stopped
position to 100% fan speed. Since a VFD has a very quick
response rate, it may be necessary to increase the Motor
Speed setting in order to increase the stability of the boiler
modulation.
OR
Boiler % Modulation in View Menu
View the current % modulation of each boiler in the View
menu.

9 of 48 © 2012 D275 - 01/12
Boiler Minimum Modulation Setting in Adjust Menu
(per boiler)
The Minimum Modulation setting is the lowest modulation
output to obtain low fire. The Minimum Modulation setting
is typically based on the turndown ratio of the boiler. The
control adjusts the modulating output signal from Minimum
Modulation to 0% after the burner turns off and boiler
operation is not required.
To calculate the Minimum Modulation, use the following
formula:
For 0 to 10 V (dc):
Minimum
Modulation =
0V(dc) – Boiler’s Minimum
Input Signal x100%
0 – 10 V (dc)
Example:
A boiler requires a 1.8 V (dc) signal to fire the boiler at
low fire. The boiler can be modulated to 10 V (dc) where it
reaches high fire. This means the boiler’s input signal range
is 1.8 to 10 V (dc). The 275 control has an output signal
range of 0 to 10 V (dc).
To make the two signal ranges the same, the Minimum
Modulation required is:
Minimum Modulation = (0 – 1.8) ÷ (0 – 10) x 100% = 18%
Control’s
Output
Signal
Range
Boiler’s
Input
Signal
Range
100%
10 V (dc) 10 V (dc)
0 V (dc)
88%
Boiler’s
Minimum
Input
Signal
Minimum
Modulation
0%
1.8 V (dc)
18%
Minimum Modulation Delay Setting in Adjust Menu
(per boiler)
The Minimum Modulation Delay is the time that the boiler
burner must hold the modulation of the boiler at a minimum
before allowing it to modulate any further.
Boiler Maximum Modulation Setting in Adjust Menu
(per boiler)
The Maximum Modulation defines the maximum output
signal from the control to the boiler burner. It is based on
a percentage of the control’s output signal range. The
maximum modulation setting for boilers with power burners
is typically set to 100%.
For boilers with electronic operators, the boiler’s input signal
range may not match the output signal range of the 275
control. The Maximum Modulation setting limits the control
output range in order to match the boiler’s input range.
To calculate the Maximum Modulation, use the following
formula:
For 0 to 10 V (dc):
Maximum
Modulation =
0V(dc) – Boiler’s Maximum
Input Signal x100%
0 – 10 V (dc)
Example:
A boiler’s input signal range is 0 to 9 V (dc). The 275
control has an output signal range of 0 to 10 V (dc). To
make the two signal ranges the same, the Maximum
Modulation required is:
Maximum Modulation = (0 – 9) ÷ (0 – 10) x 100% = 90%
Control’s
Output
Signal
Range
Boiler’s
Input
Signal
Range
100%
10 V (dc)
9 V (dc)
0 V (dc)0 V (dc)
88%
Boiler’s
Maximum
Input
Signal
Maximum
Modulation
0%
Minimum and Maximum Boiler Outputs (MBH)
Setting in Adjust Menu
(per boiler)
In order to accommodate different boiler capacities in the
same system, a minimum and maximum boiler output
for each boiler can be set. This allows the control to
properly operate the boilers using either sequential or
parallel modulation. Each boiler typically has a rating plate
that specifies the minimum and maximum output. This
information is also available in the boiler manual.
The minimum and maximum boiler output is expressed
in MBH. 1 MBH = 1,000 BTU / hour. The range is from 1
MBH to 1,999 MBH.
For example, if a boiler has a maximum output of 100,000
BTU / hr and a minimum output of 20,000 BTU / hr (turn
down ratio of 5):
Maximum Boiler Output = 100,000 = 100 MBH
1,000
Minimum Boiler Output = 20,000 = 20 MBH
1,000

© 2012 D275 - 01/12 10 of 48
On / Off Boilers Section E
OEM Boilers Equipped With A BTC I Control Section F
The 275 can sequence up to four boilers equipped with an
integral BTC I control. Boilers that include the BTC I control
may have multi-stage or modulating burners. Each boiler
is connected to the 275 using two wires connected to the
Mod + and - wiring terminals for each boiler stage. The 275
also allows combinations of multi-stage boilers together with
modulating boilers. In total, the 275 is able to control up to
16 stages. For information on BTC I equipped boilers and
how to installed with the 275, please see tekmar Service
Bulletin SB 055.
The 275 can operate up to four modulating or on/off boilers
in any combination. Each boiler stage has a Boiler Mode
setting in the the Adjust menu that allows the selection of
either modulating (Mod) or on/off (OnOF). By selecting a
boiler stage to on/off, the 275 then uses sequential boiler
staging, the stage relay is set to operate a burner, and
settings related to modulation are removed from the boiler
settings.
Fixed Lead and Fixed Last Section G
Condensing and Non-Condensing Boiler Groups Section H
Fixed Last
In some applications, it may be desirable to have the last
boiler fire last at all times while the firing sequence of
the remaining boilers is changed using Equal Run Time
Rotation. This configuration is typical of installations where
the boiler plant includes higher efficient boilers and a single
lesser efficient boiler. The lesser efficient boiler is only
desired to be operated when all other boilers in the plant are
on and the load cannot be satisfied. This rotation option is
selected by setting the Fixed Last / Off DIP switch to Fixed
Last. With a fixed last rotation, the last boiler is the last to
stage on and the first to stage off. The Fixed Last is always
applied to the boiler 4 output.
Fixed Lead & First On / First Off
In some applications, it may be desirable to have the first
boiler fire first at all times while the firing sequence of
the remaining boilers is changed using Equal Run Time
Rotation. This rotation option is selected by setting the Fixed
Lead / Off DIP switch to the Fixed Lead position. The Fixed
Lead is always applied to the boiler 1 output.
When using the Fixed Lead rotation option, a selection must
be made between First On / Last Off and First On / First
Off using the DIP switch.
When First On / First Off is selected, the lead boiler is always
staged on first and staged off first. This configuration is
typical of installations where the boiler plant includes similar
boilers but the first boiler is required to be the first to fire in
order to establish sufficient draft for venting.
Fixed Lead & First On / Last Off
When First On / Last Off is selected, the lead boiler is
always staged on first and staged off last. This configuration
is typical of installations where the boiler plant includes a
single higher efficient boiler with lesser efficient boilers.
The lead boiler is the high efficiency boiler, therefore it the
last boiler to be sequenced off.
Operating a boiler plant that contains both condensing
(high initial cost) and non-condensing (lower intial cost)
boilers allows the boiler plant to achieve nearly the same
operating efficiencies as operating all condensing boilers
but at a much lower installed cost to the building owner.
High system efficiency can be acheived as long as the
condensing boilers are the first to operate in the firing
sequence. During mild weather, the lead condensing boilers
operate at lower boiler temperatures and achieve their peak
boiler effiencies while the non-condensing boilers are rarely
operated. During very cold weather, the boiler target is often
above the boiler’s condensation point and the condensing
and non-condensing boilers operate together at roughly
the same efficiency level.
The 275 supports the operation of condensing and non-
condensing boilers as separate groups through either the
Fixed Lead or Fixed Last options. When a condensing
boiler is operating, it is desirable to operate the boilers
without a boiler minimum temperature being applied to the
boiler target. This allows the condensing boiler to operate
at its maximum efficiency. When a non-condensing boiler
is operating, a boiler minimum temperature should be
applied to the boiler target to prevent damage to the non-
condensing boiler heat exchanger from sustained flue gas
condensation.
To operate one to three condensing boilers as the lead
boiler group, and operate a single non-condensing boiler
as the lag boiler, set the Fixed Last / Off DIP switch to the
Fixed Last position and select the Condensing Lead (COND
LEAD) setting to on. The boilers within the condensing lead
group can be operated using Equal Run Time Rotation to
balance running hours.
To operate a single condensing boiler as the lead boiler,
and operate one to three non-condensing boilers as the lag
group, set the Fixed Lead / Off DIP switch to the Fixed Lead
position and select the Condensing Lead (COND LEAD)
setting to on. The boilers within the non-condensing lag
group can be operated using Equal Run Time Rotation to
balance running hours.
In the event that Fixed Lead or Fixed Last is selected and
all boiler are non-condensing, select the Condensing Lead
(COND LEAD) setting to off.

11 of 48 © 2012 D275 - 01/12
Domestic Hot Water Operation Section I
DHW operation is only available when the Pump Sequencer
DIP Switch is set to Off.
DHW Demand
DHW Demands come from one of three sources: an external
aquastat, a DHW tank sensor, or a tN4 Setpoint Control.
Once the control detects a DHW Demand, the DHW
Demand segment is displayed in the LCD. If an External
Powered DHW Demand is applied while the DHW sensor
is enabled in the 275, an error message is generated and
both demands are ignored.
A DHW demand from a tN4 Setpoint Control can coexist with
another DHW demand without generating an error message.
The 275 will then use the higher of the two targets.
Powered DHW Demand
The control registers a DHW Demand when a voltage
between 20 and 260 V (ac) is applied across the DHW
Demand terminals 29 and 30. An aquastat or setpoint
control is used to switch the DHW Demand circuit. Program
a DHW Exchange temperature for the Occupied and
UnOccupied events in the Adjust Menu.
• DHW Sensor must be set to Off.
DHW Sensor
The control can register a DHW Demand when A DHW
Sensor is wired to terminals 5 and 6. Once the DHW Sensor
drops 1/2 of the DHW Differential setting below the DHW
Setpoint, the control registers a DHW Demand. Program a
DHW Tank temperature for the Occupied and UnOccupied
events in the Adjust Menu.
The DHW Sensor must be set to On. There cannot be
an externally powered DHW demand when using a
DHW sensor.
tN4 Setpoint Control in DHW Mode
The control can register a DHW Demand when a tN4
Setpoint Control in DHW Mode is wired to terminals 1 and 2.
The DHW Demand is sent over the tN4 communication bus
when the Setpoint Control calls for heat. Program a DHW
tank temperature for the Occupied and UnOccupied events
and the desired supply water temperature required on the
tN4 bus in the Adjust Menu of the tN4 Setpoint Control.
DHW Differential Setting in Adjust Menu
Due to large differences between the heating load and the
DHW load, a separate DHW differential should be used
whenever a DHW Demand is present. This will improve
staging and boiler cycling. When using a DHW Sensor, a
DHW Demand is registered when the DHW sensor drops 1/2
of the DHW Differential setting below the DHW setting. The
DHW Demand is satisfied once the DHW Sensor rises 1/2
of the DHW Differential setting above the DHW setting.
DHW
Differential
DHW Target
ON
OFF
•
Boiler Target Temperature during a DHW Demand
If a Powered DHW Demand is present, the boilers are
operated to maintain the DHW Exchange temperature. If a
DHW sensor demand is present, the boilers are operated
to maintain a temperature of 40°F (22°C) above the DHW
tank temperature. If a tN4 demand is present, the primary
pump is turned on according to the device’s reported
requirements and the boilers are operated to maintain the
devices requested target on the bus. The DHW Demand
overrides the boiler reset target temperature, except when
the boiler reset target is higher than the DHW target.
Regardless of DHW settings and requested targets, the
boilers will maintain a target temperature no higher than
the Boil MAX setting.
DHW During UnOccupied
When using a Powered DHW Demand, the control has a
DHW Exchange UnOccupied setting that allows the installer
to select On or Off. When set to On, and the control receives
a DHW Demand during an UnOccupied or Sleep period,
the control continues operation of the DHW system as it
would during the Occupied and Wake periods. When set to
Off, the control will ignore a DHW Demand for the duration
of the UnOccupied and Sleep periods.
When using a DHW Sensor, a second DHW temperature
setting is available for the UnOccupied or Sleep period.
DIP Switch must be set to Setback to view UnOccupied
items.
During the Away Scene, DHW demands are ignored.
DHW Mode Setting in the Adjust Menu
The control has six different DHW Modes that affect pump
operation. The required DHW Mode setting will depend on
the piping arrangement of the DHW tank and whether or
not priority for DHW is necessary. DHW Priority stops or
limits the delivery of heat to the building heating system
while the DHW tank calls for heat. This allows for quick
recovery of the DHW tank.
Mode OFF / No DHW Generation
All DHW demands are ignored. If this mode is selected
while DHW generation is underway, all DHW operation
ceases.

© 2012 D275 - 01/12 12 of 48
Mode 1 - DHW in Parallel with No Priority
When a valid DHW Demand is present, the DHW relay
(terminal 23) turns on. The primary pump can operate
when a Boiler Demand is present. It is assumed that the
DHW pump will provide adequate flow through the heat
exchanger and the boiler. Heating zones are unaffected
by DHW operation.
Mode = 1
DHW
Pump
Primary
Pump
Mode 2 - DHW in Parallel with Priority
When a valid DHW Demand is present, the DHW relay
(terminal 23) turns on. The primary pump can operate
when a Boiler Demand is present. If the boilers are unable
to maintain the boiler target temperature, space heating
zones are shut off sequentially using tN4 communication
in order to provide priority to the DHW tank. For non-tN4
systems, the primary pump shuts off to provide priority. It
is assumed that the DHW pump will provide adequate flow
through the heat exchanger and the boiler.
Mode = 2
DHW
Pump
Primary
Pump
OFF
Mode 3 - DHW in Primary/Secondary with No Priority
When a valid DHW Demand is present, the DHW relay
(terminal 23) and Primary Pump relay (terminal 24) turn
on. Heating zones are unaffected by DHW operation. This
mode can be used if the DHW tank is piped in parallel and
a DHW valve is installed (need to use an external relay to
power the valve with 24 V (ac) since the DHW pump output
is a 120 V (ac) powered output).
Mode = 3
DHW
Pump
Primary
Pump
Mode 4 - DHW in Primary/Secondary with Priority
When a valid DHW Demand is present, the DHW relay
(terminal 23) and Primary Pump relay (terminal 24) turn
on. If the boilers are unable to maintain the boiler target
temperature, space heating zones are shut off sequentially
using tN4 communication in order to provide priority to the
DHW tank. For non-tN4 systems, priority requires the use
of an external relay to force the heating zones off.
Mode = 4
OFF
DHW
Pump
Primary
Pump
Mode 5 - DHW in Parallel / Last Boiler with Priority
When a valid DHW Demand is present, the DHW relay
(terminal 23) turns on and boiler pump 4 turns off. The
control uses the DHW Exchange Supply Sensor in order
to measure the boiler supply temperature supplied to the
indirect tank. There are two boiler target temperatures, one
for the heating system (BOIL TARGET) and one for the
indirect DHW system (BOIL DHW TARGET). In this mode,
the DHW Demand can only be provided from an External
Powered Demand or tN4 Setpoint Control in DHW mode.
All boilers are used for space heating requirements
Boiler 4 is used for DHW when there is a DHW demand
The dedicated DHW boiler is always boiler 4 (relay 4),
even if there are less than 4 boilers.
If boiler 4 is disabled and mode 5 is selected then the
dedicated DHW boiler (boiler 4) will not operate.
Mode = 5
OFF
ON
DHW Pump
Primary
Pump
Boiler
Supply
Sensor
DHW Exchange
Supply Sensor
•
•
•
•

13 of 48 © 2012 D275 - 01/12
Mode 6 – Dedicated DHW
When a valid DHW Demand is present from the DHW
Sensor, the primary pump relay turns on. The DHW Relay
in this mode is used as the DHW recirculation pump and
operates continuously in the Occupied period and cycles
with the primary pump in the UnOccupied period. The boiler
plant is sequenced based only on the DHW Sensor.
All boilers are used for DHW requirements
Requires DHW demand from DHW sensor
DHW Pump Relay is used for DHW recirculation pump
Boiler Supply Sensor Not Required
Recirculation
Pump
DHW Sensor
On/
Off
On/
Off
Mode = 6
DHW Priority Override Setting in Adjust Menu
DHW Priority Override applies to DHW MODE 2 and 4, as
well as Mode 5 if there is a tN4 device with DHW. It prevents
the building from cooling off too much or the possibility of
a potential freeze up during DHW priority.
When set to auto, the priority time is calculated based
on outdoor temperature. At or below the design outdoor
temperature, 15 minutes are allowed for DHW priority.
At or above 70°F (21°C), 2 hours are allowed for DHW
priority. The time allowed for DHW priority varies linearly
between the above two points. There is a manual setting
also available in the adjust menu.
The priority timer does not start timing until priority is selected
and both a DHW Demand and a Boiler Demand exist together.
Once the allowed time for priority has elapsed, the control
overrides the DHW priority and resumes space heating.
Automatic Priority Override
15 mins
2 hours
Design Temperature
70°F (21°C)
Conditional DHW Priority
If the boiler supply temperature is maintained at or above
the required temperature during DHW generation, this
indicates that the boilers have enough capacity for DHW
and possibly heating as well. As long as the boiler supply
temperature is maintained near the target, DHW and heating
occurs simultaneously.
•
•
•
•
DHW Post Purge
After the DHW Demand is removed, the control performs
a purge. The control shuts off the boilers and continues to
operate the DHW Pump and the primary pump if applicable.
This purges the residual heat from the boilers into the
DHW tank. The control continues this purge until one of
the following occurs:
1. A Boiler Demand is detected
2. The boiler supply drops 20°F (11°C) below the DHW
target temperature
3. The DHW tank temperature rises above the DHW
setpoint plus 1/2 DHW Differential
4. Two minutes elapse
DHW Mixing Purge
After DHW operation, the boiler is extremely hot. At the same
time, the heating zones may have cooled off considerably
after being off for a period of time. When restarting the
heating system after a DHW demand with priority, the
control shuts off the boiler and continues to operate the
DHW pump while the primary pump is turned on. This allows
some of the DHW return water to mix with the cool return
water from the zones and temper the boiler return water.
DHW with Low Temperature Boilers
If DHW heating is to be incorporated into a low temperature
system such as a radiant floor heating system, a mixing
device is often installed to isolate the high DHW supply
temperature from the lower system temperature. If a mixing
device is not installed, high temperature water could be
supplied to the low temperature system while trying to
satisfy the DHW demand. This may result in damage to
the low temperature heating system.
The control is capable of providing DHW heating in such a
system while minimizing the chance that the temperature
in the heating system exceeds the design supply water
temperature. In order to do this, the following must be true:
tN4 Present
DHW MODE 2 or 4
Boil MIN OFF
On a call for DHW, the control provides DHW priority by
sending a message on the boiler temperature bus to the tN4
thermostats to shut off the heating zones for a period of time.
The length of time is based on the outdoor air temperature as
described in the DHW Priority Override section. However, if
the DHW Demand is not satisfied within the allotted time, the
boiler shuts off and the heat of the boiler is purged into the
DHW tank. A DHW mixing purge occurs in order to reduce
the boiler water temperature and once the boiler supply
temperature is sufficiently reduced, the DHW Pump contact
shuts off. The heating system zones are allowed to turn on for
a period of time to prevent the building from cooling off. After
a period of heating, and if the DHW Demand is still present,
the control shuts off the heating system and provides heat
to the DHW tank once again.
DHW Boilers Setting in Adjust Menu
Select the number of boilers to use for DHW generation.
•
•
•

© 2012 D275 - 01/12 14 of 48
Setpoint Operation Section J
Setpoint operation is only available when DHW Mode is
set to Off.
The control can operate to satisfy the requirements of a
setpoint load in addition to a space heating load. A setpoint
load overrides the current outdoor reset temperature in
order to provide heat to the setpoint load.
Setpoint Demand
Setpoint Demands come from one of two sources: a
Powered Setpoint Demand, or a tN4 Setpoint Control.
Powered Setpoint Demand
The control registers a Setpoint Demand when a voltage
between 20 and 260 V (ac) is applied across the Setpoint
Demand terminals 29 and 30. An aquastat or setpoint
control is used to switch the Setpoint Demand circuit.
Program a Setpoint target for the Occupied and UnOccupied
events in the Adjust Menu.
• DHW Mode must be set to Off.
tN4 Setpoint Control
The control can register a Setpoint Demand when a tN4
Setpoint Control is wired to terminals 1 and 2. The Setpoint
Demand is sent over the tN4 communication bus when
the Setpoint Control calls for heat. Program a Setpoint
temperature for the Occupied and UnOccupied events and
the desired supply water temperature required on the tN4
bus in the Adjust Menu of the tN4 Setpoint Control.
• DHW Mode must be set to Off.
A demand from a tN4 Setpoint Control can coexist with another
setpoint demand without generating an error message. The
275 will then use the higher of the two targets.
Boiler Target Temperature during a Setpoint Demand
If a Powered Setpoint Demand is present, the boilers are
operated to maintain the Setpoint target. If a tN4 demand
is present, the primary pump is turned on according to
the device’s reported requirements and the boilers are
operated to maintain the devices requested target on the
bus. The Setpoint Demand overrides the boiler reset target
temperature, except when the boiler reset target is higher
than the Setpoint target. Regardless of Setpoint settings
and requested targets, the boilers will maintain a target
temperature no higher than the Boil MAX setting.
Setpoint During UnOccupied
When using a Powered Setpoint Demand, the control has
a Setpoint UnOccupied setting that allows the installer to
select On or Off. When set to On, and the control receives
a Setpoint Demand during an UnOccupied or Sleep period,
the control continues operation of the Setpoint system as
it would during the Occupied and Wake periods. When set
to Off, the control will ignore a Setpoint Demand for the
duration of the UnOccupied and Sleep periods.
DIP Switch must be set to Setback to view UnOccupied
items.
During the Away Scene, Setpoint demands are ignored.
Setpoint Mode Setting in the Adjust Menu
The control has four different Setpoint Modes that affect
pump operation. The required Setpoint Mode setting will
depend on the piping arrangement and whether or not
priority is necessary. Setpoint Priority stops or limits the
delivery of heat to the building heating system while the
Setpoint load calls for heat. This allows for quick recovery
of the Setpoint load.
Mode OFF - No Setpoint Operation
All Setpoint demands are ignored. If this mode is selected
while Setpoint operation is underway, all Setpoint operation
ceases.
Mode 1 - Setpoint in Parallel with No Priority
Whenever a Setpoint Demand is present, the boilers are
operated to maintain the setpoint target. The primary
pump does not turn on, but may operate based on a Boiler
Demand. It is assumed that the Setpoint pump will provide
adequate flow through the heat exchanger and the boiler.
Primary
Pump
Setpoint
Mode = 1
Mode 2 - Setpoint in Parallel with Priority
When a Setpoint Demand is present, the boilers are
operated to maintain the setpoint target. The primary
pump can operate when a Boiler Demand is present. If the
boilers are unable to maintain the boiler target temperature,
space heating zones are shut off sequentially using tN4
communication in order to provide priority to the Setpoint
Load. For non-tN4 systems, the primary pump shuts off to
provide priority. It is assumed that the Setpoint pump will
provide adequate flow through the heat exchanger and
the boiler.
Setpoint
Primary
Pump
OFF
Mode = 2

15 of 48 © 2012 D275 - 01/12
Mode 3 - Setpoint in Primary/Secondary with No Priority
Whenever a Setpoint Demand is present, the primary pump
is turned on and the boilers are operated to maintain the
setpoint target.
Primary
Pump
Setpoint
Mode = 3
Mode 4 - Setpoint in Primary/Secondary with Priority
Whenever a Setpoint Demand is present, the primary pump
is turned on and the boilers are operated to maintain the
setpoint target. Space heating zones will be shut off if the
boilers are unable to maintain the boiler target temperature
using tN4 communication. For non-tN4 systems, an external
relay is required to force off the heating zones.
Setpoint
Primary
Pump
OFF
Mode = 4
Setpoint Priority Override Setting in Adjust Menu
Setpoint Priority Override applies to SETPOINT MODE 2 and
MODE 4. To prevent the building from cooling off too much or
the possibility of a potential freeze up during setpoint priority,
the control limits the amount of time for setpoint priority.
When set to auto, the priority time is calculated based
on outdoor temperature. At or below the design outdoor
temperature, 15 minutes are allowed for Setpoint priority. At or
above 70°F (21°C), 2 hours are allowed for Setpoint priority.
The time allowed for Setpoint priority varies linearly
between the above two points. There is a manual setting
also available in the adjust menu.
The priority timer does not start timing until priority is
selected and both a Setpoint Demand and a Boiler Demand
exist together. Once the allowed time for priority has
elapsed, the control overrides the Setpoint priority and
resumes space heating.
Automatic Priority Override
15 mins
2 hours
Design Temperature70°F (21°C)
Conditional DHW Priority
If the boiler supply temperature is maintained at or above
the required temperature during setpoint generation, this
indicates that the boiler has enough capacity for setpoint
and possibly heating as well. As long as the boiler target
temperature is maintained, setpoint and heating occur at
the same time.
Setpoint Post Purge
After a tN4 Setpoint Demand is removed, the control
performs a purge. The control shuts off the boilers and
continues to operate the Setpoint Pump and the primary
pump if applicable. This purges the residual heat from the
boilers into the Setpoint load. The control continues this
purge until one of the following occurs:
1. A Boiler Demand is detected
2. The boiler supply drops 20°F (11°C) below the Setpoint
target temperature
3. Two minutes elapse

© 2012 D275 - 01/12 16 of 48
Energy Management System (EMS) Section K
The control can accept an external DC signal from an Energy
Management System (EMS) in place of the outdoor sensor.
The control converts the DC signal into the appropriate
boiler target temperature between 50°F (10°C) and 210°F
(99°C) based on the EMS Input Signal and Offset settings.
To use the external input signal, the EMS / Demands DIP
switch must be set to EMS.
An external signal is generated by applying a voltage
between 0 V (dc) and 10 V (dc) across the Out + and Com
– terminals (3 and 2). Voltages that exceed 10 V (dc) will
still be considered a 10 V (dc) signal.
Once voltage is applied, the EMS Input Signal pointer is
displayed in the LCD and the control calculates a boiler
target and closes the primary pump contact. The control
then modulates the boiler(s), if required, to maintain the
target supply temperature.
If the EMS signal goes below the minimum voltage, the
EMS Input Signal pointer is turned off in the display. The
boiler target temperature is displayed as “– – –” to indicate
that there is no longer a call for heating.
Input Signal
The control can accept either a 0 - 10 V (dc) signal or a
2 - 10 V (dc) signal. The External Input Signal setting must
be set to the proper setting based on the signal that is being
sent to the control.
0 - 10 V (dc) or 0 - 20 mA
When the 0 - 10 V (dc) signal is selected, an input voltage
of 1 V (dc) corresponds to a boiler target temperature of
50°F (10°C). An input voltage of 10 V (dc) corresponds
to a boiler target temperature of 210°F (99°C). As the
voltage varies between 1 V (dc) and 10 V (dc) the boiler
target temperature varies linearly between 50°F (10°C) and
210°F (99°C). If a voltage below 0.5 V (dc) is received the
boiler target temperature is displayed as “– – –” indicating
that there is no longer a call for heating.
A 0 - 20 mA signal can be converted to a 0 - 10 V (dc) signal
by installing a 500  resistor between the Out + and Com
– terminals (3 and 2).
2 - 10 V (dc) or 4 - 20 mA
When the 2 - 10 V (dc) signal is selected, an input voltage
of 2 V (dc) corresponds to a boiler target temperature of
50°F (10°C). An input voltage of 10 V (dc) corresponds
to a boiler target temperature of 210°F (99°C). As the
voltage varies between 2 V (dc) and 10 V (dc) the boiler
target temperature varies linearly between 50°F (10°C) and
210°F (99°C). If a voltage below 1.5 V (dc) is received the
boiler target temperature is displayed as “– – –” indicating
that there is no longer a call for heating.
A 4 - 20 mA signal can be converted to a 2 - 10 V (dc) signal
by installing a 500  resistor between the Out + and Com
– terminals (3 and 2).
CONVERSION TABLE 0 - 10
0 - 20 mA* 0 - 10 V (dc) Boiler Target
0 0 – – – (OFF)
2 1 50°F (10°C)
4 2 68°F (20°C)
6 3 86°F (30°C)
8 4 103°F (39°C)
10 5 121°F (49°C)
12 6 139°F (59°C)
14 7 157°F (69°C)
16 8 174°F (79°C)
18 9 192°F (89°C
20 10 210°F (99°C)
*Requires 500 ΩResistor in Parallel
*Requires 500 ΩResistor in Parallel
CONVERSION TABLE 2 - 10
4 - 20 mA* 2 - 10 V (dc) Boiler Target
0 0 – – – (OFF)
4 2 50°F (10°C)
6 3 70°F (21°C)
8 4 90°F (32°C)
10 5 110°F (43°C)
12 6 130°F (54°C)
14 7 150°F (66°C)
16 8 170°F (77°C)
18 9 190°F (88°C)
20 10 210°F (99°C)
Offset Setting in Adjust Menu
For external input operation, the boiler target (determined
from the external input signal) may be fine tuned. The
Offset setting is used to provide the fine tuning. The Offset
setting may be adjusted ±10°F. When set to 0°F, if the
temperature determined from the external signal is 140°F,
the boiler target will be 140°F. When set to +5°F and with
the same external signal represents 140°F, the boiler target
will be 145°F.
Example
Range = 0 - 10 V (dc)
Input = 7 V (dc) 157°F (69°C)
Offset = +5°F (3°C) +5°F (3°C)
Boiler Target = 162°F (72°C)
The minimum and maximum settings also apply for external
input operation. For example, if a boiler minimum of 140°F
is set and the external signal received represents 80°F, the
boiler target will be 140°F. The MIN segment will also be
displayed to indicate that a limiting condition is in effect.
This also applies for the MAX segment limit.
Whenever an external signal is used, the control can still
provide all DHW OR Setpoint functions.

17 of 48 © 2012 D275 - 01/12
Pump Operation Section L
Primary Pump Operation
The control includes two primary pump outputs with
capability for sequencing. Primary pump sequencing is
activated through a DIP switch. Only primary pump 1
is operated when pump sequencing is turned off, while
primary pumps 1 and 2 are operated in stand-by mode
when pump sequencing is turned on.
The running times of the primary pumps are logged in the
view menu. To reset these values back to zero, press and
hold the up and down button while viewing this item.
Note: Once primary pump sequencing is selected, DHW
operation is not available. Setpoint operation, however, is
available if primary pump sequencing is selected.
The primary pump(s) will operate when the control receives
an appropriate demand:
External Boiler Demand
tN4 Boiler Demand and that zone’s thermostat has H1
Pump set to On.
DHW Demand and the control is set to DHW Mode 3,
4, or 6.
Setpoint Demand and the control is set to Setpoint Mode
3 or 4.
The primary pump also operates when the control is
completing a DHW Purge.
tN4 thermostats can select whether the primary pump is
required to operate or not. tN4 thermostats also include a
thermal actuator setting which can delay the primary pump
for 3 minutes to allow thermal actuators to open.
Flow Proof
The control includes a flow proof demand in order to prove
flow once a primary pump has turned on. In order for
boiler operation to commence, the proof demand must be
present. A flow proof signal is required at all times during
pump operation. A flow proof is generated by applying a
voltage between 20 and 260 V (ac) across the Flow Proof
terminals (30 and 31). Once voltage is applied, the Proof
Demand indicator is turned on in the LCD.
Once a pump contact is turned on, a flow proof signal must
be present before the flow proof delay has expired.
The flow proof demand is selected by setting the Proof
Demand item in the Adjust menu to F P (flow proof).
A flow proof demand can come from a flow switch, pressure
differential switch, current sensing or power sensing device.
DemDem Pr.Com 3130
L
N
20 to 260 V (ac)
∆P Pressure Differential Switch
FS Flow Switch
KW Power Sensing Device
Amp Current Sensing Device
•
•
•
•
Stand-by Operation
The control only operates one primary pump at a time. A
flow proof device can be used to detect when stand-by
pump operation is required.
When a demand is registered, the lead pump is activated,
and the control waits for flow to be established within the
flow proof delay time.
If no flow is established, the lead pump is de-activated,
the lag pump is activated and the control waits again for
the flow to establish within the flow proof delay time.
If again no flow is established, the lag pump is de-activated
and the control stops operation until the error is cleared.
Verify that the pumps and flow proof device are working
correctly before clearing the error.
If the lead pump establishes flow, and fails during
operation, the lag pump is activated.
If at any time, one or both pumps fail to prove flow, an
error message is displayed.
Normal Operation
On
Flow Proof
Device
Off
275
Stand-by Pump Operation
Failed
Optional
Alert
Flow Proof
Device
On
275
Flow Proof Delay Setting in Adjust Menu
The control waits a period of time to receive a flow proof
demand from the time the primary pump turns on. If the
control does not receive a flow proof demand within that
period of time, the primary pump turns off and the stand-by
primary pump (if active) turns on. The control then waits
that period of time again for the stand-by primary pump to
prove flow. If flow is not proven, the stand-by pump turns
off. The period of time is set through the Proof Demand
‘Pump’ DLY item in the Adjust menu and it is adjustable
between 10 seconds and 3 minutes.
•
•
•
•
•

© 2012 D275 - 01/12 18 of 48
Flow Proof Demand Test
The control includes a flow proof demand test in order to
determine if the flow/pressure device has failed. A flow
proof failure is detected if a flow proof is present after the
pumps have been shut off for more than four minutes. This
can occur if the flow proof device sticks in the on position
even when flow has stopped in the system. A proof demand
error will latch when this condition exists.
Primary Pump Rotation Setting in Adjust Menu
The control rotates the pumps based on the Rotate item
in the Adjust menu. Frequency of Rotation is based on the
running time of the pumps. Rotation is done when the lead
pump is off. If the lead pump runs continuously, the rotation
is delayed for up to 12 hours. If the pump runs continuously
and rotation is required, the control shuts off the lead pump
and 1 second later the stand-by pump is turned on. This
eliminates overloading the pump electrical circuit. Upon
turning on the stand-by pump the flow proof input is checked
after the flow proof demand delay time.
Primary Pump Purge
After the last valid demand is removed, the primary pump
is operated for an additional purging time of at least 20
seconds. If the last demand came from a tN4 zone, the
control sends out a purge message to override the zone
open for the duration of the boiler purge. At the end of
the purge, the zone override is removed so the zone is
allowed to close and turn off the primary pump. If the last
demand came from a non-tN4 zone, the purge period for
the primary pump is adjustable between 10 seconds and
19:55 minutes.
Boiler Pump Operation
The control is capable of operating individual boiler pumps.
This feature is available by setting the Boiler relays to pump
in the Adjust Menu.
The control includes a boiler pump pre-purge which operates
the respective boiler pump for a period of time before the
boiler is ignited in order to purge potential residual heat out
of the boiler. The pre-purge time is determined from the
boiler mass setting. As the boiler mass setting is increased,
the boiler pump pre-purge time is also increased. The
pre-purge time is fixed at 4 seconds whenever a DHW /
Setpoint demand is provided in order to reduce boiler pick-
up times.
The control includes a boiler pump post-purge feature that
operates the respective boiler pump for a period of time
after the boiler is turned off. This feature will purge heat out
of the boiler and aid in reducing “kettling”. The amount of
time for the boiler pump post purge is adjustable between
10 seconds and 19:55 minutes. See the boiler pump purge
setting in the adjust menu.
Combustion Air and Alert Settings Section M
Relay Setting in Adjust Menu (C.A. / Alert)
The control includes an auxiliary relay that can be used
either for a combustion / venting device or an Alert. Selection
is made through the Relay item in the Adjust menu.
Alert
When the Relay is set to Alert, terminals 21 and 22 close
whenever a control or sensor error is detected, or when a
warning or limiting condition is detected. When the alert
contact closes, refer to the Error Messages section of this
brochure to determine the cause of the alert and how to
clear the error.
Boiler Alarm
For the Boiler Alarm item to appear in the Adjust menu,
the Relay must be set to Alert. If no temperature increase
is detected at the boiler supply sensor within this delay
period, the Alert relay will close and the control will display
the Boiler Alarm error message. To clear the error, press
and hold the up and down buttons together for 5 seconds
while viewing the error message in the View menu.
Combustion Air (C.A.)
When the Relay is set to C.A., terminals 21 and 22 operate
a combustion air damper / fan motor or power vent motor.
The Relay closes once a demand is received and the
control has determined that one or more boilers need to
be turned on.
Combustion Air Proof Demand Setting in Adjust Menu
The proof demand can be used to prove a combustion air
or venting device if set to C.A. Boiler operation cannot occur
until the proof demand is present. If the proof demand is
lost during operation, the boiler plant is sequenced off.
Combustion Air Proof Demand Delay Setting in
Adjust Menu
The control includes a time delay that is associated with
the proof demand feature in order to determine if the proof
device is functional. Once the C.A. relay closes, the control
allows for this delay to receive the proof demand. If the proof
demand is not received within the delay time, the control
will display an error message.
Combustion Air Delay Setting in Adjust Menu
If the Proof Demand function is set to F P (flow proof) or
OFF, sequencing only occurs once a user adjustable time
delay elapses.
Combustion Air Post Purge
There is a fixed 15 second post purge of the C.A. relay
after the last boiler has turned off, or demand is removed. If
there is a heat demand still present once the last boiler has
turned off, the control can look at the error and determine
if sequencing is to occur in a “short” period of time. If the
control does anticipate staging, the C.A. relay will remain
on. Otherwise, the C.A. relay will be turned off once the 15
second post purge elapses.

19 of 48 © 2012 D275 - 01/12
Setting the Schedule Section N
To provide greater energy savings, you can operate the
control on a programmable schedule. The schedule is
stored in memory and is not affected by loss of power to the
control. If a tN4 network is detected the control can become
either a schedule member or schedule master.
Control (CTRL) Schedule (tN4 present)
The schedule only applies to the control. The control follows
its own schedule and the events are not communicated to
tN4 thermostats.
Master Schedule (tN4 present)
If the control is connected to tN4 thermostats, then the
control can operate on a master schedule. You can set up
a maximum of four master schedules on the tN4 Network.
A master schedule is available to all devices on the tN4
network. Master schedules simplify installation since one
master schedule may be used by multiple devices.
To create a master schedule:
Assign the control to be a schedule master by setting
the Heat Schedule item in the Schedule menu to Master
(MST) 1 to 4. After a master schedule is selected, a clock
symbol will appear in the View menu display.
Note: The 275 Setback /Off DIP Switch must be set to
Setback to access the Schedule Menu.
To follow a master schedule:
Assign the control to follow a master schedule by setting
the Heat Schedule in the Schedule menu to Member
(MBR) 1 to 4.
Master
Schedule 1
Member of
Schedule 1 Members of Schedule 2
Master
Schedule 2
None Zone
Schedule
23 4 56
275
Zone 1
•
•
Schedule Types
The schedule type determines when the schedule repeats
itself. This control includes three schedule types:
• 24 Hour: Repeats every 24 hours.
• 5-11: Repeats on a weekly basis. However, it breaks the
week into Saturday and Sunday followed by the weekdays.
This reduces the amount of schedule event settings.
• 7 Day: Repeats on a weekly basis and allows for separate
event times for each day.
Schedule Type
Day 24 Hour 5-11 7 day
Saturday
•
• •
Sunday
• •
Monday
•
•
Tuesday
•
Wednesday
•
Thursday
•
Friday
•
Schedule Mode
The schedule mode can have either 4 or 2 events per day.
An event is a time at which the control changes the target
temperature. The event time can be set to the nearest 10
minutes. If you wish to have the thermostat skip the event,
enter “--:--“ as the time. The “--:--“ time is found between
11:50 PM and 12:00 AM. See the table, Schedule Mode,
for more details regarding types of events.
Schedule Mode Event 24Hr Sat Sun Mon Tue We Thu Fri
4 events per day
Wake 6:00 AM 6:00 AM 6:00 AM 6:00 AM 6:00 AM 6:00 AM 6:00 AM 6:00 AM
Unoccupied 8:00 AM 8:00 AM 8:00 AM 8:00 AM 8:00 AM 8:00 AM 8:00 AM 8:00 AM
Occupied 6:00 PM 6:00 PM 6:00 PM 6:00 PM 6:00 PM 6:00 PM 6:00 PM 6:00 PM
Sleep 10:00 PM 10:00 PM 10:00 PM 10:00 PM 10:00 PM 10:00 PM 10:00 PM 10:00 PM
or
2 events per day Occupied 6:00 AM 6:00 AM 6:00 AM 6:00 AM 6:00 AM 6:00 AM 6:00 AM 6:00 AM
Unoccupied 10:00 PM 10:00 PM 10:00 PM 10:00 PM 10:00 PM 10:00 PM 10:00 PM 10:00 PM
Combustion Air Proof Demand Test
The control includes a C.A. proof demand test in order to
determine if the proving device has failed. If the C.A. damper
contacts are opened, the flow proof demand should not be
present after 4 minutes. If the flow proof demand remains,
the control will display an error message.

© 2012 D275 - 01/12 20 of 48
Boost Section P
When the control changes from the UnOccupied mode
to the Occupied mode, it enters into a boosting mode. In
this mode, the supply water temperature to the system
is raised above its normal values for a period of time to
provide a faster recovery from the setback temperature of
the building. The maximum length of the boost is selected
using the BOOST setting in the Adjust menu.
Typical settings for the boost function vary between 30
minutes and two hours for buildings that have a fast
responding heating system. For buildings that have a
slow responding heating system, a setting between four
hours and eight hours is typical. After a boost time is
selected, the setback timer must be adjusted to come out
of setback some time in advance of the desired occupied
time. This time in advance is normally the same as the
BOOST setting.
If the building is not up to temperature at the correct time,
the BOOST setting should be lengthened and the setback
timer should be adjusted accordingly. If the building is
up to temperature before the required time, the BOOST
setting should be shortened and the setback timer should
be adjusted accordingly. If the system is operating near
its design conditions or if the supply water temperature
is being limited by settings made in the control, the time
required to bring the building up to temperature may be
longer than expected.
tekmarNet®4 Communication Section R
tekmarNet
®
4 (tN4) communicates between tN4 devices
(thermostats, Reset Module and Expansion Modules). Each
tN4 device is connected to a tN4 communication bus using
two wires. Each tN4 bus adjusts a single water temperature
in the system using indoor temperature feedback. The
Boiler Control 275 allows for one tN4 bus. This allows you
to control a system with one water temperature. A system
that has more than one tN4 bus is referred to as a tN4
network.
Bus 1
Network
tekmarNet®4
Thermostats
275
Boiler Control 275
The Boiler Control 275 is the system control for a hydronic
heating system. The 275 operates up to 4 modulating boilers,
a domestic hot water tank, and responds to other heating
requirements such as pool heating and snow melting. The
275 also coordinates and optimizes the operation of all the
tN4 thermostats.
tN4 Thermostat
The tN4 thermostat operates heating, cooling, and or
ventilation equipment for a zone. Several tN4 thermostats
may work in a group when operating a cooling system. Up
to 24 tN4 devices can connect to a single tN4 bus.
The control will exercise the Combustion Air Damper, all
pumps, and tN4 zones (zone valves and zone pumps) for
10 seconds every three days of inactivity to prevent seizure.
To enable exercising, switch the Exercise / Off DIP to the
Exercise position.
The control has a built-in time clock to allow the control to
operate on a schedule. A battery-less backup allows the
control to keep time for up to 4 hours without power. The
time clock supports automatic adjustment for Daylight
Saving Time (DST) once the day, month, and year are
entered. Use the Time menu to set the correct time, day,
month, and year.
Note: The Setback / Off DIP Switch must be set to Setback
before the Time menu can be accessed.
Time Clock Section O
Daylight Savings Time Modes
Mode DST Start DST End
1 1st Sunday in April Last Sunday in October
2 2nd Sunday in March 1st Sunday in November
The control will exercise the Combustion Air Damper, all
pumps, and tN4 zones (zone valves and zone pumps) for
10 seconds every three days of inactivity to prevent seizure.
To enable exercising, switch the Exercise / Off DIP to the
Exercise position.
Exercising Section Q