Tekmar DHW Control 252 User manual

C
17 18
Sen
10K
0.4
2.0
3.6
Heating Curve
22°F
242
Dem R
12 5678
Pmp
Two Stage Boiler & DHW Control 252
Dem
Heat System
Pmp
11 12 19
Com
Sw
UnO
20 21
SenSup
140°F
80 200
DHW
120°F
Off 170
Minimum
Supply Boiler Differential
80
Power Supply: 24V 60Hz 3VA
Relay capacities: 24V 10A
Test
No power here
Maximum 24 volts
Dem
34
Dem Stage Sen
Occupied
35
(2) 105 (41)
70°F
(21°C)
Unoccupied
35
(2) 105 (41)
70°F
(21°C)
H1072
Date
S/N 1492 1234567
11
13 14
Stage
22
Power
Heat
Demand
DHW
Demand
WWSD
Stage 1 Stage 2
UnOcc.
Minimum
12345678
Auto
Stage
1 2
Perm. Heat Demand
External Heat Demand
Indoor sensor
Zone control
DHW during unoccupied
DHW priority
Rotate
Off
910
Pmp
DHW
Pmp
DHW
15 16
Sen
DHW
22
Out
Sen
Com
Sen
RTU
2K
DHW valve
DHW pump
DHW
pump
System
pump
Power
- Data Brochure
Two Stage Boiler & DHW Control 252
The tekmar Two Stage Boiler & DHW Control 252 is a microprocessor-based control
which regulates the supply water temperature from one or two boilers by turning them
on or off. The supply temperature is based on the outdoor, and optionally, the indoor
airtemperatures. When DomesticHotWater(DHW)isrequired,thecontrolwilloperate
the boiler(s) to regulate the supply water temperature in order to satisfy the DHW
requirements.
D 252
Operating Mode
selector switches
Terminal Plugs:
Power and out-
put connections
Terminal Plug:
Sensor and
timer inputs
Outdoor Reset Strategy . . pg. 2 Testing . . . . . . . . . . . . pg. 10
Sequence of Operation . . pg. 3 Error Messages . . . . . pg. 11
Installation . . . . . . . . . . . . pg. 4 Technical Data . . . . . . pg. 12
Settings . . . . . . . . . . . . . . . pg. 7 Limited Warranty . . . . pg. 12
10/92
Heating
is required 24Vac power
supply is on
System is in
Warm Weather
Shut Down
System is
switched to
Unoccupied
Control is
maintaining
Minimum Supply
DHW
pump or valve
is on
DHW
is required
System Pump
is on
Occupied
temperature
setting
Heating Curve
setting
DHW
temperature
setting
Boiler
Differential
setting
Minimum
Supply setting
Test button &
LED to test
main control
functions
Stage 2 is on
Stage 1 is on
Unoccupied
temperature
setting
Input: 2K RTU
Optional
Input:
Indoor Sensor
074 Optional
Input:
Unoccupied
signal.
Optional
Input: DHW Sensor
071 Optional
Output: Turn
on stage #1 Output: Turn on stage #2
Output: Turn on
System Pump Output: Turn on
DHW Pump / Valve
24Vac power supply
Note: Wiring
is detailed in
Application
Brochure
A 252
Input: Outdoor
Sensor 070
Included
Input: Universal
Sensor 071. Included
Input:
Heat Demand
signal. Optional
Input: DHW Demand
signal. Optional
Two Stage Boiler & DHW Control 252
Power
Heat
Demand
WWSD
UnOcc.
Minimum
Stage 1
Occupied
35
(2) 105 (41)
70°F
(21°C)
Unoccupied
35
(2) 105 (41)
70°F
(21°C)
Stage 2
System
Pump
DHW
Demand
DHW
Pump

Shifting the Heating Curve
(a) Manually, at the control:
The Occupied and Unoccupied dials on this control can shift the WWSD
point up or down from 35 to 105°F (2 to 41°C).
(b) Automatically, using room temperature feedback:
InadditiontoaSupplySensorandanOutdoorSensor,thiscontrolcanuse
atekmarRTU,ZoneControlorIndoorSensortoprovideroomtemperature
feedback for added comfort and system flexibility.
The control still calculates a desired supply temperature based on the
Heating Curve setting and the outdoor temperature.
Iftheairtemperatureintheroomistoocold,thecontrolwillshifttheHeating
Curve(andWWSDpoint)
up, whichraisesthesupplytemperatureuntil the
room warms up again.
Iftheairtemperatureintheroomistoowarm,thecontrolwillshifttheHeating
Curve(and WWSD point) down, which lowers thesupply temperature until
the room cools down.
Correct setting and shifting of the Heating Curve... the key to More Comfort and Energy Savings.
Heating Curve
As outdoor temperatures become colder, heat losses from a building increase, which requires the addition of more heat to prevent
theindoorairtemperaturefromalsobecomingcolder. Thistekmarresetcontrolmeasurestheoutdoortemperatureandastheoutdoor
temperature becomes colder, it balances the heat loss by making the heating supply water hotter.
The Heating Curve is used to calculate exactly how hot to make the supply water at different outdoor temperatures. It determines
the number of degrees the supply water temperature is raised for each degree the outdoor temperature falls.
Setting the Heating Curve
Two examples of how the Heating Curve works are illustrated in the following diagram.
—With a 2.4 Curve, the supply water temperature is raised 2.4 degrees for every degree of outdoor temperature drop.
If: WWSD point = 70°F and Outdoor temperature = 30°F, then supply temperature = 166°F
—With a 0.6 Curve, the supply water temperature is raised 0.6 degrees for every degree of outdoor temperature drop.
If: WWSD point = 70°F and Outdoor temperature = 30°F, then supply temperature = 94°F
2
• If the Heating Curve selected is too low; the heating system will not
supply hot enough water to keep the room temperature warm during
colder weather.
• If the Heating Curve selected is too high; the supply water will be too hot
for the conditions and the building will overheat during colder weather.
Warm Weather Shut Down (WWSD)
At warm outdoor temperatures, the indoor space of a building gains heat
fromtheoutdoors;additionalheatisnotrequired,andiftheheatingsystem
is running (even on standby), enough excess heat can be produced to
overheat the building, causing discomfort and wasting valuable energy.
This control shuts off the boiler(s) and system pump when the outdoor
temperature is above the WWSD point.
As outdoor temperatures get colder, there comes a point where the heat
gainturnsintoheatloss;the heat loss causes theindoortemperaturetofall
below the comfort level, and the heating system must be turned on to start
delivering heat.
Refer to the tekmar Essays E 001 and E 002 for more detailed information regarding control strategy and integration of control functions.
A very cool room temperature can shift the curve far enough up to bring the control out of WWSD at warm outdoor temperatures.
A very warm room temperature can shift the curve far enough down to put the control into WWSD at cool outdoor temperatures.
Toprovideheattothebuilding,thiscontrolturnsonthesystempumpandcyclestheboiler(s)todeliverheatatthelowoutputrequired
by the Heating Curve near the WWSD point.
When the system is operating near the WWSD point and the building is too cold; the WWSD point should be raised.
When the system is operating near the WWSD point and the building is too warm; the WWSD point should be lowered.
Outdoor Reset Strategy
Outdoor air temperature
Supply water temperature
50
(10) 30 (-1) 10 (-12) -10°F (-23)°C
110
(43)
70
(21)
70
(21)
90
(32)
210
(99)
170
(77)
150
(65)
130
(54)
190
(88)
3.6 3.0 2.4 2.0 1.6
0.8
0.4
1.0
0.6
90
(32)
50°F
(10)°C
Heating
Curve
WWSD
Point
1.2
Outdoor air temperature
Supply water temperature
50
(10) 30 (-1) 10 (-12) -10°F (-23)°C
110
(43)
70
(21)
70
(21)
90
(32)
210
(99)
170
(77)
150
(65)
130
(54)
190
(88)
3.6 3.0 2.4 2.0 1.6
0.8
0.4
1.0
90
(32)
50°F
(10)°C
Heating
Curve
WWSD
Point
will
shift
up and
down
with
shift of
Heating
Curve
1.2
UP DOWN
UP DOWN
Parallel Shift of Heating Curve
0.6

Heating Operation
Heat Demand signal Selector switch = External Heat Demand
(a) - A heat demand signal is caused by either 24Vac applied to terminals Heat Dem — Heat Dem
(1and2),ora10KZoneControlconnectedtoterminals10KSen—ComSen(19and20),orboth.
(b) -Aheatdemandsignaliseithercontinuouslypresentor,whena10K Zone Control is connected,
then a heat demand signal is only present when the Zone Control calls for heat.
tekmar Zone Control function Selector switch = Zone Control
The control will monitor the indoor temperatures of all zones, as well as the outdoor and supply
temperatures, andshifttheHeatingCurve (and the WWSDpoint)upordowntofineadjust the system
supply water temperature for whichever zone requires the hottest supply water. The Occupied and
Unoccupied dials are not functional.
Occupied/Unoccupied dial function (no indoor temperature feedback)
The control will monitor the outdoor and supply temperatures. The Occupied or Unoccupied dial settings become the WWSD point.
When the outdoor temperature is warmer than the setting of the Occupied dial, the control enters WWSD. When switched into
Unoccupied mode, the "Unoccupied' light will come on, and the control will operate at the temperature of the Unoccupied dial setting.
With Heat demand signal
The"HeatDemand"lightwillcomeon,thecontrolwillswitchonthesystempumpandcalculatethedesiredsupplytemperaturebased
on the requirements of the Heating Curve or the Minimum Supply setting, whichever is highest.
3
Sequence of Operation
When the Two Stage Boiler & DHW Control 252 is powered-up, the "Power" light will come on and the control will cycle through an
automatic test routine described in detail on pages 10 and 11 of this brochure. When the test routine is completed and no errors are
detected, the control exits the test routine and enters the operating mode.
Once in operating mode, the control uses the Outdoor Sensor 070 to continually monitor the outdoor temperature and the Universal
Sensor071tocontinuallymonitorthesystemsupplywatertemperature. AnoptionalUniversalSensor071canbeinstalledtoallowthe
control to monitor a DHW tank temperature.
Indoor temperature can be monitored through the use of;
(a) - a tekmar Zone Control (switch selector switch to "Zone Control" position), or;
(b) - an Indoor Sensor 074 or a tekmar 2k RTU (switch selector switch to "Indoor Sensor" position).
While monitoring all of these temperatures, the control recognizes the following temperature conditions and inputs and will respond as
described. During operation, the lights of the control will indicate operational status as illustrated.
WWSD function
When WWSD occurs, the "WWSD" light will come on, and the control will continue to
monitor the outdoor temperature, supply temperature and indoor temperature (optional).
Whenever 3 days pass with the control in uninterrupted WWSD, the system pump will be
cycled on for 20 seconds to help prevent it from seizing up.
Outdoor temperature cold enough to require heating
No heat demand signal
Whenthe outdoor temperature iscolder than the WWSDpoint, the control willleave WWSD.
Whenever the control leaves WWSD, the "WWSD" light will turn off and the control will
continue to monitor the outdoor temperature, supply temperature and indoor temperature
(optional), but no further control action will take place until there is a heat demand signal.
Power
Heat
Demand
DHW
Demand
WWSD
Stage 1 Stage 2
UnOcc.
Minimum
DHW
pump
System
pump
Power
Heat
Demand
DHW
Demand
WWSD
Stage 1 Stage 2
UnOcc.
Minimum
DHW
pump
System
pump
Power
Heat
Demand
DHW
Demand
WWSD
Stage 1 Stage 2
UnOcc.
Minimum
DHW
pump
System
pump
Power
Heat
Demand
DHW
Demand
WWSD
Stage 1 Stage 2
UnOcc.
Minimum
DHW
pump
System
pump
12345678
Auto
Stage
1 2
Perm. Heat Demand
External Heat Demand
Indoor sensor
Zone control
DHW during unoccupied
DHW priority
Rotate
Off
DHW valve
DHW pump
12345678
Auto
Stage
1 2
Perm. Heat Demand
External Heat Demand
Indoor sensor
Zone control
DHW during unoccupied
DHW priority
Rotate
Off
DHW valve
DHW pump
12345678
Auto
Stage
1 2
Perm. Heat Demand
External Heat Demand
Indoor sensor
Zone control
DHW during unoccupied
DHW priority
Rotate
Off
DHW valve
DHW pump
12345678
Auto
Stage
1 2
Perm. Heat Demand
External Heat Demand
Indoor sensor
Zone control
DHW during unoccupied
DHW priority
Rotate
Off
DHW valve
DHW pump
Indoor Sensor 074 function Selector switch = Indoor Sensor
Thecontrolwillmonitortheindoor, outdoor and supply temperatures,shiftingtheHeatingCurve(and
the WWSD point) up or down to fine adjust the system supply water temperature whenever the room
temperatureisdifferentthanthesettingoftheOccupieddial. IntheUnoccupiedmode,the "Unoccupied"
lightwillcomeon,andthecontrolwillmaintaintheroomatthetemperatureoftheUnoccupieddialsetting.
Unoccupied mode
Connect (short circuit) terminals Com Sen — UnO Sw (17 and 18) together.
The Occupied dial becomes inactive. The Unoccupied dial becomes active
2K RTU function Selector switch = Indoor Sensor
Thecontrolwillmonitortheindoor,outdoor andsupplytemperatures,and shifttheHeatingCurve (and
the WWSD point) up or down to fine adjust the system supply water temperature whenever the room
temperature is different than the setting of the RTU dial. The Occupied and Unoccupied dials are not
functional, and a setback RTU must be used if Unoccupied schedules are desired.
12345678
Auto
Stage
1 2
Perm. Heat Demand
External Heat Demand
Indoor sensor
Zone control
DHW during unoccupied
DHW priority
Rotate
Off
DHW valve
DHW pump
16
DHW
Sen
Out
Sen
2221
Sup
Sen
20
Com
Sen
19
10K
Sen
15
2K
RTU
17
Com
Sen
18
UnO
Sw
Selector switch = Perm. Heat Demand
OR

Caution
Improper installation and operation of this control could result in damage to equipment and possibly even personal injury. It
is your responsibility to ensure that this control is safely installed according to all applicable codes and standards.
Step One Getting ready
Check the contents of this package. If any of the contents listed are missing or damaged, please refer to the Limited Warranty and
Product Return Procedure on the back of this brochure and contact your wholesaler or tekmar sales agent for assistance.
Type 252 includes: • One Control 252 • One Outdoor Sensor 070 • One Universal Sensor 071
• One Data Brochure D 252 • One Data Brochure D 001 • One Application Brochure A 252
Other information available: • Essay E 001 • Essay E 002
Read Application Brochure A 252 and select the correct Application for your job.
Note:
Carefullyreadthe detailsoftheApplication,andthe SequenceofOperationsectionsinall applicablebrochurestoensurethatyouhave
chosen the proper control, and you understand its functions within the operational requirements of your system.
DHW Operation
DHW mode using DHW Sensor 071
•A DHW Sensor 071 must be installed in terminals DHW Sen — Com Sen (16 and 17).
•The DHW Sensor causes the control to monitor the DHW tank temperature. The control generates a DHW demand when 5
minutes has elapsed from the last DHW operation and the tank temperature is dropping quickly, or over a longer period of time
when the tank temperature becomes cooler than the DHW dial setting. This DHW demand causes the control to maintain the
supply water temperature at the DHW dial setting + 20°F(11°C), and over time will increase the supply temperature to the DHW
dial setting + 40°F(22°C).
4
Heating Operation (cont.) — Outdoor temperature cold enough to require heating
With boiler minimum setting higher than heating curve requirement
The "Minimum" light will come on and the control will switch on the boiler(s). The boiler(s) will
fireuntilthesupplytemperaturereachestheminimumsettingplusthedifferentialsetting. When
this point is reached, the "Minimum" light will stay on and the control will cycle the boiler(s) to
maintain the supply water above the Minimum setting.
Outdoor temperature cold enough for heating curve operation
The"Stage" light(s) will come on and thecontrol will fire theboiler(s). The boiler(s) will fire until
the supply temperature reaches the heating curve desired temperature plus one half the dif-
ferential setting, where the "Stage" light(s) will turn off and the boiler(s) will be shut off.
Note: Whenever the boiler(s) are turned off, the control will keep them off until at least the
minimum time delay has expired (1 minute to 5 minutes depending on degree of error).
DHW mode using external DHW Aquastat (no DHW Sensor)
•A 24Vac DHW Demand signal must be applied to terminals DHW Dem — DHW Dem (3 and 4).
•TheDHWDemandsignalcausesthecontroltomaintainasupplywatertemperatureattheDHWdial setting,
and over time can increase the supply temperature to the DHW dial setting + 20°F(11°C) .
DHW operation when control is not in heating mode
When there is a DHW demand, the "DHW Demand" light will come on and the control will operate the DHW
pump or System pump and DHW valve to generate DHW. The boiler(s) will be cycled to maintain the
temperature required by the DHW dial setting (above). When DHW demand is removed, the boiler(s) are
turned off but the pump continues to run for 1 minute to purge the remaining heat from the boiler(s).
DHW operation when control is in heating mode
When a DHW demand occurs, the "DHW Demand" light will come on and the control will operate the DHW
pumporSystempumpandDHWvalvetogenerateDHW.Thecontrolwillcomparetheheatingcurvedesired
supply temperature against the DHW desired supply temperature and operate the boiler(s) to maintain the
supply at whichever is the hotter desired temperature.
DHW during unoccupied selector switch #4 = On
When in Unoccupied mode, the control will operate (as above), to generate DHW.
No DHW during unoccupied selector switch #4 = Off
DHW will not be generated in Unoccupied mode, even with a DHW Demand signal.
1234
Dem DemDemDem
Heat DHW
12345678
Auto
Stage
1 2
Perm. Heat Demand
External Heat Demand
Indoor sensor
Zone control
DHW during unoccupied
DHW priority
Rotate
Off
DHW valve
DHW pump
Installation
15
2K
RTU
19 20
10K
Sen Com
Sen
21 22
Sup
Sen Out
Sen
18
UnO
Sen
16
DHW
Sen
17
Com
Sen
Power
Heat
Demand
DHW
Demand
WWSD
Stage 1 Stage 2
UnOcc.
Minimum
DHW
pump
System
pump
Power
Heat
Demand
DHW
Demand
WWSD
Stage 1 Stage 2
UnOcc.
Minimum
DHW
pump
System
pump
Power
Heat
Demand
DHW
Demand
WWSD
Stage 1 Stage 2
UnOcc.
Minimum
DHW
pump
System
pump
Power
Heat
Demand
DHW
Demand
WWSD
Stage 1 Stage 2
UnOcc.
Minimum
DHW
pump
System
pump
Power
Heat
Demand
DHW
Demand
WWSD
Stage 1 Stage 2
UnOcc.
Minimum
DHW
pump
System
pump
Power
Heat
Demand
DHW
Demand
WWSD
Stage 1 Stage 2
UnOcc.
Minimum
DHW
pump
System
pump

Sensor and unpowered input connections
Power should never be applied to these terminals. Damage to the control will result.
Connect the two wires from the Outdoor Sensor 070 to terminals Com Sen — Out Sen
(20 and 22).
Connect the two wires from the Universal Sensor 071 to terminals Com Sen — Sup Sen
(20 and 21).
Step Two Mounting the base
The control should be removed from its base by pressing down on the release clip in the wiring chamber and sliding upwards on the
control. The base is then mounted in accordance with the instructions in the Data Brochure D 001.
Step Three Rough-in Wiring
All electrical wiring terminates in the control base wiring chamber. It has standard 7/8" (22mm) knock-outs that will accept common
wiring hardware and conduit fittings. Before breaking out the knock-outs, check the wiring diagram and select those sections of the
chamber with common voltages, since the safety dividers will later prevent wiring from crossing between sections. Standard 18 to
22 AWG solid wire is recommended for all low voltage wiring to tekmar controls. Heavier guage wire may not fit properly into the
terminal plugs, while lighter guage wire is too fragile and may also contribute too much resistance to the circuit.
Power should not be applied to any of the wires, during this rough-in wiring stage.
•Install the Outdoor Sensor 070, and the Universal Sensor 071 according to the instructions in the Data Brochure D 001 and run the
wiring back to the control. Options: A DHW Sensor 071 can be connected. An Indoor Sensor 074, RTU or tekmar Zone Control can
also be connected (all purchased separately) . See individual sensor instructions.
•Install the wiring from the other system components; Boiler(s), Pump relays, Heat Demand circuit, etc., to the base.
•Install a 24Vac Class II transformer with a minimum 12VA rating close to the control, and run the wiring from the transformer to the
base. A Class II transformer must be used. Do not connect any of the transformer terminals to ground, as damage to the control
may result.
5
Maximum 24 Volts
Step Four Electrical connection to the control
Power and output connections
The installer should test to confirm that no voltage is present at any of the wires.
• Install the control into the base, sliding it down until it snaps into place.
• All electrical connections are made directly to the terminal plugs.
• Connect the 24Vac power supply from the secondary side of a 24Vac class II transformer to
terminals
C — R (5 and 6). Do not connect either of the transformer terminals to ground.
Connect the System Pump circuit to terminals System Pmp (7 and 8). These terminals lead to a dry
relay contact which closes when the control requires System Pump operation.
If a DHW pump or valve is to be operated by the control, connect its circuit to terminals DHW Pmp (9
and10). Theseterminalsleadtoadryrelaycontact whichcloseswhenthecontrolrequiresDHW pump
/ valve operation.
Note: The252isapprovedforlowvoltageonly(maximum24Vac). Linevoltagestothe pump(s)
must be switched through isolation relay(s).
Connect the boiler circuit(s) to terminals Stage 1 (11 and 12) and Stage 2 (13 and 14). Each set of
terminals lead to a dry relay contact which closes when the control requires boiler operation. Boilers
with a 24Vac control circuit can be switched directly through the control. If higher voltages are used,
isolation relays must be installed.
Powered input connections
If a 24Vac external Heat Demand signal is used, (zone valve end switches, etc.) connect the wiring
fromtheHeatDemandcircuit to terminals HeatDem—HeatDem (1and2). When24Vacis applied
to these terminals, the control will recognize a "call for heat" from the system.
If no DHW Sensor is installed, but a 24Vac DHW Demand signal from an aquastat is used,
connect
thewiringfromtheDHWDemandcircuittoterminals DHWDem—DHWDem (3and 4). When24Vac
isappliedtotheseterminals,thecontrolwillrecognizea"callforDomesticHotWater"andswitchinto
DHW mode.
910
PmpPmp
DHW
65
C R
Power 78
PmpPmp
System
65
C R
Power 78
PmpPmp
System 910
PmpPmp
DHW
1234
Dem DemDemDem
Heat DHW
1234
Dem DemDemDem
Heat DHW
910
78
PmpPmp PmpPmp
System DHW
65
C R
Power
12 13 1411
1 1 22
Stage Stage
12 13 1411
1 1 22
Stage Stage
18
UnO
Sw
16
DHW
Sen
21
Sup
Sen
19
10K
Sen
15
2K
RTU
17
Com
Sen
20
Com
Sen Out Sen
22
16
DHW
Sen
Out
Sen
2219
10K
Sen
15
2K
RTU
17
Com
Sen
18
UnO
Sw
21
Sup
Sen
20
Com
Sen

Step Five Testing the wiring
Caution
•These tests are to be performed using standard testing practices and
procedures and should only be carried out by a properly trained and
experienced technician.
•Before applying power to the control for testing, each terminal plug must be
unplugged from its header on the control. Pull straight down to unplug.
•A good quality electrical test meter, capable of reading from at least
0 — 200 Volts AC, and at least 0 — 1,000,000 Ohms, is essential to properly
test this control.
Test the sensors
•These tests must be made before turning on the power supply, and with the
terminals unplugged.
•The sensors are to be tested according to the instructions in Brochure D 001.
6
Terminal plug disconnected
from its header on the control
OR
type 252
Do not apply
power here!
Maximum 24 Volts
10A
Safety Divider
910
24
Vac
120
or
240
Vac
External
24Vac
60Hz class II
transformer
Heat Demand
Apply 24Vac signal
when heat requested
from system
System Pump
Relay
closes to turn on
System Pump
OR
2K RTU or
Zone Control
240 (optional)
Outdoor
Sensor
070
Supply
Sensor
071
6785
CR
PmpPmp
1234
Dem DemDemDem
12 13 1411
1
Safety Divider
Boiler Relays
close to
turn on boilers
PmpPmp 122
Stage
Unoccupied
Switch
(optional)
DHW Pump
Relay / valve
closes to turn on
pump / valve
Heat System 15 16 17 18 19
UnO
Sw 10K Sen
2K
RTU Com Sen
20 Sup
Sen
21 Out
Sen
Com
Sen
22
Stage
DHW
DHW
Sensor
(optional)
071
DHW
Sen
DHW
10K Indoor
Sensor 074 or
Zone Control
(optional)
10A 10A 10A
DHW Demand
When DHW
requested and there
is no DHW sensor
Power
Electrical connections to the terminal plugs of the 252 control. Control relays are shown in "power down" condition.
For a detailed wiring schematic of your specific application, refer to
the Application Brochure A 252.
15 16 17 1918 20 21 22
2K
RTU
DHW
Sen
Com
Sen
UnO
Sw
Sup
Sen
Out
Sen
10K
Sen
Com
Sen
Out
Sen
22
15
2K
RTU
18
UnO
Sw
21
Sup
Sen
16
DHW
Sen
17
Com
Sen
19
10K
Sen
20
Com
Sen
Option: DHW Sensor 071 input:
InstalltheDHWsensorinawellinthelowerhalfoftheDHWstoragetank.Connectthetwowires
from a Sensor 071 to terminals DHW Sen — Com Sen (16 and 17).
Option: Indoor temperature feedback sensor: (Choose one option only)
(1) ConnectthetwowiresfromanIndoorSensor074oratekmar 10KZoneControl toterminals
10K Sen — Com Sen (19 and 20).
OR
(2) Connectthetwo wires fromatekmar2KRTU, (305, 307,308,or310)or atekmar240Zone
Control to terminals 2K RTU — Com Sen (15 and 17).
Option: Occupied/Unoccupied switch input:
Connect the two wires from the Occupied/Unoccupied dry contact switch (timer, relay, etc.) to
terminals Com Sen — UnO Sw (17 and 18).
18
UnO
Sw
16
DHW
Sen
21
Sup
Sen
19
10K
Sen
20
Com
Sen Out Sen
2215
2K
RTU
17
Com
Sen
16
DHW
Sen
Out
Sen
2221
Sup
Sen
20
Com
Sen
19
10K
Sen
15
2K
RTU
17
Com
Sen
18
UnO
Sw
Out
Sen
2219
10K
Sen
15
2K
RTU
18
UnO
Sw
21
Sup
Sen
20
Com
Sen
16
DHW
Sen
17
Com
Sen

Step Six Essential control settings
To obtain the best operation from a reset control, it is important to measure the system supply temperature as accurately
as possible. Whenever the control receives a heat demand signal, the system pump must be operated to maintain
continuous water flow past the supply temperature sensor.
For specific application details refer to Application Brochure A 252.
AmoredetailedtechnicaldescriptionoftheeffectofcontrolsettingsonoverallsystemoperationisdescribedinthetekmarEssayE 002.
Test the power supply
Make sure exposed wiring or bare terminals are not in contact with any other wires or grounded surfaces. Turn on the power to the
transformeranduseanACvoltmetertomeasurethevoltagebetweenterminals C—R (5 and 6). 22to26VoltsACshouldbemeasured
at these terminals.
Test the powered inputs
If an external Heat Demand signal is used, power up the Heat Demand circuit and supply a Heat Demand signal to the control. Use
an AC voltmeter to measure the voltage between terminals Heat Dem — Heat Dem (1 and 2). 22 to 26 Volts AC should be
measured at these terminals.
If a DHW Demand signal is used, power up the DHW Demand circuit and supply a DHW Demand signal to the control. Use an AC
voltmetertomeasurethevoltagebetweenterminals DHWDem—DHWDem (3 and 4). 22to26VoltsACshouldbemeasuredatthese
terminals.
IfaSystemPumpcircuit is connected tothe SysPmp—SysPmp (7and8)terminals; make sure power tothecircuitisoffandinstall
a jumper in the terminal plug between terminals 7 and 8. When the circuit is powered-up, the pump should operate. If it does not
comeon, checkthecircuit wiringforerrorsandensurethatitispoweredupandthevoltageiscorrect. Checkthedevicesinthecircuit
(pump,switchingrelay,etc.)forfaults. Ifthepumpoperatesproperlywhenthecircuitis poweredup,disconnectthepowerandremove
the jumper. Repeat this step for the DHW pump / valve circuit.
Make sure power to the Boiler circuit is off and install a jumper in the terminal plug between the Stage 1 (11 and 12) terminals. When
the circuit is powered-up, the boiler should operate. If it does not come on, check the circuit wiring for errors and ensure that it is
powered up and the voltage is correct. Check the devices in the circuit (limits, flow switches, etc.) for faults. If the boiler operates
properly when the circuit is powered up, disconnect the power and remove the jumper. Repeat for Stage 2.
Caution
ThetekmarTwoStageBoiler&DHWControl252isanoperatingcontrolandisnotcertifiedorintended
for use as a safety device. Under no circumstances should safety limit devices be left disconnected
afterinstallationofthiscontrol. Theinstallershallcheckallapplicablecoderequirementsandobtain
necessary inspections to ensure that the installation is in compliance with those requirements.
7
Terminal plug pushed into
its header on the control
Settings
15 16 17 19
18 20 21 22
10K
Sen
Com
Sen
Sup
Sen
DHW
Sen
UnO
Sw
Com
Sen
Out
Sen
2K
RTU
Connect the control
Turn the power off and make sure all test jumpers have been removed from the
plugs.
Connecttheplugstothecontrolbycarefullyaligningthemwiththeirrespectiveheaders
and pushing them upwards into the headers. The plugs should snap firmly into place.
The control is now ready for set-up and operation.
Heat Demand switch
When the heating system uses zone valve end switches or some other means of delivering an
external heat demand signal to terminals Heat Dem — Heat Dem (1 and 2), set this selector switch
to "External (1 & 2)" and the control will be enabled when it receives a 24Vac signal from the heat
demand circuit. If an external heat demand signal is not used, set the switch to "Permanent".
Stage 1 & 2 Auto or Off switch
When a Stage switch is set to "Auto", that stage becomes active and its boiler is available. If the
Stage switch is "Off", the control will ignore that stage and not turn it on.
Rotate switch
When set to "Rotate", the firing order of the boilers will change whenever one stage accumulates
48 hrs more running time than the other. When set to "Off", Stage 1 is always the lead boiler.
12345678
Auto
Stage
1 2
Perm. Heat Demand
External Heat Demand
Indoor sensor
Zone control
DHW during unoccupied
DHW priority
Rotate
Off
DHW valve
DHW pump
12345678
Auto
Stage
1 2
Perm. Heat Demand
External Heat Demand
Indoor sensor
Zone control
DHW during unoccupied
DHW priority
Rotate
Off
DHW valve
DHW pump
12345678
Auto
Stage
1 2
Perm. Heat Demand
External Heat Demand
Indoor sensor
Zone control
DHW during unoccupied
DHW priority
Rotate
Off
DHW valve
DHW pump

Heating Curve =
For example: • design outdoor temperature = 5°F (-15°C)
• room temperature = 70°F (21°C)
• design supply temperature = 160°F (71°C)
Heating Curve = = = 1.4
8
Heating Curve
As outdoor temperatures drop, heat losses from a space become
greater and the heating system supply water temperature must be
raisedtomaintainaconstantroomtemperature. Theheatingcurve
valuedescribeshowmanydegreesthesupplywatertemperatureis
raised for a one degree drop in outdoor temperature. The supply
temperature starts to increase when the outdoor temperature falls
belowtheWWSDpoint. Tocalculatethecorrectsettingfor the Heating
Curve, use the following formula.
design supply temperature – room temperature
room temperature – design outdoor temperature
0.4
2.0
3.6
Heating Curve
Outdoor air temperature
Supply water temperature
50
(10) 30 (-1) 10 (-12) -10°F (-23)°C
110
(43)
70
(21)
70
(21)
90
(32)
210
(99)
170
(77)
150
(65)
130
(54)
190
(88)
3.6 3.0 2.4 2.0 1.6
0.8
0.4
1.0
0.6
90
(32)
50°F
(10)°C
Heating
Curve
WWSD
Point
1.2
160°F - 70°F
70°F - 5°F90°F
65°F
For more information regarding the Heating Curve, refer to page 2 of this brochure. If the actual designed supply water temperature
for a system is unknown, a trial setting can be calculated using these typical supply temperatures:
• Fan coils …180°to 210°F (82°to 99°C) • Baseboards …160°to 190°F (71°to 88°C) • Radiant floors …100°to 130°F (38°to 54°C).
Occupied temperature
Whenthereisnoroomtemperaturefeedbacktothecontrol,theOccupieddialsettingdeterminesthestarting
point of the heating curve (WWSD point) and the Heating Curve setting will reset the water temperature as
described in the Heating Curve instructions above.
WhenanIndoorSensor074isconnectedtothecontrol,theOccupieddialsettingbecomestheactual controlled
temperature of the room. This feature will help the control compensate for an incorrectly set heating curve
or for unexpected internal heat gains or losses. If the room temperature is too high or too low, the indoor
sensor allows the heating curve to be shifted up or down accordingly.
When a tekmar Zone Control or 2K RTU (Room Temperature Unit) is connected to the control, the RTU
setting becomes the controlled temperature and the Occupied dial becomes inactive.
Unoccupied temperature
The Unoccupied dial operates in the same way as the Occupied dial.
When the terminals Com Sen — UnO Sw (17 and 18) are shorted out, the control switches from operating
at the Occupied dial setting to operating at the Unoccupied dial setting. When a tekmar Zone Control or 2K
RTU(RoomTemperatureUnit)isconnectedtothecontrol,theRTUsettingbecomesthecontrolled temperature
and the Unoccupied dial becomes inactive.
Zone Control/Indoor Sensor switch
Whenthis selector switch is in the "IndoorSensor" position, and atekmar Indoor Sensor 074 or a tekmar2K
RTU is connected, the control receives room temperature feedback from the RTU or Indoor Sensor and the
Occupied/Unoccupied dials operate as described above.
Whentheswitchisinthe"ZoneControl"position,andatekmarZoneControlisconnected,thecontrol receives
informationfromtheZoneControlthatallowstheheatingcurvetobeshiftedsothesupplywatertemperature
is hot enough to satisfy the requirements of the zone with the highest heat demand.
DHW
When the control receives a DHW Demand signal from either a DHW Sensor or from 24V applied to the
DHW Dem terminals, the control will operate in the DHW mode. See DHW operation, pg. 4
DHW during Unoccupied mode
When this selector switch is in the "On" position, DHW will continue to be generated when the control is
switched into the Unoccupied mode and a DHW Demand signal is received. When the switch is in the "Off"
position,theDHWmodebecomesinactivewhenthecontrolisinUnoccupiedmodeandthecontrolwillignore
any DHW Demand signal.
DHW Priority switch
Whenthisselectorswitchisinthe"On"position,DHWgenerationwillbegivenpriorityoverheatingoperation
when a DHW Demand signal is received. When the switch is in the "Off" position, DHW generation is
simultaneous with heating operation. See Application Brochure A 252.
DHW Valve/Pump switch
Set this selector switch to the "Valve" position when a valve is used in DHW generation and the "Pump"
position when using a pump. See Application Brochure A 252.
Occupied
35
(2) 105 (41)
70°F
(21°C)
140°F
80 200
DHW
35
(2) 105 (41)
70°F
(21°C)
Unoccupied
12345678
Auto
Stage
1 2
Perm. Heat Demand
External Heat Demand
Indoor sensor
Zone control
DHW during unoccupied
DHW priority
Rotate
Off
DHW valve
DHW pump
12345678
Auto
Stage
1 2
Perm. Heat Demand
External Heat Demand
Indoor sensor
Zone control
DHW during unoccupied
DHW priority
Rotate
Off
DHW valve
DHW pump
12345678
Auto
Stage
1 2
Perm. Heat Demand
External Heat Demand
Indoor sensor
Zone control
DHW during unoccupied
DHW priority
Rotate
Off
DHW valve
DHW pump

9
Boiler Differential
TheBoiler Differential adjustment setshowmuch the actual
supply water temperature may deviate from the desired
temperature before stages are turned on or off, and is
determined by the flow rate past the supply sensor relative
to the amount of heat produced by each stage. To prevent
shortoperatingcyclesoftheboiler(s)thecontrolhasadelay
of at least 1 minute between firing cycles. On an installation
where flow rates are known, the Boiler Differential can be
calculated as follows:
Outdoor air temperature
Supply water temperature
50
(10) 30 (-1) 10 (-12) -10°F (-23)°C
110
(43)
70
(21)
70
(21)
90
(32)
210
(99)
170
(77)
150
(65)
130
(54)
190
(88)
3.6 3.0 2.4 2.0
0.8
0.4
1.0
0.6
90
(32)
50°F
(10)°C
Heating
Curve
1.2
Minimum Supply
Setting 130°F
WWSD
Point
70°F
1.6
120°F
Off 170
Minimum
Supply
80
Minimum Supply Temperature
This dial should be set according to the requirements specified by the
boiler manufacturer. Many boilers require a minimum operating
temperature to prevent corrosion from flue gas condensation. The
controlraisesthesupplytemperaturetotheMinimumsettingwhenthe
outdoortemperature drops belowthe WWSD point,and holds itthere
untilthe outdoor temperaturebecomes cold enough to require opera-
tion on the heating curve. When an Indoor Sensor 074 or 2K RTU is
installedina room and the selectorswitchset for "Indoor Sensor", the
controlwill cycletheboiler onandoffattheMinimumSupplytempera-
ture to prevent overheating of the room.
Typical Minimum Boiler Operating Temperatures: • Steel Tube
Boilers …140°to 180°F (60°to 82°C) • Cast Iron Boilers …130°to
150°F (54°to 66°C) • Copper Tube Boilers …105°to 150°F (41°to
66°C) • Condensing or Electric Boilers …Off
100,000 Btu/hr
20 US GPM x 500
Btu/hr
US GPM x 500
Boiler Differential =
For example: = 10°F (6°C)
All boilers will eventually turn on when the temperature falls 5°F (3°C) below the desired
temperature. Delays of 1 to 5 minutes for staging on depend on the degree of control error.
All boilers eventually turn off when the temperature rises 5°F (3°C) above the desired
temperature. Delays of 8 seconds to 3 minutes for staging off depend on the degree of
control error. Within the differential range, no boilers are staged on or off.
Trial setting = 22°F if
flow rates are unknown
22°F
242
Boiler
Differential
Test button
The control can be made to cycle through a test routine whenever the Test button is pushed. The test can
be halted at certain times by pushing the button a second time. For details of the test routine, refer to the
description starting on page 10.
Test
Indicator lights
There are eleven LEDs on the front of the control that will aid in testing and troubleshooting. During normal operation, these lights
indicate the following functions:
Power light on • the 24Vac power supply has been connected and the control is energized.
Heat Demand light on • the control is receiving a 24Vac external Heat Demand signal at terminals Heat Dem — Heat
Dem (1 and 2) or the Heat Demand selector switch is in the "Permanent" position or a 10K Zone
Control causes a Heat Demand.
DHW Demand light on • the control is receiving a 24Vac DHW Demand signal at terminals DHW Dem — DHW Dem
(3and 4) or a DHW sensor is connected and has determined a need for DHW generation.
WWSD light on • theoutdoortemperatureisabovetheWWSDpointandthecontrolhasshuttheheatingsystem off.
Unoccupied light on • the terminals Com Sen — Uno Sw (17 and 18) are shorted together, switching the control into
Unoccupied (setback) mode.
Minimum light on • the control has calculated that it must operate the boiler(s) to maintain the Minimum Supply
temperature since the outdoor temperature is not cold enough for Heating Curve operation.
System pump light on • the system pump relay is on, closing the contacts between terminals 7 & 8.
DHW pump light on • the DHW pump/valve relay is on, closing the contacts between terminals 9 & 10.
Stage 1 or 2 light on • a boiler relay is on, closing the contacts between terminals 11 & 12 or 13 & 14.
Test light on / flashing • the control is going through the programmed test routine / is halted.
Desired temperature
this example
160°F(71°C)
Temperature WarmerCooler
Time
Differential
this example
10°F(5°C)
165°F(74°C)
155°F(68°C)
Temperaturefall
Staging
OFF ON
Temperaturerise

Note;
Whenever the control exits the test routine, there is an automatic 4 second delay before the control can be made to re-enter the test
routine. Pushing the Test button during this 4 second period will have no effect on the control.
Power light on — Test light off
The controlhasexitedthetestroutine,enteredtheoperatingmodeandwillfunctionaccordingtothesequenceofoperationdescribed
on pages 3 and 4. One or more of the other indicator lights may also be on. Refer to pages 3 and 4 for a description of the indicator
lights under operating conditions.
10
Step Seven Operational test of control functions - Test button
The Two Stage Boiler & DHW Control 252 has a Test button which can be used to test all of the main control functions at any time.
When the control is initially powered-up, or when the Test button is pushed, the control automatically runs through the following test
procedure. Ifafaultisdetected,someoftheindicatorlightswillflashanErrorMessage. TheseErrorMessagesarelistedonpage 11.
All red lights on
On power-up, and at the start of each test routine, all of the red status lights are switched on for approximately
5 seconds. During this time the control searches for sensor faults and, if no faults are found, proceeds to the
next step. If a sensor fault exists, the control exits the test routine and indicates the fault by flashing some of
the lights in an error message. These Error Messages are listed on page 11.
Power light on - Test light on - System Pump light on
ThecontrolturnsontheSystempumpfor10secondsand: (a)— proceedstothenextstep, OR (b) —During
the10seconds, ifthereisaHeatDemandsignalandtheTestbuttonispressed, thetestroutinewillbehalted,
the"Test"lightwillflash,andthecontrolwillbeheldinapausemodeforupto5minutes. Duringthe5minutes,
the System pump will remain on. After the 5 minutes, the control will automatically exit the test routine and
enters the normal operating mode. If there is no Heat Demand, the control will not allow a pause and will
proceed to the next step of the test routine. Pushing the Test button during the 5 minute pause will allow the
control to proceed to the next step of the test routine immediately.
Power light on - Test light on - DHW Pump light on
The control turns on the DHW pump for 10 seconds and: (a) — cycles to the next step, OR (b) — During the
10 seconds, if there is a DHW Demand signal, and the Test button is pressed, the test routine will be halted,
the"Test"lightwillflash,andthecontrolwillbeheldinapausemodeforupto5minutes. Duringthe5minutes,
theDHWpumpwillremainon. Afterthe5minutes,thecontrolwillautomaticallyexitthetestroutineandenters
the normal operating mode. If there is no DHW Demand, the control will not allow a pause and will proceed
to the next step of the test routine. Pushing the Test button during the 5 minute pause will allow the control
to proceed to the next step of the test routine immediately.
Testing the Control Functions
Test
Power
Heat
Demand
DHW
Demand
WWSD
Stage 1 Stage 2
UnOcc.
Minimum
DHW
pump
System
pump
Test
Power
Heat
Demand
DHW
Demand
WWSD
Stage 1 Stage 2
UnOcc.
Minimum
DHW
pump
System
pump
Test
Power
Heat
Demand
DHW
Demand
WWSD
Stage 1 Stage 2
UnOcc.
Minimum
DHW
pump
System
pump
Power light on — Test light on — Stage 1 light on
IfthereisaHeatDemandthesystempumpwillbeturnedonorifthereisaDHWDemandtheDHW
pump will be turned on; the control turns on stage 1 for 10 seconds and: (a) — cycles to the next
step, OR (b) — During the 10 seconds, if there is a Heat Demand or DHW Demand signal, and
theTest buttonis pressed, the test routinewill be halted,the "Test" lightwill flash, andthe control
willbe held in apausemode for up to5minutes. During the 5 minutes,the pump and Stage 1will
remain on. After the 5 minutes, the control will automatically exit the test routine and enters the
normal operating mode. If there is no Heat Demand or DHW Demand, the control will not allow
a pause and will proceed to the next step of the test routine. Pushing the Test button during the
5 minute pause will allow the control to proceed to the next step of the test routine immediately.
Power light on — Test light on — Stage 1 light on — Stage 2 light on
The control leaves Stage 1 on, turns on Stage 2 for 10 seconds and: (a) — proceeds to the next
step, OR (b) — During the 10 seconds, if there is a Heat Demand or DHW Demand signal, and
theTest buttonis pressed, the test routinewill be halted,the "Test" lightwill flash, andthe control
will be held in a pause mode for up to 5 minutes. During the 5 minutes, the pump and Stage 1 &
2 will remain on. After the 5 minutes, the control will automatically exit the test routine and enters
thenormaloperatingmode. IfthereisnoHeatDemandorDHWDemand,thecontrolwillnotallow
apauseandwillexitthetestroutine,enteringthenormaloperatingmode. PushingtheTestbutton
during the 5 minute pause will allow the control to exit the test routine immediately.
Heat Demand
and/or DHW
Demand lights
may also be on.
If the Heat
demand light is
on, the System
Pump and
System Pump
light will remain
on. If the DHW
demand light is
on, the DHW
Pump and DHW
Pump light will
remain on.
Test
Power
Heat
Demand
DHW
Demand
WWSD
Stage 1 Stage 2
UnOcc.
Minimum
DHW
pump
System
pump
Test
Power
Heat
Demand
DHW
Demand
WWSD
Stage 1 Stage 2
UnOcc.
Minimum
DHW
pump
System
pump

Whenever a fault is detected in any of the sensors, the indicator lights will flash in specific ways to indicate the problem.
The following look-up table describes each error condition and shows the flashing light sequence that results.
After repairing the problem, press the test button to cycle the control through the test routine and confirm that the fault has been
repaired and that correct control action has been restored.
For detailed Sensor testing instructions see Data Brochure D 001.
Light on continually Light flashing Light off
Step Eight Troubleshooting
Asinanytroubleshootingprocedure,itisimportanttoisolateaproblemasmuchaspossiblebeforeproceeding. TheErrorMessages
and the Test button greatly simplify troubleshooting of the 252.
If a fault occurs during operating mode or during the test routine and the control is flashing an Error Message, identify the fault from
the look-up table at the bottom of this page and then follow standard testing procedures to confirm the problem.
If you suspect a wiring fault, return to steps four and five and carefully check all external wiring and wiring connections.
Notes:
IftheOutdoorSensordevelopseitherashortcircuitoranopencircuit,thecontrolisprogrammedtocalculatetheoutdoortemperature
at -8°F (-22°C) and control the supply temperature accordingly.
The control is programmed to shut the boiler(s) down before the supply temperature can reach a maximum allowable supply water
temperature of 248°F (120°C).
If the Supply Sensor develops either a short circuit or an open circuit, the control is programmed to shut down the boiler(s) and run
the System Pump to prevent overheating.
IfthereisanuninterruptedDHWDemandfor8hoursandtheoutdoortemperatureisbelow34°F(2°C)anerrormessagewillbegiven.
Thecontrolwill operate in the heatingmodeand any DHW Demand is ignored. Toremovethe error message after theDHWsystem
fault has been corrected, the control must be powered down.
If an Indoor Sensor or RTU input becomes shorted out, the Occupied and Unoccupied dial settings will become active.
Afteranyrepairhasbeencompleted,presstheTestbuttontoallowthecontroltocyclethroughthetestroutine. Thiswillallow
you to confirm that correct operation has been restored.
Step Nine Before you leave
Install the wiring cover over the wiring chamber and secure it to the base with the two screws provided. Place the front cover on the
control to cover the setting dials and snap it into place. Install a lock if security is required.
Place this brochure, and all other brochures relating to the installation, in the protective plastic bag supplied with the control. Place
the bag in a conspicuous location near the control for future reference.
It is important to explain the operation and maintainance of this control and of the system to the end user and anyone else who may
be operating the system.
11
10K
Indoor
Sensor
short
circuit
Power
Heat
Demand
DHW
Demand
WWSD
Stage 1 Stage 2
UnOcc.
Minimum
DHW
pump
System
pump
Power
Heat
Demand
DHW
Demand
WWSD
Stage 1 Stage 2
UnOcc.
Minimum
DHW
pump
System
pump
Supply
Sensor
short
circuit
(see
trouble-
shooting
notes)
Power
Heat
Demand
DHW
Demand
WWSD
Stage 1 Stage 2
UnOcc.
Minimum
DHW
pump
System
pump
Outdoor
Sensor
short
circuit
(see
trouble-
shooting
notes)
DHW
Sensor
short
circuit
(see
trouble-
shooting
notes)
Power
Heat
Demand
DHW
Demand
WWSD
Stage 1 Stage 2
UnOcc.
Minimum
DHW
pump
System
pump
Power
Heat
Demand
DHW
Demand
WWSD
Stage 1 Stage 2
UnOcc.
Minimum
DHW
pump
System
pump
Power
Heat
Demand
DHW
Demand
WWSD
Stage 1 Stage 2
UnOcc.
Minimum
DHW
pump
System
pump
Power
Heat
Demand
DHW
Demand
WWSD
Stage 1 Stage 2
UnOcc.
Minimum
DHW
pump
System
pump
Power
Heat
Demand
DHW
Demand
WWSD
Stage 1 Stage 2
UnOcc.
Minimum
DHW
pump
System
pump
Outdoor
Sensor
open
circuit
(see
trouble-
shooting
notes)
Supply
Sensor
open
circuit
(see
trouble-
shooting
notes)
2K
RTU
short
circuit
DHW System
Fault occurs
with 8 Hrs. of
continuous
DHW demand
when Outdoor
temp is less
than 34°F.
(see trouble-
shooting
notes)
Error Messages
Some or all of the yellow output LEDs may also
be on depending on the cause of the error.
(see troubleshooting notes)

Technical Specifications
Dimension (h x w x d) — 6-5/8" x 7-9/16" x 2-13/16" (170 x 193 x 72mm)
Weight — 2.9 lbs (1.3 Kg)
Ambient — 30 to 120°F (0 to 50°C), < 95% RH non-condensing
Power supply — 24Vac ±10%, 60Hz, 3VA class II
Relay capacity — SPST, 24Vac, 10 Amps
Sensors — Sensor 071, Outdoor Sensor 070. Accurate with up to 500 feet (150m) 18AWG cable
Control accuracy —±1°F (±0.5°C)
ThiselectroniccontroldoesnotexceedtheClassBlimitsfor radio noise emissions from digital apparatus as set out in the Radio Interference Regulations of the Canadian
Department of Communications. Le présent numérique n'émete pas de bruits radioeléctriques dépassant les limites applicables aux appareils numériques de Classe B
prescrites dans le réglement sur le brouillace radioeléctrique édicté par le Ministére des Communications du Canada.
Features
11 Indicator lights — Power, Heat Demand, DHW Demand, WWSD, Unoccupied, Min. Supply, System Pump, DHW Pump, Stage 1, Stage 2, Test
System pump output — Isolated SPST relay contacts close when heating is required
DHW pump output — Isolated SPST relay contacts close on DHW Demand
Stage 1 & 2 output — Isolated SPST relay contacts close to operate each stage
Test button — Initiates and controls pre-programmed test run
Error message display — Sensor faults are indicated by flashing light codes
Settings
Heating Curve — 0.4 to 3.6
DHW temperature — 80 to 200°F (27 to 93°C)
Minimum Supply — Off, 80 to 170°F (Off, 27 to 77°C)
Boiler Differential — 2 to 42°F (1 to 23°C)
Occupied — 35 to 105°F (2 to 41°C)
Unoccupied — 35 to 105°F (2 to 41°C)
Stage 1 switch — To switch Stage 1 off or into operating mode
Stage 2 switch — To switch Stage 2 off or into operating mode
Rotate switch — To allow boilers to rotate firing sequence based on hours of use
DHW Unoccupied switch — Generation/No generation of DHW during Unoccupied mode
DHW Priority switch — To make generation of DHW have priority over heating operation
DHW valve/pump switch — Selected for the type of device used when generating DHW
Heat Demand switch — External 24Vac signal or permanent internal signal
Zone Control/Sensor switch — Input from tekmar Zone Control or Indoor Sensor 074
12
In North America: tekmar Control Systems Ltd ., Canada
tekmar Control Systems, Inc., USA
Head office: 4611 - 23rd Street
Vernon, B.C. Canada V1T 4K7
Tel. [phone] Fax. [phone]
All specifications are subject to change without notice.
Printed in Canada on recycled paper.
Product design, software and literature are Copyright © 1992 by:
tekmar Control Systems Ltd. and tekmar Control Systems, Inc.
Technical Data
Printed in Canada on recycled paper by
Wayside Press Ltd. Vernon / Kelowna, B.C.
Limited Warranty: tekmar warrants to the original purchaser each tekmar
product against defects in workmanship and materials when the product is
installed and used in compliance with tekmar's instructions. This limited
warranty covers the cost of parts and labour provided by tekmar to correct
defects in materials and/or workmanship. Returned products that are fully
operational are not considered a warranty case. tekmar also does not cover
parts or labour to remove, transport or reinstall a defective product. tekmar will
not be liable for any damage other than repair or replacement of the defective
part or parts and such repair or replacement shall be deemed to be the sole
remedy from tekmar. This warranty shall not apply to any defects caused or
repairsrequiredas a resultofunreasonable or negligent use,neglect,accident,
improper installation, or unauthorised repair or alterations. In case of defect,
malfunction or failure to conform to warranty, tekmar will, for a warranty period
of24monthsfromthedateofinvoicetotheoriginalpurchaseror12monthsfrom
the date of installation of the product, whichever occurs first, repair, exchange
or give credit for the defective product. Any express or implied warranty which
the purchaser may have, including merchantability and fitness for a particular
purpose, shall not extend beyond 24 months from the date of invoice or 12
months from the date of installation of the product, whichever occurs first.
Replacements: tekmar can send replacement products if requested. All
replacements are invoiced. Any possible credit for the replacement will only be
issued once the replaced product has been returned to tekmar.
Product Return Procedure: Products thatare believedtohave failedmust be
returnedtotekmarControlSystemsLtd.4611-23rdStreet,VernonB.C.Canada
V1T 4K7 when agreed to by tekmar. The installer or other qualified service
person must, at the owner's expense, determine which component has failed.
The product must be returned complete with all of itscomponents (sensors,
base,etc.). Productsmustbereturnedtogetherwiththeproofofpurchasetothe
original purchaser who then returns the product to tekmar after receiving a
Return Goods Authorisation (RGA) number from tekmar.
Pleaseincludethefollowinginformationwiththeproduct: Thefulladdressofthe
original purchaser, the RGA number and a description of the problem.
From the U.S.A., in order to avoid customs charges, products must be returned
viaUSPostwiththepackageclearlymarkedwiththeRGAnumber,producttype
and the statement "Canadian Product returned for repair". For shipping
purposes the product can be valued at one half list price.
1) If returned during the warranty period and the product is defective,
tekmar will issue full credit for the returned product less cost of
missing parts.
2) If returned during the warranty period and the product is fully
operational, tekmar will return the product to the original purchaser
for a testing cost of $30.00 plus postage.
3) If returned during the warranty period and the product is not
damaged and is fully operational, tekmar can take back the
product for a return charge of 40% of the product's net value. This
request has to be specified otherwise the product will be returned
with a testing cost of $30.00 plus postage.
4) If returned after the warranty period and the product needs repair,
tekmar will repair and return the product. Repair and postage
costs will be invoiced. tekmar's repair costs are calculated at
$30.00 / hour plus the cost of parts. If the repair costs will be more
than $60.00 a repair estimate will be sent to the original purchaser.
Limited Warranty and Product Return Procedure