heat-timer Mini-Extension Owner's manual

R
INSTALLATION AND OPERATION INSTRUCTIONS
Mini-MOD & Mini-Extension
SEQUENCING MODULATING CONTROL
FOR HYDRONIC HEATING SYSTEMS
This manual attempted to be complete and accurate at the time of
publication. Additional upgrades and new features may change Mini-
MOD functions. Upgrades to this manual may occur at any time.
Contact the factory for further details.
WARNING
The Mini-Mod is strictly an operating control. It CANNOT be used as a limit control. All boilers must have all
safety and limit controls required by code. It is the responsibility of the installer to verify that all the safety and
limits are working properly before the Mini-Mod is installed.
This control must be installed by a licensed electrician.
Mini-MOD
SYSTEM
A
B
C
D
Full Modulation Sequencing Control
12
RUNPROGRAM
FOR ALL CIRCUITS
120VAC, 6A RESISTIVE
OUTPUT RATINGS:
1A PILOT DUTY, 15A TOTAL
115VAC 60Hz , 30VA MAX
INPUT RATINGS:
USE COPPER WIRE,
DO NOT APPLY ANY VOLTAGE
TO INPUT TERMINALS
345678910 11 12 13 15
14 17
16 18 22
20
19 21 24
23 29
25 27
26 28 32
30 31
LN-+
+
TT
OORS-485
mA
GNDVLT
SYSABCD
PWR CUR/VLT
A
-+
+
mA
GND VLT
-+
+
mA
GND VLT
-+
+
mA
GND VLT
+
mA
TEMP
OUTDOOR
OO
TEMP
SYSTEM
EXTENSION
MODULE
CUR/VLT
B
CUR/VLT
C
CUR/VLT
D
CLASS 1 WIRE ONLY.
------
PROVE
/DHW
SHUTDOWN
/SETBACK
ENCLOSED
ENERGY
MANAGEMENT
EQUIPMENT
LISTED
99RA
CAUTION: RISK OF ELECTRIC SHOCK
More than one disconnect switch may be required
to de-energize the equipment before servicing.
Table of Contents
MINI-MOD LAYOUT . . . . . . . . . . . . . 3
MINI-MOD OVERVIEW . . . . . . . . . . . 4
UNDERSTANDING OPERATION CONCEPT 5
Making Sure You Have the Right Control . 6
INITIAL SETUP . . . . . . . . . . . . . . . 6
Selecting the System Features. . . . . . . 6
INSTALLATION . . . . . . . . . . . . . . . 7
Mounting the Enclosure . . . . . . . . . . 7
Install the Sensors . . . . . . . . . . . . . 8
Wiring. . . . . . . . . . . . . . . . . . . . 9
MENU SEQUENCE . . . . . . . . . . . . . 12
Startup Settings . . . . . . . . . . . . . . 14
Operating Settings . . . . . . . . . . . . . 16
System Settings . . . . . . . . . . . . . . 18
History . . . . . . . . . . . . . . . . . . . 21
Maintenance . . . . . . . . . . . . . . . . 22
Display . . . . . . . . . . . . . . . . . . . 23
Boiler Stage Settings . . . . . . . . . . . . 24
TROUBLESHOOTING. . . . . . . . . . . . 26
APPLICATION DIAGRAMS . . . . . . . . . 28
SPECIFICATIONS . . . . . . . . . . . . . . 32

2 Heat-Timer Corp.
MINI-MOD LAYOUT . . . . . . . . . . . . . 3
MINI-MOD OVERVIEW . . . . . . . . . . . 4
UNDERSTANDING OPERATION CONCEPT 5
Reset Ratio/Outdoor Reset . . . . . . . . . .5
Making Sure You Have the Right Control . 6
INITIAL PILOT PROGRAM . . . . . . . . . 6
Selecting the System Features. . . . . . . 6
INSTALLATION . . . . . . . . . . . . . . . 7
Mounting the Enclosure . . . . . . . . . . 7
Install the Sensors . . . . . . . . . . . . . 8
Heating System Sensor (HSS) Installation. . . 8
Outdoor Sensor Installation . . . . . . . . . . 8
Wiring. . . . . . . . . . . . . . . . . . . . 9
Wiring the Power (Terminals 1, 2) . . . . . . .9
Wiring the Sensors . . . . . . . . . . . . . . .9
Wiring the Shutdown (Terminals 31, 32) . . . . 9
Wiring the Prove (Terminals 29, 30) . . . . . 10
Wiring the Domestic Hot Water Call DHW
(Terminals 29, 30) . . . . . . . . . . . . . . 10
Wiring the System Output (Terminals 3, 4). . 10
Wiring the Boilers . . . . . . . . . . . . . . 10
Wiring to Modulating Motors . . . . . . . . . 11
Connecting to the Mini-Extension Panels . . 11
MENU SEQUENCE . . . . . . . . . . . . . 12
Startup Settings . . . . . . . . . . . . . . 14
Program Change Settings . . . . . . . . . . 14
Startup Sequence . . . . . . . . . . . . . . 14
Sensor Type . . . . . . . . . . . . . . . . . 14
EMS Input Mode (Available in Set point Only)14
Selecting the Output Type . . . . . . . . . . 14
Selecting the Modulating Mode . . . . . . . 15
Prove/Domestic Hot Water (DHW) . . . . . . 15
Setback Mode . . . . . . . . . . . . . . . . 15
Boost Mode . . . . . . . . . . . . . . . . . 15
Sensor Fault . . . . . . . . . . . . . . . . . 15
Operating Settings . . . . . . . . . . . . . 16
Program Change Settings . . . . . . . . . . 16
Season . . . . . . . . . . . . . . . . . . . . 16
Set Point (not Adjustable in EMS Mode) . . . 16
Reset Ratio. . . . . . . . . . . . . . . . . . 16
Outdoor Cutoff Temperature . . . . . . . . . 17
Offset . . . . . . . . . . . . . . . . . . . . . 17
Minimum Water Temp . . . . . . . . . . . . 17
Maximum Water Temp . . . . . . . . . . . . 18
System Settings . . . . . . . . . . . . . . 18
Gain . . . . . . . . . . . . . . . . . . . . . 18
Lead Boiler Rotation . . . . . . . . . . . . . 18
Purge Delay . . . . . . . . . . . . . . . . . 19
Lag Delay . . . . . . . . . . . . . . . . . . 19
Standby Time. . . . . . . . . . . . . . . . . 19
System Run-On . . . . . . . . . . . . . . . 19
Setback. . . . . . . . . . . . . . . . . . . . 20
Last Stage Hold . . . . . . . . . . . . . . . 20
Day/Night Schedules . . . . . . . . . . . . . 21
Set Time . . . . . . . . . . . . . . . . . . . 21
History . . . . . . . . . . . . . . . . . . . 21
Maintenance . . . . . . . . . . . . . . . . 22
System & Outdoor Sensor Trim . . . . . . . 22
Soft-Off Delay . . . . . . . . . . . . . . . . 22
Output Trim. . . . . . . . . . . . . . . . . . 22
Configuration . . . . . . . . . . . . . . . . . 23
Display . . . . . . . . . . . . . . . . . . . 23
Display Boiler Modulation Status. . . . . . . 23
Display Messages . . . . . . . . . . . . . . 23
Boiler Stage Settings . . . . . . . . . . . . 24
Mode . . . . . . . . . . . . . . . . . . . . . 24
Ignition %. . . . . . . . . . . . . . . . . . . 25
Modulation Start % . . . . . . . . . . . . . . 25
Copy Settings - Boiler A Only . . . . . . . . 25
TROUBLESHOOTING. . . . . . . . . . . . 26
APPLICATION DIAGRAMS . . . . . . . . . 28
SPECIFICATIONS . . . . . . . . . . . . . . 32
Contents

Mini-MOD & Mini-Extension Installation Manual 3
Mini-MOD
SYSTEM
A
B
C
D
Full Modulation Sequencing Control
12
RUNPROGRAM
FOR ALL CIRCUITS
120VAC, 6A RESISTIVE
OUTPUT RATINGS:
1A PILOT DUTY, 15A TOTAL
115VAC 60Hz , 12VA MAX
INPUT RATINGS:
USE COPPER CONDUCTORS ONLY
DO NOT APPLY ANY VOLTAGE
TO INPUT TERMINALS
345678910 111213 15
1417
16 18 22
20
19 2124
23 29
25 27
26 28 32
30 31
LN
-+
+
TT
OORS-485
mA
GNDVLT
SYSABCD
PWR
CUR/VLT
A
-+
+
mA
GNDVLT
-+
+
mA
GNDVLT
-+
+
mA
GNDVLT
+
mA
TEMP
OUTDOOR
OO
TEMP
SYSTEM
SHUTDOWN
/SETBACK
EXTENSION
MODULE
CUR / VLT
B
CUR / VLT
C
CUR/VLT
D
ENCLOSED
ENERGY
MANAGEMENT
EQUIPMENT
LISTED
99RA
CAUTION: RISK OF ELECTRIC SHOCK
More than one disconnect switch may be required
to de-energize the equipment before servicing.
PROVE
/DHW
The digital display shows the system status, set point,
lead stage <in brackets>, and status of each stage.
To view and adjust settings, press the appropriate buttons.
120VAC Power
Four N.O. Boiler startup relay
outputs. Each is wired in series
with each boiler's limit circuit.
System Output controls
pumps, valves, or other
system components.
Four modulation outputs can be 0-5V,
0-10V, 1-5V, 2-10V, or 4-20ma. Go to
StartupMenutodeterminethetypeof
output for each stage.
LED indicates the
associated relay status.
Buttons function is presented on
Bottom Row of display.
When connecting Outdoor and System
Sensors, no Polarity is observed.
Prove terminals must be connected
for Mini-Mod to operate boilers.
Connect Extension panels to
add additional stages using
a 6 pin phone line only (cable
provided with Mini-Extension).
Program Switch to restrict access to
function changes. This switch is
covered with Wiring Enclosure.
MINI-MOD LAYOUT

4 Heat-Timer Corp.
MINI-MOD OVERVIEW
SEQUENCES UP TO 4 FULLY MODULATING STAGES.
The Mini-MOD is the perfect control whenever multiple fully modulating stages are required for hydronic heating applications. The
Mini-MOD controls the on/off and the modulation of each stage to maintain precise system set point control.
PID TYPE LOGIC
The Mini-MOD’s control algorithms allow it to look at the rate of change in the system. If the system temperature is changing quickly,
the Mini-MOD will react quickly to adjust the modulating stages’ output. If the system temperature changes slowly, the Mini-MOD will
make slow and gradual output adjustments. Therefore, the Mini-MOD adapts to specific system requirements and minimizes fluctuations
around the set point.
CONTROLS 0-5 V, 0-10 V, 1-5V, 2-10V, OR 4-20 MA MODULATING MOTORS
The Mini-MOD is designed to accurately control the output from 0 to 100% of modulation for each of these different types of motors.
One Mini-MOD can even control a variety of the above different motors.
ONLY ONE SENSOR
When Set Point sensor type is selected, the Mini-MOD requires only one sensor located in the common output header of all stages.
However, when Reset is selected, an additional Outdoor Sensor is required for Outdoor Reset Ratio input.
DIGITAL DISPLAY OF ALL SYSTEM SETTINGS
The Mini-MOD’s alphanumeric digital display names each system parameter in simple English and shows its precise value. The easy
to follow menu system allows users to quickly make changes to any system setting without having to learn any specialized codes or
keyboard commands.
AUTOMATIC ROTATION AMONG STAGES
Rotating the first stage to be activated on a call for output promotes even wear on each stage. The Mini-MOD has three modes of rotation:
Manual, Last On, or Time. The Time rotates the lead stage every selected time period from every hour to every 60 days.
OUTDOOR RESET
The Mini-MOD has a hydronic outdoor temperature reset function. This allows the Mini-MOD to change the set point based on outdoor
temperature. Furthermore, additional settings have been added to fine tune this operation, like Offset, Minimum, and Maximum Water
Temperature and night setback schedule.
STANDBY BOILERS
Each of the Mini-MOD stages can be configured as a Standby boiler with an adjustable Standby delay. A boiler can be used as a backup
during extended large demand periods.
SYSTEM OUTPUT
In Set Point mode, this output can be used to activate a system pump, combustion air damper, or perform any other function that is required
when any stage is active. In Outdoor Reset mode, the System Output will activate whenever the outdoor temperature is below the Outdoor
Cutoff setting. A System Prove input checks the status of components activated by the System output before stages can be activated.
STAGING (NORMAL) OR PARALLEL MODULATION
The Mini-MOD can stage boilers as needed. That will allow it to increase the modulation on the lead boiler. When the lead boiler reaches
its modulation start point adjustment and does not satisfy the load, the Mini-MOD will start the next boiler and so on... Moreover, the
Mini-MOD allows for a parallel mode that can modulate several boilers together as a one large boiler. This mode is useful for boilers
with lower water content, which are usually more efficient at lower firing points.
ADD UP TO 16 BOILER STAGE (OPTIONAL)
As a stand-alone, the Mini-MOD is designed to control four modulating boilers. However, it has the capability of expanding its control
to two extension panels each with six boiler stages. Thus, the Mini-MOD can control a total of up to 16 boiler stages.

Mini-MOD & Mini-Extension Installation Manual 5
UNDERSTANDING OPERATION CONCEPT
The Mini-MOD has multiple operating modes that satisfy most hydronic systems. It can
change the System Set Point based on outdoor temperature (Outdoor Reset) or it can modulate
its stages to achieve an adjustable fixed Set Point.
In Outdoor Reset, the Mini-MOD controls a hot water heating system to provide a building with
comfortable and even heat levels. The Mini-MOD varies the temperature of the circulating
heating water in response to changes in the outdoor temperature. The heating water temperature
is controlled through the modulation of stages.
The Mini-MOD also controls the system circulating pump with an adjustable Outdoor Cutoff.
When the outdoor temperature is above Outdoor Cutoff, the pump is off and no heating water is
circulated through the system. When the outdoor temperature drops below the Outdoor Cutoff,
the system pump relay is activated and the heating water circulates through the system. The
temperature of the heating water is controlled by the Reset Ratio, Water Offset, and changes
with Outdoor temperature.
RESET RATIO/OUTDOOR RESET
When a building is being heated, heat escapes through the walls, doors, and windows to
the colder outside air. The colder the outside temperature, the more heat escapes. If you
can input heat into the building at the same rate that it is lost out of the building, then
the building temperatures will remain constant. The Reset Ratio is an adjustment that
lets you achieve this equilibrium between heat input and heat loss.
The starting point for most systems is the 1.00 (OD):1.00 (SYS) (Outdoor Temperature
: Heating Water Temperature) ratio. This means that for every degree the outdoor
temperature drops, the temperature of the heating water will increase one degree. The
starting point of the curves is adjustable, but comes factory selected at 70°F Outdoor
Temp. and 100°F Water Temp. For example with a 1.00 (OD):1.00 (SYS) ratio, if the
outdoor temperature is 50°F, this means the temperature has fallen 20°from the starting
point of 70°F. Therefore, the heating water temperature will increase 20°to 120°F.
Each building has different heat loss characteristics. A very well insulated building will
not lose much heat to the outside air, and may need a Reset Ratio of 2.00 (OD):1.00
(SYS) (Outdoor:Water). This means the outdoor temperature would have to drop
2 degrees to increase the water temperature 1 degree. On the other hand, a poorly
insulated building with insufficient radiation may need a Reset Ratio of 1.00 (OD):2.00
(SYS). This means that for each degree the outdoor temperature dropped the water
temperature will increase 2 degrees. The Mini-MOD has a full range of Reset Ratios to
match any buildings heat loss characteristics.
A heating curve that relies not only on Outdoor temperature but also on type of radiation
will improve heat comfort. The following are suggested initial settings for different
types of radiation based on average building insulation and heat loss. The contractor
can fine tune these adjustments based on the specific building need.
Type of Radiation in Building Reset Ratio Offset
Radiators (Steel & Cast Iron) 1.00 (OD) : 1.00 (SYS) 0˚F
Baseboard (Finned copper tube& Cast Iron) 1.00 (OD) : 1.00 (SYS) 0˚F
Radiant (High Mass/Concrete) 4.00 (OD) : 1.00 (SYS) -10˚F
Radiant (Low Mass/Joists) 2.00 (OD) : 1.00 (SYS) -10˚F
Fan Coils & Air Handlers 1.00 (OD) : 1.00 (SYS) 20˚F
Outdoor Temperature
Water Temperature
70 405060
130
120
110
100
Outdoor Temperature
Water Temperature
70 405060
110
100
90
80
Outdoor Temperature
Water Temperature
70 405060
150
140
130
120
1:4
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  
    
   
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   
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1:4
1:4 1:1
1:1
1:1
4:1
4:1
4:1
90
100
+20 Offset
-20 Offset
Outdoor Temperature (in °F)
70 60 50 40 20
30 0 -10
10 -20
100
120
110
130
140
150
160
180
170
190
200
210
220
1:3 1:2 1:1.5
1:1.25
1:1
1.25:1
1.5:1
2:1
3:1
4:1
Water Temperature (in °F)
Reset Ratio Curves
    
     
1:4
WARNING
When controlling a non condensing
boiler directly without the use of a
mixing valve, minimum boiler water
temperature must be set to boiler
manufacturer specifications. In that
case, system temperature must not go
below such temperature.

6 Heat-Timer Corp.
MAKE SURE YOU HAVE THE RIGHT CONTROL
If you need the Mini-MOD to do additional tasks that either are not listed or do not know how to configure them, contact Heat-Timer
Corp. Sales Department either by Phone [phone], Fax [phone], or by E-mail [e-mail].
INITIAL SETUP
Setting an Initial Program will ease the configuration of the Mini-MOD and will give the opportunity to utilize many of the energy saving
features and give more comfortable heat when needed.
The program should consist of the following:
• Selecting the features that your system can utilize,
• Installation: Install the Control, switches and sensors,
• Setting the System Startup,
• Setting the System Settings,
• Setting the Stages
• Adjusting Reset Ratio and Water Offset (In Reset Mode Only)
SELECTING THE SYSTEM FEATURES
The Mini-MOD has been designed with Hydronic building heating as the primary purpose. With this in mind, many of the Mini-MOD
features can be utilized to ease, enhance and improve your system performance. Some of these features are listed in this section.
OUTDOOR RESET OR SET POINT
• The Mini-MOD can control the System Temperature either by adjusting the calculated temperature according to the Outdoor
Temperature (Outdoor Reset) or by maintaining an adjustable Set Point. The earlier relies on an Outdoor Sensor (supplied with the
control) and achieves better fuel savings in addition to better comfort.
NUMBER OF STAGES
• The Mini-MOD can be configured to control up to 4 modulating boilers. It can control up to 16 boiler stages using a maximum of
two Mini-MOD Extension Panels
MODULATION MODE
•
The Mini-MOD can stage boilers using one of two methods. Normal Modulation Mode, allows it to increase the modulation of the
lead boiler. When the lead boiler reaches its modulation start point adjustment and does not satisfy the load, the Mini-MOD will
start the next boiler and so on. This mode targets boilers that can run more efficient at higher modulation rates.
• The Parallel Modulation Mode can modulate several boilers together as a one large boiler. This mode is useful for boilers that are
more efficient at lower firing points.
MODULATING SIGNAL
• The Mini-MOD is designed to accurately control the output from 0 to 100% of modulation for each of these different types of motors.
One Mini-MOD can even control a variety of the above different modulation motors.
AUTOMATIC ROTATION AMONG BOILERS
• Rotating the first burner to be activated on a call for output promotes even wear on all burners. The Mini-MOD has three modes of
rotation: Manual, Last-ON, or Time automatically rotating every selected time period from every hour to every 60 days.
STANDBY BOILER
•
Any boiler can be configured as a Standby boiler. It withholds a specific boiler from being included in the Lead Rotation. However,
the Standby boiler will be fired only as a backup when all other stages combined cannot satisfy the demand and after an adjustable
delay period.
SETBACK OR DAY/NIGHT SCHEDULING
Two Setback modes are available for the Mini-MOD:
• The Day/Night Scheduling provides an adjustable time-based schedule for the Setback.
• The Setback mode uses an external signal to switch the operation of the Mini-MOD in and out of setback mode.

Mini-MOD & Mini-Extension Installation Manual 7
System Run-On
• This feature lets the Mini-MOD run the SYS relay for a longer period after the boilers have been turned off. When this relay is used
to control a pump, it helps in dissipating the excess heat from the boilers combustion chamber.
INSTALLATION
Each of the Mini-MOD or Mini-Extension consists of three primary enclosure components.
• The Enclosure Display Module: contains the display, buttons, LEDs and electric wiring terminals. It has two screws to hold
it to the base. A program configuration switch, used to adjust Mini-MOD settings, is placed above the terminals. This switch is
enclosed with the enclosure wiring cover for security. Wiring terminals are of the plug-in type to ease installation and removal.
• The Enclosure Base: contains the holes to mount and hold the control against the wall or any flat surface. All other enclosure
components mount on the base. The bottom section of the Enclosure Base contains the wiring chamber with knockouts on the
bottom to easy installation.
• The Enclosure Wiring Cover: seals the wires from the external environment. It has two screws to hold it the base and a hole to
secure a lock on the wiring enclosure. A plastic web that separates the wiring chamber into high and low volt sections has been
provided.
MOUNTING THE ENCLOSURE
• Select a location near the equipment to be controlled.
• The surface should be flat, and be sufficiently wide and strong to hold the
Mini-MOD or Mini-Extension.
• Keep the control away from extreme heat, cold, or humidity. Ambient
operating temperature is from 20 to 120°F.
• Remove the Enclosure Wiring Cover from the control enclosure by
removing the two bottom screws.
• Remove the Enclosure Display Module by removing the middle screws.
• Screw the Enclosure Base to the surface through the upper and lower
mounting holes on the back of the enclosure.
• Replace the Enclosure Display Module and replace the middle screws.
• Do not replace the enclosure wiring cover until all wiring is done.
 
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   

8 Heat-Timer Corp.
INSTALL THE SENSORS
HEATING SYSTEM SENSOR (HSS) INSTALLATION
LOCATING HSS
• Put the Heating System sensor approximately 10' feet past the last boiler on
the common supply header but before any major takeoffs.
• The sensor must be located where it sees the output of all the boiler stages. If
a boiler is piped so that the sensor does not see its output, the Mini-MOD will
not sequence the boilers correctly.
• Only use a Standard Brass Tube sensor (HT #904015-00 or equivalent).
• The sensor wires can be extended up to 500' using a shielded 2-conductor
cable (Belden #8760 or equivalent). Do not ground the shield at the sensor
but at the panel using one of the terminals marked with an “O”.
• Do not run sensor wires in conduit with line voltage wiring.
IMMERSION HEATING SYSTEM SENSOR (HSS) INSTALLATION
• Install a 3/8"ID 1/2"NPT immersion well (HT #350147-00 or equivalent).
• Insert the sensor probe of the supplied sensor into the well.
STRAP-ON HEATING SYSTEM SENSOR (HSS) INSTALLATION
• Strap the sensor to the pipe using metal clamps. Do not over tighten the
clamp.
• Strap pipe insulation around the sensor and pipe.
Immersion Well
3/8" ID 1/2" NPT
Heating System
Sensor
Common Supply Pipe
Sensor Probe
Immersion Heating System Sensor
Shield
Common Supply Pipe
Sensor Probe
Strap-On Heating System Sensor
Shield
Pipe Insulation
CAUTION
If the HSS can not sense the correct
heating system water temperature being
supplied to the building, the Mini-MOD
will not provide comfortable heat levels.
Be sure the HSS is located on a main
supply pipe which can not easily be
isolated from the system.
OUTDOOR SENSOR INSTALLATION
• Only use the Heat-Timer sensor included with the unit.
• Locate the sensor in the shade on the north side of the building. The sensor
should never be in direct sunlight.
• Be sure the location is away from doors, windows, exhaust fans, vents, or
other possible heat sources.
• The sensor should be mounted approximately 10' feet above ground level.
• Mount the sensor clip base to the outside of the building. Insert the sensor in
the middle and snap close the clip on the sensor.
• The sensor wires can be extended up to 500' using shielded 2-conductor
cable. Do not ground the shield at the sensor but at the panel using one of the
terminals marked with an “O”.
• Do not run sensor wires in conduit with line voltage wiring.
WARNING
The Mini-MOD is an operating control only. All boilers must have all
safety and limit controls required by code. It is the responsibility
of the installer to verify that all the safety and limits are working
properly before the Mini-MOD is installed.
CAUTION
Determining the proper location for the Outdoor Sensor is very
important. The Mini-MOD will base the heat on the outdoor
temperature information it receives from this location. If the sensor
is in the sun, or covered with ice, its reading will be different from the
actual Outdoor temperature (OD).

 
 
 
 

Mini-MOD & Mini-Extension Installation Manual 9
WIRING
WIRING THE POWER (TERMINALS 1, 2)
• Bring the 120VAC 60Hz power wires through the bottom Knockout of the enclosure.
• Class 1 voltages must enter the enclosure through a different opening from any Class 2 voltage wiring.
• Connect the hot line to terminal marked L.
• Connect the neutral line to the terminal marked N.
• Heat-Timer recommends installing a surge suppressor on the power source to the Mini-MOD.
WARNING
Class 1 voltages must enter the enclosure through a different opening from any Class 2 voltage wiring.
Heat-Timer recommends installing a surge suppressor on the power source to the Mini-MOD.
12
LN
PWR
Line
Neutral
120VAC
PowerSource
WARNING
Connect the shield at the control terminal end and cut the shield wire at the sensor end.
29 2527
26283
TT
OO
TEMP
OUTDOOR
O
TEMP
SYSTEM
System Sensor
Sensor Shiled
PROVE
/DHW
WIRING THE SENSORS
SYSTEM SENSOR WIRING (TERMINALS 27, 28)
• A Mini-MOD must be connected to a temperature sensor located in the common header.
• The Mini-MOD is designed to be connected to a HT #904015-00 temperature sensor for immersion in a
3/8ID well (HT #350147-00 or equivalent). Contact the factory for additional temperature sensor options.
• Temperature sensor wires can be extended up to 500’ by splicing shielded 2-
conductor cable (Belden #8760 or equivalent).
• Temperature sensors have no polarity. Connect the two wires from the sensor
to the Mini-MOD terminals marked SYSTEM TEMP 27, 28.
• Connect the sensor shield to the circled terminal 28 with one of the sensor wires.
OUTDOOR SENSOR WIRING (TERMINALS 25, 26)
• When Outdoor Reset is selected, the Mini-MOD will vary the system Set Point based on outdoor temperature.
• Whether in Set Point or Outdoor Reset modes, the outdoor sensor can be used as an Outdoor Cutoff.
The Mini-MOD will disable all Boilers when the outdoor temperature is above the adjustable Outdoor
Cutoff temperature. This feature will automatically be activated when an outdoor sensor is connected.
• For an outdoor sensor use a Heat-Timer outdoor sensor (HT #904015).
• The sensor wires can be extended up to 500’ using shielded 2-conductor cable (Belden #8760 or equivalent).
• Temperature sensors have no polarity. Connect the wires from the outdoor sensor
to the Mini-MOD terminals marked OUTDOOR TEMP - 25, 26.
• Connect the shield to the circled terminal 26 with one of the sensor wires.
29 25 27
26 28
3
TT
OO
TEMP
OUTDOOR
TEMP
SYSTEM
Outdoor Sensor
Sensor Shiled
PROV
/DHW
WIRING THE SHUTDOWN (TERMINALS 31, 32)
• This feature can be used whenever it is desirable to turn off the Mini-MOD stage outputs from a remote
location or another controller (i.e. EMS input).
• When the Shutdown feature is enabled by closing a dry contact, all active boilers will immediately modulate
down to low then off. The lead boiler will remain in low for a Soft-Off period; default setting is 45 seconds,
and then turn off.
• The System Output relay will remain active until the System Delay is over and then it will turn off.
• The Shutdown signal must be a dry contact only. No voltage can be placed across the SHUTDOWN terminals.
• Bring the two wires from the dry contact to the terminals marked SHUTDOWN- 31,32.
29 28 32
30 31
OOO
MP
S
TEM
Shutdown
Signal
PROVE
/DHW
SHUTDOWN
/SETBACK

10 Heat-Timer Corp.
WIRING THE PROVE (TERMINALS 29, 30)
• The Prove feature is provided to check system component operation and must be selected in the Startup Menu.
• A typical use of this feature is to check for flow before firing any boiler.
• If the PROVE input is open on a call, the Mini-MOD will enable only the System Output. All Boiler outputs
will be off when the PROVE input is open.
• A factory-installed jumper provides the System Prove signal. Do not remove the jumper unless it will be
replaced by a System Prove signal or use the terminals for DHW call.
• Bring the two wires from the dry contact to the terminals marked PROVE - 29, 30. No voltage can be placed
across the PROVE terminals
WARNING
The PROVE input can not be used as a safety limit. All equipment must have its own
certified limit and safety controls as required by local codes. If Prove is selected in the
startup menu, no boiler stage will start unless Prove terminals are shorted. DO NOT
remove the PROVE jumper supplied unless replacing it with a Prove signal.
29
27
628 32
30 31
T
O
O
P
O
R
OO
TEMP
SYSTEM
Prove Signal
PROVE
/DHW
SHUTDOWN
/SETBACK
29
27
2
628 32
30 31
T
O
O
P
O
R
OO
TEMP
SYSTEM
DHW Signal
PROVE
/DHW
SHUTDOWN
/SETBACK
WIRING THE DOMESTIC HOT WATER CALL DHW (TERMINALS 29, 30)
• DHW can be used to raise system Set Point to 200°F or Maximum Water temperature, whichever is lower.
DHW with or without Priority must be selected in the Startup Menu.
• DHW Call terminals are dry contact N.O. terminals.
• Wire an aquastat or other controls to provide closure on the DHW Call terminals.
• Remove the jumper on the DHW terminals for proper operation.
WIRING THE SYSTEM OUTPUT (TERMINALS 3, 4)
System Output Operation in Set Point Mode
• The SYS output relay will energize whenever the outdoor temperature drops below the Outdoor Cutoff or
whenever a boiler output is active. If no outdoor sensor is connected and the last boiler relay has de-energized,
the SYS relay will remain energized for a period set by the System Run-On.
• No Boilers will be activated until the prove input is shorted. If a Prove is not required, the factory-installed
jumper should remain connected.
• A typical use of the SYS output is to activate a system pump starter. The pump can run whenever there is a call
for heat. When heat is no longer required, the pump will stay active for an adjustable Pump Run-On delay.
3456
SYS A
SystemPump
orPu
mpStarter
System Output Operation in Reset Mode
• The SYS output relay will energize whenever the outdoor temperature is below the Outdoor Cutoff.
• The SYS will remain constantly energized while the outdoor temperature is below the Outdoor Cutoff.
• When the outdoor temperature rises 2°F above the Outdoor Cutoff, the SYS output will remain energized for
the period set by the System Run-On.
• The SYS output has one Normally Open (N.O.) relay contact.
• The N.O. contacts are dry contacts only. They do not source any voltage.
• Class 1 voltages must enter the enclosure through a different opening from any Class 2 voltage wiring.
• Each N.O. contact is capable of switching 6A resistive at 120VAC.
WIRING THE BOILERS
WIRING THE BOILER OUTPUTS (A TERMINALS 5, 6), (B TERMINALS 7, 8), ...
• Each Boiler output (A through D) has one Normally Open (N.O.) relay contact.
• The N.O. contacts are dry contacts only. They do not source any voltage.
• Each N.O. contact is capable of switching 6A resistive at 120VAC.
• Total output of all Boilers, including the SYS, must not exceed 15A.
• Wire the N.O. relay contacts in series with the unit’s limit circuit.
• Class 1 voltages must enter the enclosure through a different opening from any Class 2 voltage wiring.
5
678910 11
1
ABCD
Boiler Enable
Output
Boiler

Mini-MOD & Mini-Extension Installation Manual 11
WIRING TO MODULATING MOTORS
WIRING THE 4-20MA MODULATING MOTORS (A TERMINALS 13, 14), (B TERMINALS 16, 17),...
• The Mini-MOD can operate up to four 4-20 mA modulating motors.
• The Mini-Extension can operate up to six 4-20 mA modulating motors.
• The Mini-MOD and the Mini-Extension sources 24VDC excitation voltage for the 4-20mA signal.
• Wire the (-) from the modulating motor to the boiler terminal on the Mini-MOD marked (GND). That is for
boiler A, the modulating (-) terminal will be 13.
• Wire the (+) from the modulating motor to the boiler terminal on the Mini-MOD marked (mA). That is for
boiler A, the modulating (-) terminal will be 14.
13 15
14 1
7
16
-+
+
mA
GND VLT
CUR / VLT
A
-+
mA
GND
CUR/
V
B
Boiler 4-20mA
Modulation Output
4-20mA
Burner
Motor
-+
WIRING THE VOLTAGE MODULATING MOTORS (A TERMINALS 13, 15), (B TERMINALS 16, 18),...
• The Mini-MOD can operate up to four 0-5V, 0-10V, 1-5V, or 2-10V modulating motors.
• The Mini-Extension can operate up to six 0-5V, 0-10V, 1-5V, or 2-10V modulating motors.
• Wire the (GND) from the modulating motor to the boiler terminal on the Mini-MOD marked (GND). That is
for boiler D, the modulating (GND) terminal will be 22.
• Wire the (V+) from the modulating motor to the boiler terminal on the Mini-MOD marked (VLT+). That is for
boiler D, the modulating (V+) terminal will be 23.
22
20
9
21 24
23
+
+
mA
DVLT
-+
+
mA
GNDVLT
+
mA
U
R / VLT
C
CUR / VLT
D
BoilerVoltage
Modulation Output
Voltage
Burner
Motor
GNDV+
CONNECTING TO THE MINI-EXTENSION PANELS
• The Mini-MOD is equipped with a 6-pin phone socket to connect to extension panels.
• The Mini-Extension is equipped with two 6-pin phone sockets to connect to Mini-MOD and an additional
Mini-Extension panel.
• Only 6-wire phone cable must be used for proper operation.
• Connection cable is provided as part of the Mini-Extension package.
• Phone cables must be of a 6-wire with 6-pin terminals. Phone cables can extend up to 100'.
Extension Module
Full Modulation Sequencing Extension
F
H
J
Power
CAUTION: Risk of Electric Shock.
More than one disconnect switch may be required
to de-energize the equipment before servicing.
PWR
LN
12
E
34
F
56
G
78
H
910
I
11 12
EXTENSION
MODULE
RS-485
Ext A
INPUT RATINGS:
115VAC 60Hz, 12VA MAX
Use Copper Conductors Only.
OUTPUT RATINGS:
120VAC, 6A RESISTIVE
1A PILOT DUTY, 15A TOTAL
FOR ALL CIRCUITS
ENCLOSED
ENERGY
MANAGEMENT
EQUIPMENT
LISTED
99RA
CUS
E
G
I
Comm
Ext B
K
M
O
L
N
P
1514
VLTmA
CUR / VLT
181716
VLTmAGND
CUR / VLT
212019
VLTmAGND
CUR / VLT
242322
VLTmAGND
CUR / VLT
J
11 12
KMO
LNP
EFGH
KM
LN
13
GND
16
GND
19
GND
22
GND
2726
VLTmA
CUR / VLT
302916
VLTmAGND
CUR / VLT
25
GND
28
GND
IJ
OP
Mini-MOD Extension A
Extension Module
Full Modulation Sequencing Extension
F
H
J
Power
CAUTION: Risk of Electric Shock.
More than one disconnect switch may be required
to de-energize the equipment before servicing.
PWR
LN
12
E
34
F
56
G
78
H
910
I
11 12
EXTENSION
MODULE
RS-485
Ext A
INPUT RATINGS:
115VAC 60Hz, 12VA MAX
Use Copper Conductors Only.
OUTPUT RATINGS:
120VAC, 6A RESISTIVE
1A PILOT DUTY, 15A TOTAL
FOR ALL CIRCUITS
ENCLOSED
ENERGY
MANAGEMENT
EQUIPMENT
LISTED
99RA
CUS
E
G
I
Comm
Ext B
K
M
O
L
N
P
1514
VLTmA
CUR / VLT
181716
VLTmAGND
CUR / VLT
212019
VLTmAGND
CUR / VLT
242322
VLTmAGND
CUR / VLT
J
11 12
KM O
LNP
EFGH
KML N
13
GND
16
GND
19
GND
22
GND
2726
VLTmA
CUR / VLT
302916
VLTmAGND
CUR / VLT
25
GND
28
GND
IJ
OP
Mini-MOD Extension B
Connecting Mini-MOD to
Two Extension Panels
using RS485
Mini-MOD
Mini-MOD
SYSTEM
A
B
C
D
Full Modulation Sequencing Control
12
RUNPROGRAM
DO NOT APPLY ANY VOLTAGE
TO INPUT TERMINALS
34567891011 12 1315
14 17
161822
20
19 21
24
23 29
25 27
26 28 32
30 31
LN
-+
+
TT
OORS-485
mA
GNDVLT
SYSABCD
PWR
CUR /VLT
A
-+
+
mA
GND VLT
-+
+
mA
GNDVLT
-+
+
mA
GNDVLT
+
mA
TEMP
OUTDOOR
OO
TEMP
SYSTEM
EXTENSION
MODULE
CUR/VLT
B
CUR/VLT
C
CUR/VLT
D
------
PROVE
/DHW
SHUTDOWN
/SETBACK
FOR ALL CIRCUITS
120VAC, 6A RESISTIVE
OUTPUT RATINGS:
1A PILOT DUTY, 15A TOTAL
115VAC 60Hz , 30VA MAX
INPUT RATINGS:
USECOPPERWIRE,
CLASS 1 WIRE ONLY.
ENCLOSED
ENERGY
MANAGEMENT
EQUIPMENT
LISTED
99RA
CAUTION: RISK OF ELECTRIC SHOCK
More than one disconnect switch may be required
to de-energize the equipment before servicing.

12 Heat-Timer Corp.
----------- SETTINGS ------------
Season Winter
Set Point 70 F
<System Settings>
<Maintenance>
<Histories>
<System Startup>
BACK SELECT BACK SAVE
------------- SEASON --------------
Winter
Summer
BACK SAVE
------------ SET POINT ----------
70 F
[]
--------- RESET RATIO ----------
1.00 OD=4.00 Sys
1.00 OD=3.00 Sys
1.00 OD=2.00 Sys
1.00 OD=1.50 Sys
1.00 OD=1.25 Sys
1.00 OD=1.00 Sys
1.25 OD=1.00 Sys
1.50 OD=1.00 Sys
2.00 OD=1.00 Sys
3.00 OD=1.00 Sys
4.00 OD=1.00 Sys
BACK SAVE
BACK START
-------- SYSTEM STARTUP ------
(START)
to continue
BACK
CONTINUE
------------- WARNING ------------
THESE SETTINGS
CHANGE PRIMARY
SYSTEM FUNCTIONS.
BACK SAVE
-------- ARE YOU SURE? -------
No
Yes
BACK SAVE
---------- SENSOR TYPE ---------
Set Point F
Set Point C
Reset F
Reset C
BACK SAVE
------- OUTPUT A TYPE --------
4-20ma
0-10v
0-5v
2-10v
1-5v
BACK SAVE
------- OUTPUT D TYPE --------
4-20ma
0-10v
0-5v
2-10v
1-5v
BACK SAVE
------ MODULATION MODE ------
Normal
Parallel
BACK SAVE
--------- SETBACK MODE --------
Day/Night Schedules
External Signal
BACK SAVE
--------- SENSOR FAULT --------
All Off
All On

 
BACK SAVE
------- OUTDOOR CUTOFF -------
65 F
[]
BACK SAVE
-------------- OFFSET -------------
+0
F
[]
BACK SAVE
--- MINIMUM WATER TEMP ----
70
F
[]
BACK SAVE
--- MAXIMUM WATER TEMP ----
240
F
[]

BACK SAVE
----- PROVE/DHW SHARING ----
Prove
DHW Without Priority
DHW With Priority
BACK SAVE
---------- BOOST MODE ---------
30 Minutes
Disabled




BACK NEXT
--- SYS= 91 F, 10:57Am ---
BACK
EXIT
--- OD= 54 F, 11:36Am ---
BACK SAVE
------ EMS INPUT MODE -------
Disable
Enable
Reset Options
Set Point
BACK SAVE
----- EMS 20ma SETPOINT-----
220
F
[]
BACK SAVE
------ EMS 4ma SETPOINT------
120
F
[]
MENU SEQUENCE

Mini-MOD & Mini-Extension Installation Manual 13
---------
--SETTINGS-
-----
------
Seas
onWint
er
SetPoint
70F
<SystemS
ettings>
<M
aintenanc
e>
<H
istori
es>
<
SystemStar
tup>
BACKS
ELECT
BACKSAV
E
--------
--------GA
IN-------
-------
+0F
[]
BACKSEL
ECT
------
----SETTI
NGS1------
----
Gain+0
Lead
RotationT
ime
Pu
rgeDelay0
.0min
LagDe
lay0min
<M
oreSetting
s>
BACKSE
LECT
------
----SETTI
NGS2------
----
Stand
byTime10m
in
SystemR
un-On0min
S
etback0F
L
astStageHo
ld0F
SetTi
me12:03Pm
<Day/Nigh
tSche
dules>
BACKS
ELECT
---DAY/NIG
HTSCHE
DULES---
Se
tTime**:*
*
DayS
chedule**:*
*
Nigh
tSchedule*
*:**
BACK
SAVE
--
------LEA
DROTATIO
N-----
--
Manual
T
ime
Last-On
BACK
SAVE
----M
ANUALLEAD
STAGE----
A
B
C
D
E
BACKS
AVE
---AUTO
ROTATE
PERIOD---
24hrs
[]
BACK
SAVE
-----
----PURGEDE
LAY------
---
0.0min
[
]
BACKSAVE
----------
-LAGDELAY
-----------
0
min
[]
SYSTEM SETTINGS1
SYSTEM SETTINGS2
BACKSAVE
-
-------ST
ANDBY DELA
Y--------
10
min
[]
BACK SAVE
--------S
YSTEM
RUN-ON----
----
0
min
[]
B
ACKSAVE
----
----------
SETBACK--
---------
0F
[]
BACKSAVE
--
----L
ASTSTAGEH
OLD------
0F
[]
BACK SA
VE
-----
SET PR
ESEN
T TIME----
-
11:**Pm
EXTERNAL SETBACK
Schedule
BACKSELEC
T
--------
--MAINTENA
NCE--
-------
Sy
stemTrim+0F
OutdoorTri
m+0F
S
oft-OffDe
lay4
5sec
<Outpu
tTrim>
<Configur
ation>
MAINTENANCE
BACKSAVE
--
-SYST
EMSENSORT
RIM----
+0
F
[]
BACKSAV
E
--OUTDOORS
ENSOR
TRIM----
+0
F
[]
BAC
KSAVE
-----
--SOFT-OF
FDEL
AY--------
45
sec
[]
BACK S
ELECT
----
---- STA
GEATRIM --
-----
-
Output Tr
im +0.0
<Pr
ev Stage>
<N
ext Stage>
B ACK SAV E
--------
------ STAG
EA -------
----
OUTPUT
TRIM
+0.0
[]
BACK
EXIT
-----
-CONFIGUR
ATION
2------
A=
4-20ma B=0
-10v
C=0-5
vD=2-
10v
BACK NEX
T
---
--- CONFIGU
RATION1--
----
v1.00
c
ResetF
No
rmal
D
ay/NightSche
dules
AllO
ff
CAUTION
To be able to change the Mini-MOD
settings the Program/Run Switch
must be set to Program. The switch
is located under the Enclosure
Wiring Cover for security. The
Enclosure Wiring Cover can be
securely closed using a lock.

14 Heat-Timer Corp.
STARTUP SETTINGS
PROGRAM CHANGE SETTINGS
To be able to change the Mini-MOD settings the Program/Run Switch must be set to
Program. The switch is located under the Enclosure Wiring Cover for security. The
Enclosure Wiring Cover can be securely closed using a lock.
RUNPROGRAM
STARTUP SEQUENCE
Button: MENU/<System Startup>
• When powered, the Mini-MOD performs a self-test on its components.
• After the self-test diagnostics have been successfully completed, the Mini-MOD will
initialize the panel.
• On the first power up, the System Startup screen will appear after the initialization is
complete. If it doesn’t, the Mini-MOD has already been configured.
• The System Startup menu sets the main parameters like the type of sensor, the type of
output, and the modulating mode.
BACK START
-------- SYSTEM STARTUP ------
(START)
to continue
SENSOR TYPE
Set Point °F, Set Point °C, Reset °F, Reset °C Default: Set Point ◦F
Button: MENU/<System Startup>/..../Sensor type
• Reset mode is only available if an outdoor sensor is connected to terminals 25 and 26.
DO NOT select Reset without an outdoor sensor.
• The same Heat-Timer temperature sensor can display in either °F or °C.
• If °F is selected, all temperatures and settings will be displayed in degrees Fahrenheit and
the Mini-MOD will operate as a Set Point Control in degrees Fahrenheit.
BACK SAVE
---------- SENSOR TYPE ---------
Set Point F
Set Point C
Reset F
Reset C
• If °C is selected, all temperatures and settings will be displayed in degrees Celsius and
the Mini-MOD will operate as a Set Point Control in degrees Celsius.
• Set point mode does not require an outdoor sensor. If an outdoor sensor is connected in
Set Point mode it will be used only as an outdoor cutoff point. That is, to turn the boilers
and system pump off.
BACK SAVE
------ EMS INPUT MODE -------
Disable
Enable
BACK SAVE
------ EMS 4ma SETPOINT------
120 F
[]
EMS INPUT MODE (AVAILABLE IN SET POINT ONLY)
Disable, Enable Default: Disable
Button: MENU/<System Startup>/..../EMS Input Mode
• This allows the Mini-MOD to receive an external set point from an EMS/BMS system.
• You must select the 4mA (min) and 20 mA (max) Set Points in the following screen.
• The 4mA can be set to any temperature between 70ºF to 200ºF.
• The 20mA can be set to any temperature between 90ºF to 240ºF. However, the minimum
must be 20ºF higher than the 4mA setting.
• Connect the 4-20mA EMS Control Interface to the Mini-MOD RS485 connection.
SELECTING THE OUTPUT TYPE
4-20mA, 0-5V, 0-10V, 1-5V, or 2-10V Outputs Default: 4-20mA
Button: MENU/<System Startup>/..../Output A type/Output B type
• Outputs can be configured for 4-20mA operation (current) or the voltage range can be
selected (0-5V, 0-10V, 1-5V, 2-10V).
• Check the modulating motor to determine its control requirements.
• Select the appropriate Output Type for each of the boilers. The Mini-MOD can have a
different Output type for each boiler.
BACK SAVE
------- OUTPUT A TYPE --------
4-20ma
0-10v
0-5v
2-10v
1-5v
CAUTION
A good practice after performing any Startup menu modifications is to
check all operating settings and adjustments to match the new settings.

Mini-MOD & Mini-Extension Installation Manual 15
SELECTING THE MODULATING MODE
Normal, Parallel Default: Normal
Button: MENU/<System Startup>/..../Modulating Mode
• Some boilers run more efficiently as their modulation increases. For these units, it is
more energy efficient to run one unit in high than several units at lower modulation. If
your units are of this type, select Normal. This is the recommended setting for typical
steel and cast iron boilers.
BACK SAVE
------ MODULATION MODE ------
Normal
Parallel
• There are some units that run more efficiently at lower modulation. If it is more energy efficient to run several units at lower
modulation than one at high, select Parallel. This is typically used on copper boilers, low mass boilers, or burners with high
turndown ratios.
BACK SAVE
----- PROVE/DHW SHARING ----
Prove
DHW Without Priority
DHW With Priority
PROVE/DOMESTIC HOT WATER (DHW)
Prove, DHW Without Priority, DHW With Priority Default: Prove
Button: MENU/<System Startup>/..../Prove-DHW Sharing
• Input Terminals 29 and 30 can be used with either of the above features.
• When Prove is selected, the Mini-MOD will not start any boiler stage unless Prove
terminals are connected.
• Using those terminals to connect to an aquastat for a Domestic Hot Water call and selecting either of the DHW options will
raise the calculated water temperature to the lower of 200°F or Max Water Temperature.
• Domestic hot water without priority allows the SYS relay, mostly controlling a primary system pump, to remain energized
during a domestic hot water call (aquastat call on terminals 29 and 30). In Summer or when outdoor temperature is above
Outdoor Cutoff, a DHW call will energize the SYS relay. After the DHW call termination, the SYS relay will continue to run
for the System Run-On period before turning off.
• However, domestic hot water with priority de-energizes the SYS relay during a domestic hot water call (aquastat call on
terminals 29 and 30) for a period of one hour. If after the hour period the DHW call still exist, the SYS relay will energize and
the Mini-MOD will continue in the higher temperature setting until the domestic hot water call has terminated.
BACK SAVE
--------- SETBACK MODE --------
Day/Night Schedules
External Signal
SETBACK MODE
Day/Night Schedules, External Signal Default: Day/Night Schedules
Button: MENU/<System Startup>/..../Setback Mode
• The Mini-MOD has two levels of heat, a Normal/Day and a Setback/Night. The Normal
is good for when buildings are occupied and people are active. The Setback/Night holds
a lower system temperature and is for when buildings are unoccupied or inactive.
• The Day/Night Schedules provides the user with a Day Time setting for normal operation and a Night Time setting for setback.
• The External Signal option switches the Mini-MOD to Setback mode when an external signal is received through the Setback
terminals. This is allows the Mini-MOD to be managed by an external device or control to provide setback.
BACK SAVE
---------- BOOST MODE ---------
30 Minutes
Disabled
BOOST MODE
30 Minutes, Disabled Default: 30 Minutes
Button: MENU/<System Startup>/..../Boost Mode
• If you do not want a Boost simply select Disabled from the Boost Menu.
• Boost is only available if Day/Night Schedules is selected as a Setback option.
• The morning Boost is designed to return the building to comfortable ambient temperatures after the cooler Night (Setback)
period. The Mini-MOD will accomplish this by running elevated water temperatures (will add Setback setting to calculated
water temperature) for 30 minutes before the start of the Day schedule setting. That is, if the normal day set point at a specific
outdoor was 145˚F and the Setback setting was 20˚F, the boost will raise the system calculated temperature to 165˚F for 30
minutes before the start of the Day Schedule setting.
SENSOR FAULT
All Off, All On Default: All On
Button: MENU/<System Startup>/..../Sensor Fault
The Sensor Fault will determine the operating status of all output stages that are set to Auto
when a sensor reads Short or Open.
BACK SAVE
--------- SENSOR FAULT --------
All Off
All On

16 Heat-Timer Corp.
RESET MODE
• When All-On is selected, the Mini-MOD will turn all boilers On to a 100% when System reads Short or Open and Outdoor is
below Outdoor Cutoff. When Outdoor reads Short or Open, the Mini-MOD will turn all boilers On to a 100%.
• When All-Off is selected, the Mini-MOD will turn all boilers Off when either System or Outdoor sensor reads Short or Open.
SET POINT MODE
• When All-On is selected, the Mini-MOD will turn all boilers On to a 100% when the System sensor reads Short or Open.
• When All-Off is selected, the Mini-MOD will turn all boilers Off when the System sensor reads Short or Open.
• The Outdoor Sensor Short or Open status will not affect the control operation in Set Point mode.
OPERATING SETTINGS
PROGRAM CHANGE SETTINGS
To be able to change the Mini-MOD settings the Program/Run Switch must be set to
Program. The switch is located under the Enclosure Wiring Cover for security. The
Enclosure Wiring Cover can be securely closed using a lock.
RUNPROGRAM
BACK SAVE
------------- SEASON --------------
Winter
Summer
CAUTION
DO NOT turn power off to the
Mini-MOD when heating season
is over. If you do so, the battery
will run down and will have to
be replaced. Instead switch to
Summer.
SEASON
Winter, Summer Default: Winter
Button: MENU/Season
• The Mini-MOD will turn all boiler relays off when it is in Summer setting. However, a
DHW call will bring boilers back on if needed. The Message Display Line will display
Summer to show status.
• When in Winter, the Mini-MOD will activate the Sys relay whenever the Outdoor
temperature (OD) falls to or below the Outdoor Cutoff setting. In addition, it will begin
heating whenever the System temperature (SYS) falls below the Set Point Temperature.
The Message Display Line will not display any season information when in Winter.
• When the heating season is over, it is a good practice to switch the Mini-MOD to
Summer setting. This will allow DHW calls to operate the boilers when needed.
SET POINT (NOT ADJUSTABLE IN EMS MODE)
Adjustable 70ºF - 250ºF Default: 70ºF
Button: MENU/Set Point
• The Set point is the temperature value the Mini-MOD will use to control the system.
• The Mini-MOD will increase, decrease or hold the modulation of the boilers to maintain
the system temperature around the Set point.
• The system can be expected to fluctuate around the set point. The amount of fluctuation
depends on the Modulation Mode, System Settings, and Stage Settings.
• If the EMS Mode was Enabled, the Set Point will be set by the EMS/BMS system and
will be available to be read but not changed on the display.
BACK SAVE
------------ SET POINT ----------
70 F
[]
RESET RATIO
Adjustable 1.00ºOD : 4.00ºSys to 4.00ºOD : 1.00ºSys Default: 1.00ºOD : 1.00ºSys
Button: MENU/Set Point
• The Reset Ratio determines how the System water temperature (SYS) will vary with
Outside temperature (OD). With any of the ratios, the colder it becomes outside,
the hotter the temperature of the system water. The ratios are adjustable from 1.00
(OD):4.00 (SYS) to 4.00 (OD):1.00 (SYS). (See Understanding Operation Concept on
page 5)
• With a 1.00 (OD):4.00 (SYS) ratio, the System water temperature (SYS) will increase
rapidly as the outside temperature falls, hitting the maximum of 240°F at 24°F outside
temperature. With a 4.00 (OD):1.00 (SYS) ratio, the System water temperature (SYS)
will increase slowly as the outside temperature falls. Even at -30°F, the system water
--------- RESET RATIO ----------
1.00 OD=4.00 Sys
1.00 OD=3.00 Sys
1.00 OD=2.00 Sys
1.00 OD=1.50 Sys
1.00 OD=1.25 Sys
1.00 OD=1.00 Sys
1.25 OD=1.00 Sys
1.50 OD=1.00 Sys
2.00 OD=1.00 Sys
3.00 OD=1.00 Sys
4.00 OD=1.00 Sys
BACK SAVE

Mini-MOD & Mini-Extension Installation Manual 17
will only be 125°F, and at 24°F outside, the system water will be 112°F. Such a low Reset
Ratio might be used with radiant floor heating applications.
• With most baseboard heating applications, a 1.00 (OD):1.00 (SYS) setting is a good
place to start. With a 1.00 (OD):1.00 (SYS) ratio, for every degree the outside
temperature falls, the system water temperature is increased one degree.
• If required: Adjust the RESET RATIO in cold weather. If the ambient building
temperatures are too cold in cold weather, move the ratio to a higher selection. That is,
if 1.00 (OD):1.00 (SYS) was initially selected, change the selection to 1.00 (OD):1.25
(SYS). If the building temperatures are too warm in cold weather, move the ratio to
a lower selection. That is, if 1.00 (OD):1.00 (SYS) was initially selected, change the
selection to 1.25 (OD):1.00 (SYS).
Outdoor Temperature
Water Temperature
70 405060
130
120
110
100
1:4 1:1
4:1
Colder
Warmer
OUTDOOR CUTOFF TEMPERATURE
Adjustable Off, 20ºF - 100ºF, On Default: 65ºF
Button: MENU/Set Point/Outdoor Cutoff in Set Point
Button: MENU/Set Point/Offset/Outdoor Cutoff in Reset
• If the outdoor sensor is installed, the Outdoor Cutoff screen will automatically appear
after the temperature Set Point has been selected.
• When the outdoor temperature falls to the adjustable Outdoor Cutoff temperature, the
Mini-MOD will control and modulate Boilers to hold the calculated temperature.
BACK SAVE
------- OUTDOOR CUTOFF -------
65 F
[]
• When the outdoor temperature rises to the Outdoor Cutoff plus a 2°F differential, the Mini-MOD will turn all boilers off. The
System relay will remain energized for the Run-On delay then de-energize.
• The Outdoor Cutoff can be set from 20°F to 100°F. In addition, the Setting can be set to ON or OFF. In the ON position, the
System Relay will run regardless of the Outdoor temperature (OD) and the burner stages will be active to hold the calculated
water temperature. (Note: The lowest water temperature the Mini-MOD will circulate is 70°F. If the Outdoor Cutoff is turned
ON and the Season is set to Winter, the Mini-MOD will circulate at least 70°F water even in the hottest of weather.) In the OFF
position, the system pump will always be off and all burner stages will be off.
OFFSET
Adjustable 50ºF - (-50ºF) Default: 0ºF
Button: MENU/Set Point/Offset in Reset only
• The Offset setting lets you adjust the starting points of the Reset Ratio curves. This
means that, regardless of the Outdoor temperature (OD), or the Reset Ratio that has
been selected, when the Offset setting is changed, that change is directly added to or
subtracted from the calculated temperature. For example, if the Set Point temperature
was 130°F and the Offset was changed from 0° to 10° (an increase of 10°), then the Set
Point temperature would increase to 140°F
BACK SAVE
-------------- OFFSET -------------
+0 F
[]
• The Offset setting does not change the ratio selection. For instance, with 1.00 (OD):1.00 (SYS) Reset Ratio, the System water
temperature (SYS) will always increase one degree for each degree change in the Outdoor temperature (OD). What the Offset
does is add or subtract a constant temperature value. (See Understanding Operation Concept)
• If required: Adjust the Water Offset in mild weather. If the ambient building temperatures are too warm in the mild weather,
decrease the Water Offset. If the ambient building temperatures are too cold in the mild weather, increase the Water Offset. The
rule of thumb for baseboard radiation is to change the Offset 4°F for every 1°F you wish to change the building temperatures.
In radiant heat applications, change the Offset 1°F or 2°F for every 1°F you wish to change the building temperature.
BACK SAVE
--- MINIMUM WATER TEMP ----
70 F
[]
MINIMUM WATER TEMP
Adjustable 70ºF - 180ºF Default: 70ºF
Button: MENU/Set Point/Offset/Outdoor Cutoff/Minimum Water Temp in Reset only
• The Minimum Water Temperature must be set to the boiler manufacturer’s specification.
The Mini-MOD will calculate the Set Point based on the Outdoor temperature (OD), the
Reset Ratio, and the Offset value. The Mini-MOD will control all boilers modulation to
hold either the Set Point temperature, or the Minimum Water Temperature, whichever is higher.
• The Minimum Water Temperature must be at least 20°F lower than the Maximum Temperature (See next setting).

18 Heat-Timer Corp.
MAXIMUM WATER TEMP
Adjustable 90ºF - 240ºF Default: 240ºF
Button: MENU/Set Point/Offset/..../Maximum Water Temperature in Reset only
• This is the highest temperature heating water the Mini-MOD will circulate through the
heating system. It is available in Reset mode only.
• When using a radiation system, it should be set according to the tubing or floor
manufacturer’s specification.
• The Maximum Temperature must be at least 20°F higher than the Minimum Temperature.
BACK SAVE
--- MAXIMUM WATER TEMP ----
240 F
[]
SYSTEM SETTINGS
Button: MENU/<System Settings>
The Settings 1 and Settings 2 menus provide access to adjusting and fine-tuning the system for
enhanced comfort and more fuel savings. The Mini-MOD behaves differently based on the
selected Control Modes (see Startup Settings).
BACKSE
LECT
--------
--S
ETTING
S1-----
-----
Ga
in+0
Le
adRotat
ion
Time
Pur
geDela
y0.
0min
Lag
Delay0
min
<Mor
eSetti
ngs>
BA
CKSELEC
T
-----
-----SE
TTINGS
2---
------
-
Stand
byTime1
0min
Sy
stemRun
-On
0min
Setbac
k0F
Las
tSta
geHold
0F
SetT
ime12:
03Pm
<D
ay/N
ight
Sch
edul
es>
RUNPROGRAM
• Gain
• Lead Rotation
• Purge Delay
• Lag Delay
• Standby Time
• System Run-On
• Setback
• Last Stage Hold
• Day/Night Schedules
CAUTION
To be able to change the Mini-MOD settings the Program/Run Switch must be
set to Program. The switch is located under the Enclosure Wiring Cover for
security. The Enclosure Wiring Cover can be securely closed using a lock.
GAIN
Adjustable -10 to +10 Default: 0
Button: MENU/<System Settings>/Gain
• The Gain adjusts the aggressiveness of the Mini-MOD PID logic to control how much
modulation is changed when the system temperature is different from the Set Point.
• A Gain of 0 is a good starting point for all systems.
• If during normal load conditions, the system temperature tends to fluctuate significantly,
decrease the Gain by two numbers (for example, from 0 to -2). Wait for at least 15
minutes before evaluating how the change has affected the system.
• If, during normal load conditions the system temperature tends to remain consistently
below the Set Point (or consistently above the Set Point), increase the Gain by two
numbers (for example, from 0 to 2). Wait for at least 15 minutes before evaluating how
the change has affected the system.
BACKSA
VE
--
------
------
--GAIN -
---
-------
---
+0
F
[ ]
BACK SA VE
----
----LEA
D RO
TATION
-------
Man
ual
T ime
Last-O
n
BACK SA
VE
----
MANUAL L
EAD STAG
E----
A
B
C
D
E
BAC KSA
VE
--- A UTO ROTA TE PERI OD -- -
24 hrs
[ ]
LEAD BOILER ROTATION
Adjustable Manual, Time (1 hr to 60 Days), Last-On Default: Time (24Hours)
Button: MENU/<System Settings>/Lead Rotation
• The Lead Boiler is the first boiler brought on when output is required.
• The Lead Boiler can be rotated automatically, manually or based on Last-On. The
automatic rotation is recommended.
• The current Lead Boiler is shown in brackets on the main display.
• Only Boilers which are set to Auto Mode can be Lead. Therefore, not all the Boilers may
be available when manually selecting a new Lead Boiler.

Mini-MOD & Mini-Extension Installation Manual 19
PURGE DELAY
Adjustable 0.0min to 10.0min Default: 1.0min
Button: MENU/<System Settings>/Purge Delay
• Many boilers go through a purge cycle before they are brought on line.
• When the Mini-MOD activates a boiler, it does not start to calculate its output until the
Purge Delay is over. This allows the boiler to fully come on line and begin producing
output.
• The Purge Delay helps to prevent short cycling of a newly activated burner. Once the
burner is activated, it MUST run through the entire Purge Delay period.
• The minimum Purge Delay setting MUST be set to the time required by the boiler
manufacturer. Time entry is in 0.1 of a minute (i.e. 1.5min will equal 90 seconds.)
• The Message Display Line will display Purge Delay and the amount of time remaining
in the purge.
BACK
SAVE
---
------
PURGEDEL
AY-----
----
0.0min
[]
CAUTION
Set Purge Delay as per boiler
manufacturer recommendation.
LAG DELAY
Adjustable 0min to 60min Default: 0min
Button: MENU/<System Settings>/Lag Delay
• The Lag Delay requires the previous stage to remain at 100% modulation for the full
period of the Lag Delay before another Stage can be activated. For example, if the Lag
Delay was set to 10 minutes, the Lead Stage would need to remain at 100% modulation
for a full ten minutes (never backing down to even 99%) before a lag stage could be
activated. The Message Display Line will display Lag Delay and the remaining time.
BAC
KSAVE
-
-------
---LAG
DELAY--
------
---
0
min
[]
• Set the Lag Delay to 0 min when two or more Stages will generally be needed to hold the load.
• The Lag Delay is useful in installations where one unit should usually have enough output to hold the load unless it fails or load
conditions become extreme.
• The Lag Delay overrides the value of the Modulation Point selected for each stage. Regardless of that setting, the previous stage
must reach 100% and stay there before another Stage can be activated.
• The full Lag Delay must always elapse regardless of what happens to system temperature. Therefore, set the Lag Delay to 0 min
if you want smooth set point control using multiple units.
STANDBY TIME
Adjustable 1min to 60min Default: 10min
Button: MENU/<System Settings>/<More Settings>/Standby Time
• The Standby Delay Time only applies to Boilers in Standby Mode.
• A boiler can be set to be a Standby boiler using the Stage Menu.
• A Standby Boiler can only be activated after all the boilers in Auto Mode have run at
100% modulation for the full Standby Time.
• Standby boilers are used for backup or extreme load conditions only. A Standby Boiler
can never be a Lead Stage
BACK
SAVE
--
------
STANDBY
DELAY--
------
1
0min
[]
• The full Standby Delay Time must always elapse regardless of what happens to system temperature. Therefore, shorter Standby
Times will result in smoother set point operation in extreme conditions. Longer Standby Times may prevent a Standby Boiler
from firing if the other boilers can eventually meet the load, or if the load decreases.
SYSTEM RUN-ON
Adjustable 0min to 360min Default: 0min
Button: MENU/<System Settings>/<More Settings>/System run-On
• The SYS relay will energize whenever the Outdoor temperature (OD) is below the
Outdoor Cutoff. When the Outdoor temperature increases 2°F above the Outdoor Cutoff
after the last burner relay has de-energized, the SYS relay will stay on for a period set
by the System Run-On. This allows the Pump to dissipate the residual heat within the
boilers back into the system.
BACK
SAVE
------
-- SYSTE
MRUN-O
N--
------
0 min
[ ]

20 Heat-Timer Corp.
• A common use for the System Run-On is to control a system pump in a heating system. The extra time helps transfer the heat
from the boilers to the heating system.
• The System Run-On time should be set based on the size and type of the boilers and pumps. In general, a boiler with low
water content and high horsepower will need a longer System Run-On than a boiler with the same horsepower and more water
content. (Refer to boiler manufacturer recommendation)
SETBACK
Adjustable 0°F to 75°F Default: 0°F
Button: MENU/<System Settings>/<More Settings>/Setback
• The Setback feature can be used to provide the Mini-MOD with a lower temperature Set
Point when less load is required.
• The lower Set Point will appear on the main display indicating this condition.
• For example, if the calculated temperature is 180°F and the Setback is 20°F, then when
in Setback, the Mini-MOD will hold a Set Point of 160°F.
• A typical use for Setback is to provide less system temperature to a building during the
night or on the weekends when building is not occupied, but heat is still required.
BACKSAVE
------
--------
SET
BACK--
----
-----
0
F
[]
• The amount of Setback selected is subtracted from the Set Point when a Setback External Signal is received or the Night Time
schedule setting started.
• If External Signal is selected as a Setback Mode (See Startup menu), the Setback will not be activated unless a dry contact
signal source is wired into the Shutdown/Setback terminals (31 and 32) and the Mini-MOD receives a SHORT signal.
• If Day/Night Schedules is selected as a Setback Mode (See Startup menu), the Setback will be activated only when Night
Schedule time has started.
CAUTION
When using Soft-Off and Last Stage Hold, the last boiler stage will not turn off
until both parameters have elapsed. In this case, Soft-Off will start after the Last
Stage Hold.
LAST STAGE HOLD
Adjustable 0°F to 30°F Default: 0°F
Button: MENU/<System Settings>/<More Settings>/Last Stg Hold
• The Last Stage Hold prevents short cycling of the Lead Stage during low load periods.
• In low load conditions, the system might require only 5% of the output of one Stage.
When the Mini-MOD brings on the Lead Stage, the Set Point is quickly exceeded, and
the Mini-MOD turns the Lead Stage off.
• To prolong the run time during this type of condition, use the Last Stage Hold setting.
• The Mini-MOD will let the system temperature exceed the Set Point by the number of
degrees selected, before the Lead Stage is turned off.
• For example, with a Set Point of 160°F and a Last Stage Hold setting of 10°F, the Lead
Stage boiler will remain on, at low modulation, until the Set Point reaches 170°F.
• From an efficiency standpoint, it is better to overshoot slightly than to short cycle a
boiler.
BACKSA
VE
-
----
-LA
STSTAG
EHOLD--
----
0
F
[]
WARNING
The temperature limits set on
the boilers must be higher than
the Mini-MOD Set Point. Read
the section at left for details
that will prevent erratic system
operation.
Avoiding Conflicting Boiler Limits
• The temperature limits set on the boilers MUST be set considerably higher than the
Mini-MOD’s Set Point for the reasons detailed below.
• The Mini-MOD sensor is located in a common header some distance from the boilers.
• As the temperature rises in the header and before reaching the sensor location, energy is
dissipated. Therefore, the temperature in the header could be lower than that registered
by boiler sensors.
• In addition to the normal drop experienced between the boiler’s temperature and that