Page 1
Laars Sequencing Controls
SYSTEM
DHW PUMP
INPUT RATINGS:
115VAC 60Hz, 12VA MAX
Use Copper Conductors Only.
CAUTION:
Risk of Electric Shock.
PWR
L N
1 2
SENSORS MUST BE GOLD SERIES
SYSTEM
3
DHW
PUMP
5
Stage A7Stage B9Stage C
11
13
Stage E15Stage F
17
Stage D
6 8 10 12 14
16 18
RS485
SYS=144F OD=35F
<AB
> DE GH JK
HI LO -- OFF
4
Stage G19Stage H
21
OUTDOOR
TEMP
27 29
31
DHW
33
SHUTDOWN
/SETBACK
35
RETURN
TEMP
20 22 28 30 32 34 36
STAGE MENU
Stage E
Stage F
Stage G
Stage H
Stage A
Stage B
Stage C
Stage D
25
26
PRESS
+ -
37
38
PROVE
SYSTEM
TEMP
PROGRAM
RUN
OUTPUT RATING: 6 AMP RESISTIVE, 1 AMP PILOT DUTY PER OUTPUT AT 120VAC.
23 24
COMB.
AIR
DO NOT APPLY ANY VOLTAGE TO INPUT TERMINALS
COMB. AIR
ENCLOSED
ENERGY
MANAGEMENT
EQUIPMENT
LISTED
99RA
C US
S8
SEQUENCING CONTROL
Sequencing
Model S8 and S8Ext
Output panel to Sequence
up to 24 individual
stages with lead-lag and
manual override capabilities
Document 4213
FOR YOUR SAFETY: This product must be installed and serviced by a
professional service technician, qualified in hot water heater/boiler controls
installation and maintenance. This manual is intended for anyone who will
install, operate or maintain the control system. Before you begin installation
and operation of this control, it is important that you thoroughly review this
manual. Improper installation and operation could result in damage to
equipment and possibly even personal injury. Laars Sequencing Controls are
not intended for use as operation safety limit controls. Another control, that is
intended and certified as a high limit control, must be in the water heater/boiler
control circuit.
Page 2
Page 2 LAARS Heating Systems
Contents
S8 LAYOUT . . . . . . . . . . . . . . . . . . . . 3
S8 OVERVIEW. . . . . . . . . . . . . . . . . . . 4
UNDERSTANDING OPERATION CONCEPT
Reset Ratio/Outdoor Reset . . . . . . . . . . . . 5
Make Sure You Have the Right Control . . . . . . . 6
. . . 5
INITIAL SETUP . . . . . . . . . . . . . . . . . . 6
Selecting the System Features . . . . . . . . . . . 6
INSTALLATION . . . . . . . . . . . . . . . . . . 7
Mounting the Enclosure . . . . . . . . . . . . . . . 7
Install the Sensors . . . . . . . . . . . . . . . . . . 8
System Sensor Installation . . . . . . . . . . . . 8
Outdoor Sensor Installation . . . . . . . . . . . . 8
Wiring . . . . . . . . . . . . . . . . . . . . . . . . 9
Wiring the Power (Terminals 1, 2) . . . . . . . . . 9
Wiring the Sensors. . . . . . . . . . . . . . . . . 9
Wiring the Domestic Hot Water (DHW) Sensor
(Terminals 33, 34) . . . . . . . . . . . . . . . . . 10
Wiring the Shutdown (Terminals 35, 36) . . . . . . 10
Wiring the Setback (Terminals 35, 36) . . . . . . . 10
Wiring the Prove (Terminals 37, 38) . . . . . . . . 10
Wiring the System Output (Terminals 19, 20) . . . 10
Wiring the DHW Pump (Terminals 21, 22) . . . . . 11
Wiring the Comb. Air Damper (Terminals 23, 24) . 11
Wiring the Stage (Terminals 3, 17). . . . . . . . . 11
MENU SEQUENCE . . . . . . . . . . . . . . . 12
Connecting to S8EXT Panels and XSIG Interface 15
Startup Settings . . . . . . . . . . . . . . . . . . . 16
Program Change Settings . . . . . . . . . . . . . 16
Startup Sequence . . . . . . . . . . . . . . . . . 16
Control Mode . . . . . . . . . . . . . . . . . . . 16
Display Unit . . . . . . . . . . . . . . . . . . . . 16
Setting the 4mA and 20mA Set Points (Available in 4-
20mA EMS only) . . . . . . . . . . . . . . . . . . 16
Application . . . . . . . . . . . . . . . . . . . . . 17
DHW Piping (Available with Heating Only) . . . . 17
DHW Pump Output . . . . . . . . . . . . . . . . 17
Combustion Air Damper Output . . . . . . . . . . 17
Setback Mode . . . . . . . . . . . . . . . . . . . 17
Burner Type . . . . . . . . . . . . . . . . . . . . 18
Boiler Output . . . . . . . . . . . . . . . . . . . . 18
Total Boilers . . . . . . . . . . . . . . . . . . . . 18
Staging. . . . . . . . . . . . . . . . . . . . . . . 18
Sequence . . . . . . . . . . . . . . . . . . . . . 18
Control Logic. . . . . . . . . . . . . . . . . . . . 18
Sensor Fault . . . . . . . . . . . . . . . . . . . 194
Operating Settings . . . . . . . . . . . . . . . . . . 20
Program Change Settings . . . . . . . . . . . . . 20
Season. . . . . . . . . . . . . . . . . . . . . . . 20
Reset Ratio . . . . . . . . . . . . . . . . . . . . 20
Customized Reset Ratio . . . . . . . . . . . . . . 20
Set Point (Not Adjustable in EMS Mode) . . . . . 21
Outdoor Cutoff Temperature
Target Offset . . . . . . . . . . . . . . . . . . . . 21
Minimum Target . . . . . . . . . . . . . . . . . . 22
Maximum Target . . . . . . . . . . . . . . . . . . 22
Boiler Minimum Return. . . . . . . . . . . . . . . . 22
Minimum Return . . . . . . . . . . . . . . . . . . 22
Return Lag . . . . . . . . . . . . . . . . . . . . . 22
System Settings . . . . . . . . . . . . . . . . . . . 23
Program Change Settings . . . . . . . . . . . . . 23
Stage Settings . . . . . . . . . . . . . . . . . . . . 23
Reaction Time . . . . . . . . . . . . . . . . . . . 23
Purge Delay . . . . . . . . . . . . . . . . . . . . 23
Minimum Runtime . . . . . . . . . . . . . . . . . 23
Standby Delay . . . . . . . . . . . . . . . . . . . 23
Last Stage Hold . . . . . . . . . . . . . . . . . . 24
Throttle Range . . . . . . . . . . . . . . . . . . . 24
Lead Settings . . . . . . . . . . . . . . . . . . . . 24
Lead Boiler. . . . . . . . . . . . . . . . . . . . . 25
Rotate Mode . . . . . . . . . . . . . . . . . . . . 25
Setback Schedule . . . . . . . . . . . . . . . . . . 25
Setback . . . . . . . . . . . . . . . . . . . . . . 25
Boost. . . . . . . . . . . . . . . . . . . . . . . . 25
Boost Period . . . . . . . . . . . . . . . . . . . . 26
Day/Night Schedules . . . . . . . . . . . . . . . 26
Set Present Time . . . . . . . . . . . . . . . . . 26
DHW Settings . . . . . . . . . . . . . . . . . . . . 27
DHW Priority Timer (Available with Parallel DHW
Piping) . . . . . . . . . . . . . . . . . . . . . . . 27
DHW Set Point (Requires an Optional DHW
Temperature Sensor) . . . . . . . . . . . . . . . 27
DHW Differential . . . . . . . . . . . . . . . . . . 27
Pump, Valve, and Combustion Air Damper Operation 28
Run-On . . . . . . . . . . . . . . . . . . . . . . 28
Pump Exercise. . . . . . . . . . . . . . . . . . . 28
Maintenance . . . . . . . . . . . . . . . . . . . . . 28
System & Outdoor Sensor Trim . . . . . . . . . . 28
History . . . . . . . . . . . . . . . . . . . . . . . . 28
Configuration. . . . . . . . . . . . . . . . . . . . 29
Display . . . . . . . . . . . . . . . . . . . . . . . 29
Stage Settings . . . . . . . . . . . . . . . . . . . . 30
Mode . . . . . . . . . . . . . . . . . . . . . . . . 30
RunTime . . . . . . . . . . . . . . . . . . . . . . 30
. . . . . . . . . . . . 21
TROUBLESHOOTING. . . . . . . . . . . . . . 31
PIPING DIAGRAM . . . . . . . . . . . . . . . . 32
WIRING DIAGRAM . . . . . . . . . . . . . . . 33
SPECIFICATIONS
: . . . . . . . . . . . . . . . 34
Page 3
LAARS Sequencing Controls S8 & S8EXT
Connect to Extension panels to
add additional stages or connect
to X-SIG Interface for
external 4-20mA set point.
When connecting Temperature Sensors, no
Polarity is observed. Prove terminals
must be connected for S8 to
operate stages.
Button function is presented on
bottom row of the display.
LEDs indicate
associated relay’s status
Program Switch to restrict access
to function changes. This Switch is
covered with Enclosure Wiring Cover.
System Output controls pumps,
valves, or other system components.
DHW Pump and Comb. Air relays are
controlled when configured.
Output Relays to manage the stages.
SYSTEM
DHW PUMP
INPUT RATINGS:
115VAC 60Hz, 12VA MAX
Use Copper Conductors Only.
CAUTION:
Risk of Electric Shock.
PWR
L N
1 2
SENSORS MUST BE GOLD SERIES
SYSTEM
3
DHW
PUMP
5
Stage A7Stage B9Stage C
11 13
Stage E15Stage F
17
Stage D
6 8 10 12 14
16 18
RS485
SYS=144F OD=35F
<AB
> DE GH JK
HI LO -- OFF
4
Stage G19Stage H
21
OUTDOOR
TEMP
27 29 31
DHW
33
SHUTDOWN
/SETBACK
35
RETURN
TEMP
20 22 28 30 32 34 36
STAGE MENU
Stage E
Stage F
Stage G
Stage H
Stage A
Stage B
Stage C
Stage D
25 26
PRESS
+ -
37 38
PROVE
SYSTEM
TEMP
PROGRAM
RUN
OUTPUT RATING: 6 AMP RESISTIVE, 1 AMP PILOT DUTY PER OUTPUT AT 120VAC.
23 24
COMB.
AIR
DO NOT APPLY ANY VOLTAGE TO INPUT TERMINALS
COMB. AIR
ENCLOSED
ENERGY
MANAGEMENT
EQUIPMENT
LISTED
99RA
C US
S8
SEQUENCING CONTROL
S8 LAYOUT
Page 3
Page 4
Page 4 LAARS Heating Systems
S8 OVERVIEW
SEQUENCES UP TO 8 STAGES WITH PUMPS OR VALVES.
The S8 is the perfect control whenever multiple boiler or chiller stages are required for hydronic heating or cooling applications. The S8
controls the stages and their pumps or valves to maintain a precise system set point.
PID OR OVER-SIZED-SYSTEM (OSS) LOGIC
The S8’s control algorithm allows it to look at the rate of change in the system. If the load is changing quickly, the S8 can be set to OSS
sequencing where it will react based on load changes. If the system fluctuations are minimal as in heating applications, the S8 will make
slow and gradual output adjustments. Therefore, the S8 adapts to specific system requirements and minimizes fluctuations around the
set point.
DIGITAL DISPLAY OF ALL SYSTEM SETTINGS
The S8’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 unit. The S8 has three modes of rotation: Manual,
FOFO, or Time. The Time rotates the lead stage every selected time period from every hour to every 41 days.
OUTDOOR RESET WITH CUSTOMIZABLE CURVE
The S8 has a hydronic outdoor temperature reset function. This allows the S8 to change the set point based on outdoor temperature.
Furthermore, a customizable outdoor reset curve has been incorporated for unique applications where standard reset ratios will not satisfy.
In addition, the following settings have been added to help fine tune all reset operation; Offset, Minimum, and Maximum Targets and
Night Setback Schedule or Setback using an External Signal.
STANDBY UNIT OPTION
Any of the S8 heating or cooling units can be configured as a Standby with an adjustable Standby delay. Assigning a specific unit to
work in standby mode will remove it from the rotation. In this mode, the unit will be used for backup in large demand periods where
the primary units will not suffice.
SYSTEM AND COMBUSTION AIR DAMPER OUTPUTS WITH PROVE INPUT
These outputs work with the control logic to operate a primary system pump and a combustion air damper. In addition, a System Prove
input can be wired in to check the status of either of the components activated by the outputs before stages can be activated.
NORMAL OR PARALLEL (LO/LO/HI/HI) SEQUENCING
The S8 can sequence heating or cooling units as needed. For heating systems where higher efficiency is achieved using lower firing
stages, the S8 offers the Parallel Sequencing option. It will sequence all the low firing stages first before bringing the rest of the stages
on. For other types of heating and cooling units, using the Normal Sequencing option will bring the lower operating stage followed by
the higher one of the lead unit. Then, will do the same with the lag unit.
MULTIPLE OR SINGLE STAGING
Unlike many boilers/water heaters where, to fire a multi-stage boiler both low and high stage relays must be energized, some of the
available cooling units require that the operation of the higher stages turn off the lower operating stages. This can be achieved by selecting
Single from the Startup Staging menu.
ADD UP TO 16 STAGES
As a stand-alone, the S8 is designed to control eight stages. However, it has the capability of expanding its control to two extension
panels each with eight stages. Thus, the S8 can control a total of up to 24 stages.
MONITOR SYSTEM RETURN TEMPERATURE
Using a smart algorithm, the S8 can monitor boiler return temperature using an optional return sensor mounted on the return line. Then,
sequence the boilers to raise above an adjustable Minimum Return.
DHW PUMP CONTROL WITH MULTIPLE PRIORITY OPTIONS
Having a DHW input either as a dry contact to be used with an external aquastat or as a temperature sensor that can be ordered separately,
the S8 can control a DHW pump using its built-in output relay. The user will have different priority options that varies based on the
DHW piping design.
Page 5
LAARS Sequencing Controls S8 & S8EXT
Outdoor Temperature
Wate r Temperature
70 405060
130
120
110
100
Outdoor Temperature
Wate r T empe ratur e
70 405060
110
100
90
80
Outdoor Temperature
Wat er Temper ature
70 405060
150
140
130
120
1:4
With a 0° Offset, the
ratio curves begin at
100° WaterTemperature.
With a -20° Offset, the
ratio curves begin at
80° WaterTemperature.
With a +20° Offset, the
ratio curves begin at
120° WaterTemperature.
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 605040 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
Reset Ratio is Presented as
Outdoor Temp. : Water Temp. Ratio
1:4
8:1
UNDERSTANDING OPERATION CONCEPT
The S8 has multiple operating modes that satisfy most hydronic systems. In heating, it can
change the System Set Point based on outdoor temperature. Or, it can sequence stages to
achieve an adjustable fixed Set Point in either heating or cooling.
In Outdoor Reset, the S8 controls a hot water heating system to provide a building with
comfortable and even heat levels. The S8 varies the temperature of the circulating heating
water in response to changes in the outdoor temperature. The heating water temperature is
controlled through the sequencing of the stages.
The S8 also controls the system circulating pump with an adjustable Outdoor Cutoff. In heating,
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. In cooling applications, the outdoor cutoff turns off the cooling
units and system pump when the outdoor temperature rises above the outdoor cutoff setting.
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.
Page 5
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 S8 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
WARNING
When controlling a non condensing
boiler, minimum boiler water
temperature must be set to boiler
manufacturer specifications. In that
case, system temperature must not
go below such temperature.
Page 6
Page 6 LAARS Heating Systems
MAKE SURE YOU HAVE THE RIGHT CONTROL
If you need the S8 to do additional tasks that either are not listed or do not know how to configure them, contact LAARS.
INITIAL SETUP
Setting an Initial Program will ease the configuration of the S8 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 S8 has been designed with Hydronic heating and cooling as the primary purpose. With this in mind, many of the S8 features can be
utilized to ease, enhance and improve your system performance. Some of these features are listed in this section.
HEATING OR COOLING WITH MULTIPLE OR SINGLE OUTPUT AT A TIME
• The S8 is equipped to control multiple multi-stage boilers with or without pumps or valves for heating application. As well, it can
be configured for cooling with multiple stage chillers.
• That, combined with the capability of energizing only a single stage of a multi-stage cooling unit when in high demand, makes the
S8 versatile for many industries.
OUTDOOR RESET, SET POINT, OR EXTERNAL 4-20MA SET POINT
• The S8 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 Outdoor Reset option uses an Outdoor Sensor (supplied with the
control) and achieves better fuel savings in addition to better comfort.
• Using an optional X-SIG Interface (CA004200), the S8 can receive an external 4-20mA Set Point through EMS system.
PID OR OSS CONTROL LOGIC
• The S8 PID can be used for applications where system reaction will require a long period to achieve or measure the results. However,
OSS, can be used for applications where the load changes frequently and the sequencing must match the load and its immediate
change.
NUMBER OF STAGES
• The S8 can be configured to control up to eight stages. It can control up to 24 stages using a maximum of two S8 Extension Panels
each with eight stages.
STAGE PUMPS OR VALVES
• The S8 can control muliple stages in addition to
CONTROL DHW PUMP AND COMBUSTION AIR DAMPER
• The control of the DHW is based on either a temperature sensor, can be purchased separately, on the DHW source or using a dry
contact from an aquastat. The S8 provides multiple DHW Priority options to choose from based on the DHW piping. The Combustion
Air Damper output can control the equipment while utilizing the Prove input to check the status on the Combustion Air Damper End
Switch, System Pump Flow switch or any other checking devices before any stage is energized.
unit pumps, valves.
MONITOR BOILER RETURN
• The optional return line sensor, can be purchased separately, can be connected in heating applications to monitor and help protect
the boilers from thermal shock and condensation caused by cool returns.
Page 7
LAARS Sequencing Controls S8 & S8EXT
Mounting Base
Display Mounting Screws Wiring Cover Mounting Screws
Enclosure Display Module
Enclosure Wiring Cover Enclosure Base
Hole for optional
Padlock (not supplied)
AUTOMATIC ROTATION AMONG BOILERS
• Rotating the lead unit to be activated on a call for output promotes even wear on all units. The S8 has three modes of rotation: Manual,
First-On-First-Off, or Timed Rotation. This option automatically rotates units every selected time period from one hour to every
41(999 hours) days.
SETBACK OR DAY/NIGHT SCHEDULING
Two Setback modes are available for the S8:
• 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 S8 in and out of setback mode.
Page 7
INSTALLATION
Each of the S8 or S8EXT 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 S8 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
S8 or S8EXT.
• 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.
• When purchasing a padlock for the enclosure, the maximum shank diameter
should not exceed ¼"
Page 8
Page 8 LAARS Heating Systems
Immersion Well
3/8" ID 1/2" NPT
Heating System
Sensor
Common Supply Pipe
Sensor Probe
Immersion Heating System Sensor
Shield
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
10' Minimum
Outdoor Sensor
Low Voltage
Sensor Wires
Sensor Clip
INSTALL THE SENSORS
SYSTEM SENSOR INSTALLATION
LOCATING THE SYSTEM SENSOR
• Put the System sensor approximately 10' feet past the last heating/cooling unit
on the common supply header but before any major takeoffs.
• The sensor must be located where it sees the output of all the stages. If a unit
is piped so that the sensor does not see its output, the S8 will not sequence the
units correctly.
• Only use a Standard Brass Tube sensor (CA002400 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 immersion well (CA002500 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.
If the System Sensor can not sense the
correct system water temperature being
supplied to the building, the S8 will not
provide comfortable heat/cool levels. Be
sure that it is located on a main supply
pipe which can not easily be isolated
from the system.
CAUTION
OUTDOOR SENSOR INSTALLATION
• Only use the Laars 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 control using the terminal
marked with an “O”.
• Do not run sensor wires in conduit with line voltage wiring.
The S8 is an operating control only. All equipment 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 S8 is installed.
Determining the proper location for the Outdoor Sensor is very
important. The S8 will base its operation 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).
WARNING
CAUTION
Page 9
LAARS Sequencing Controls S8 & S8EXT
Line
Neutral
DHW
Use Copper Conductors Only.
CAUTION:
Risk of Electric Shock.
PWR
L N
1 2
SENSORS MUST BE GOLD SERIES
SYSTEM
3
DHW
PUMP
5
Stage A7Stage B9Stage C
11 13
Stage E15Stage F
17
Stage D
6 8 10 12 14
16 18
RS485
4
Stage G19Stage H
21
OUTDOOR
TEMP
27 29 31
DHW
33
SHUTDOWN
/SETBACK
35
RETURN
TEMP
20 22 28 30 32 34 3625 26
PRESS
+ -
37 38
PROVE
SYSTEM
TEMP
PROGRAM RUN
OUTPUT RATING: 6 AMP RESISTIVE, 1 AMP PILOT DUTY PER OUTPUT AT 120VAC.
23 24
COMB.
AIR
DO NOT APPLY ANY VOLTAGE TO INPUT TERMINALS
Use Copper Conductors Only.
CAUTION:
Risk of Electric Shock.
PWR
L N
1 2
SENSORS MUST BE GOLD SERIES
SYSTEM
3
DHW
PUMP
5
Stage A7Stage B9Stage C
11 13
Stage E15Stage F
17
Stage D
6 8 10 12 14
16 18
RS485
4
Stage G19Stage H
21
OUTDOOR
TEMP
27 29 31
DHW
33
SHUTDOWN
/SETBACK
35
RETURN
TEMP
20 22 28 30 32 34 3625 26
PRESS
+ -
37 38
PROVE
SYSTEM
TEMP
PROGRAM RUN
OUTPUT RATING: 6 AMP RESISTIVE, 1 AMP PILOT DUTY PER OUTPUT AT 120VAC.
23 24
COMB.
AIR
DO NOT APPLY ANY VOLTAGE TO INPUT TERMINALS
Setback
Dry Contact
Lo Hi
Unit1
Stages
Lo Hi
Unit2
Stages
Sensor Shiled
SENSORS MUST BE GOLD SERIES
RS485
OUTDOOR
TEMP
27 29
31
DHW
33
SHUTDOWN
/SETBACK
35
RETURN
TEMP
26
37
38
PROVE
SYSTEM
TEMP
DO NOT APPLY ANY VOLTAGE TO INPUT TERMINALS
Outdoor Sensor
Prove
Dry Contact
Sensor Shiled
System Sensor
Sensor Shiled
Return Sensor
Shutdown
Dry Contact
Sensor Shiled
DHW Sensor
SENSORS MUST BE GOLD SERIES
RS485
OUTDOOR
TEMP
27 29
31
DHW
33
SHUTDOWN
/SETBACK
35
RETURN
TEMP
26
37
38
PROVE
SYSTEM
TEMP
DO NOT APPLY ANY VOLTAGE TO INPUT TERMINALS
SENSORS MUST BE GOLD SERIES
RS485
OUTDOOR
TEMP
27 29
31
DHW
33
SHUTDOWN
/SETBACK
35
RETURN
TEMP
26
PRESS
+ -
37
38
PROVE
SYSTEM
TEMP
DO NOT APPLY ANY VOLTAGE TO INPUT TERMINALS
Setback
Dry Contact
Sensor Shiled
Outdoor Sensor
Prove
Dry Contact
Sensor Shiled
DHW Sensor
RS485
OUTDOOR
TEMP
31
DHW
33
SHUTDOWN
/SETBACK
35
RETURN
TEMP
37
38
PROVE
SENSORS MUST BE GOLD SERIES
RS485
OUTDOOR
TEMP
31
DHW
33
SHUTDOWN
/SETBACK
35
RETURN
TEMP
37
38
PROVE
TEMP
DO NOT APPLY ANY VOLTAGE TO INPUT TERMINALS
Setback
Dry Contact
Sensor Shiled
RS485
31
DHW
33
SHUTDOWN
/SETBACK
35
RETURN
TEMP
37
38
PROVE
Outdoor Sensor
Prove
Dry Contact
Sensor Shiled
Sensor Shiled
Return Sensor
Shutdown
Dry Contact
Sensor Shiled
DHW Sensor
RS485
31
DHW
33
SHUTDOWN
/SETBACK
35
RETURN
TEMP
37
38
PROVE
RS485
TEMP
31
DHW
33
SHUTDOWN
/SETBACK
35
RETURN
TEMP
37
38
PROVE
Setback
Dry Contact
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.
WARNING
Class 1 voltages must enter the enclosure through a different opening from any Class 2 voltage
wiring. Laars recommends installing a surge suppressor on the power source to the S8.
Page 9
Connect the shield at the control terminal end and cut the shield wire at the sensor end.
WIRING THE SENSORS
SYSTEM TEMPERATURE SENSOR WIRING (TERMINALS 27, 28)
• A S8 must be connected to a temperature sensor located in the common header.
• The S8 is designed to be connected to a temperature sensor (CA002400 or equivalent) for immersion in a
3/8ID well (CA002500 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 S8 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 29, 30)
• When Outdoor Reset is selected, the S8 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. In
heating, the S8 will disable all Boilers when the outdoor temperature is above the adjustable Outdoor
Cutoff temperature. However, in cooling it will disable the units when the outdoor temperature is below
the Outdoor Cutoff. This feature will automatically be activated when an outdoor sensor is connected.
• For an outdoor sensor use a Laars outdoor sensor (CA002400 or equivalent).
• 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
• Connect the shield to the circled terminal 30 with one of the sensor wires.
sensor to the S8 terminals marked OUTDOOR TEMP - 29, 30.
WARNING
RETURN SENSOR WIRING (TERMINALS 31, 32) OPTIONAL (AVAILABLE IN HEATING ONLY)
• If the Return Sensor is connected, must be purchased separately, the S8 will recognize
it and alternate its temperature on the display with the Target temperature. If the Return
is below the Minimum Return, the S8 will sequence stages based on the Return Sensor,
Minimum Return, Calculated Target, and the actual System Temperature.
• The Return on the S8 is designed to be connected to a temperature sensor that can be purchased
separately (CA002400 or equivalent) for immersion in a 3/8ID well (CA002500 or equivalent).
• 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 S8 terminals marked OUTDOOR TEMP - 31, 32.
• Connect the shield to the circled terminal 32 with one of the sensor wires.
Page 10
Page 10 LAARS Heating Systems
Sensor Shiled
Prove
Dry Contact
Sensor Shiled
DHW Sensor
RS485
DHW
33
SHUTDOWN
/SETBACK
35
37 38
PROVE
RS485
DHW
33
SHUTDOWN
/SETBACK
35
37 38
PROVE
Setback
Dry Contact
RS485
SHUTDOWN
/SETBACK
35
37 38
PROVE
Prove
Dry Contact
Shutdown
Dry Contact
Sensor Shiled
DHW Sensor
RS485
SHUTDOWN
/SETBACK
35
37 38
PROVE
RS485
DHW
SHUTDOWN
/SETBACK
35
37 38
PROVE
Setback
Dry Contact
RS485
SHUTDOWN
/SETBACK
35
37 38
PROVE
Setback
Dry Contact
Prove
Dry Contact
RS485
37 38
PROVE
RS485
37 38
PROVE
Setback
Dry Contact
Sensor Shiled
SENSORS MUST BE GOLD SERIES
SYSTEM
DHW
PUMP
17
RS485
19
Stage H
21
OUTDOOR
TEMP
27 29 31
DHW
33
SHUTDOWN
/SETBACK
35
RETURN
TEMP
20 22 28 30 32 34 3625 26
PRESS
+ -
37 38
PROVE
SYSTEM
TEMP
PROGRAM RUN
23 24
COMB.
AIR
DO NOT APPLY ANY VOLTAGE TO INPUT TERMINALS
Outdoor Sensor
Prove
Dry Contact
Sensor Shiled
DHW Sensor
System
Pump
DHW
Pump
Comb.
SENSORS MUST BE GOLD SERIES
SYSTEM
DHW
PUMP
17
RS485
19
Stage H
21
OUTDOOR
TEMP
27 29 31
DHW
33
SHUTDOWN
/SETBACK
35
RETURN
TEMP
20 22 28 30 32 34 3625 26
PRESS
+ -
37 38
PROVE
SYSTEM
TEMP
PROGRAM RUN
23 24
COMB.
AIR
DO NOT APPLY ANY VOLTAGE TO INPUT TERMINALS
SENSORS MUST BE GOLD SERIES
SYSTEM
DHW
PUMP
17
RS485
19
Stage H
21
OUTDOOR
TEMP
27 29 31
DHW
33
SHUTDOWN
/SETBACK
35
RETURN
TEMP
20 22 28 30 32 34 3625 26
PRESS
+ -
37 38
PROVE
SYSTEM
TEMP
PROGRAM RUN
23 24
COMB.
AIR
DO NOT APPLY ANY VOLTAGE TO INPUT TERMINALS
Setback
Dry Contact
WIRING THE DOMESTIC HOT WATER (DHW) SENSOR (TERMINALS 33, 34)
• DHW can be used to raise system Set Point to 200°F or Maximum Target, whichever is lower. DHW Piping
• DHW Call terminals can be either a dry contact N.O. or a temperature sensor that can be purchased separately
• If dry contact, wire an aquastat or other controls to provide closure on the DHW terminals.
• 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 DHW sensor to the S8 terminals marked
• Connect the shield to the circled terminal 34 with one of the sensor wires.
WIRING THE SHUTDOWN (TERMINALS 35, 36)
• This feature will only be available when Day/Night Schedules are selected as the Setback Mode option from the
• This feature can be used whenever it is desirable to turn off the S8 stage outputs from a remote location or
• When the Shutdown feature is enabled by closing a dry contact, all active stages will immediately turn off. The
• The Shutdown signal must be a dry contact only. No voltage can be placed across the
• Bring the two wires from the dry contact to the terminals marked SHUTDOWN- 35,36.
WIRING THE SETBACK (TERMINALS 35, 36)
• This feature can be used whenever it is desirable to switch the S8 to operate in Setback from a remote location
• When the Setback is enabled by closing a dry contact, the Target will change by the Setback value. That is, in
• The Setback signal must be a dry contact only. No voltage can be placed across the SETBACK terminals.
• Bring the two wires from the dry contact to the terminals marked SETBACK- 35,36.
WIRING THE PROVE (TERMINALS 37, 38)
• The Prove feature is provided to check system component operation before energizing the stages. It can be
• If the Comb. Air Damper Output option was not activated, the PROVE input can be used to check on the
• If the PROVE input is open on a call, the S8 will enable only the System Output. All stage outputs will be off
• A factory-installed jumper provides the System Prove signal. Do not remove the jumper unless it will be
• Bring the two wires from the dry contact to the terminals marked PROVE - 37, 38. No voltage can be placed
WIRING THE SYSTEM OUTPUT (TERMINALS 19, 20)
System Output Operation in Set Point Mode
• In Heating, the SYS output relay will energize whenever the outdoor temperature drops below the Outdoor
• No stage outputs will be activated until the Prove input is shorted. If a Prove is not required, the factory-
concept must be selected in the Startup Menu to determine the DHW Priority options.
(CA002400 or equivalent) for immersion in a 3/8ID well (CA002500 or equivalent).
DHW - 33, 34.
Startup menu.
another controller (i.e. EMS input).
System and Comb. Air, and unit pumps' or valves' relays will remain energized for the Run-On delay period and
then turn off.
SHUTDOWN terminals.
(i.e. EMS input or external time clock). It will only be available when External Signal are selected as the
Setback Mode option from the Startup menu.
Heating, the Target will be reduced by the Setback value. On the other hand, in Cooling, the Setback will be
added to the Target Set Point.
used to check on the Combustion Air Damper by connecting it to the end switch of the damper. In this case,
the Comb. Air Output option must be activated from the Startup Menu.
System Output. A typical use of this feature is to check for system pump flow before energizing any stage.
when the PROVE input is open.
replaced by a System Prove signal.
across the PROVE terminals
The PROVE input cannot be used as a safety limit. All equipment must have its own certified limit and safety
controls as required by local codes. No boiler stage will start unless Prove terminals are shorted. DO NOT remove
WARNING
the PROVE jumper supplied unless replacing it with a Prove signal.
Cutoff or whenever a stage output is active. If no outdoor sensor is connected and the last boiler relay has deenergized, the SYS relay will remain energized for a period set by the Run-On.
installed jumper should remain connected.
Page 11
LAARS Sequencing Controls S8 & S8EXT
DHW
Pump
SENSORS MUST BE GOLD SERIES
DHW
PUMP
RS485
21
OUTDOOR
TEMP
27 29 31
DHW
33
SHUTDOWN
/SETBACK
35
RETURN
TEMP
20 22 28 30 32 34 3625 26
PRESS
+ -
37 38
PROVE
SYSTEM
TEMP
23 24
COMB.
AIR
DO NOT APPLY ANY VOLTAGE TO INPUT TERMINALS
SENSORS MUST BE GOLD SERIES
SYSTEM
DHW
PUMP
RS485
19
21
OUTDOOR
TEMP
27 29 31
DHW
33
SHUTDOWN
/SETBACK
35
RETURN
TEMP
20 22 28 30 32 34 3625 26
PRESS
+ -
37 38
PROVE
SYSTEM
TEMP
PROGRAM RUN
23 24
COMB.
AIR
DO NOT APPLY ANY VOLTAGE TO INPUT TERMINALS
Setback
Dry Contact
Sensor Shiled
SENSORS MUST BE GOLD SERIES
RS485
OUTDOOR
TEMP
27 29 31
DHW
33
SHUTDOWN
/SETBACK
35
RETURN
TEMP
PRESS
+ -
37 38
PROVE
SYSTEM
TEMP
23 24
COMB.
AIR
DO NOT APPLY ANY VOLTAGE TO INPUT TERMINALS
Outdoor Sensor
Prove
Dry Contact
Shutdown
Dry Contact
Sensor Shiled
DHW Sensor
Comb.
Air
Damper
SENSORS MUST BE GOLD SERIES
RS485
OUTDOOR
TEMP
27 29 31
DHW
33
SHUTDOWN
/SETBACK
35
RETURN
TEMP
PRESS
+ -
37 38
PROVE
SYSTEM
TEMP
23 24
COMB.
AIR
DO NOT APPLY ANY VOLTAGE TO INPUT TERMINALS
SENSORS MUST BE GOLD SERIES
DHW
RS485
OUTDOOR
TEMP
27 29 31
DHW
33
SHUTDOWN
/SETBACK
35
RETURN
TEMP
PRESS
+ -
37 38
PROVE
SYSTEM
TEMP
23 24
COMB.
AIR
DO NOT APPLY ANY VOLTAGE TO INPUT TERMINALS
Setback
Dry Contact
Use Copper Conductors Only.
CAUTION:
Risk of Electric Shock.
SENSORS MUST BE GOLD SERIES
SYSTEM
3
DHW
PUMP
5
Stage A7Stage B9Stage C
11 13
Stage E15Stage F
17
Stage D
6 8 10 12 14
16 18
RS485
4
Stage G19Stage H
21
OUTDOOR
TEMP
27 29 31
DHW
33
SHUTDOWN
/SETBACK
35
RETURN
TEMP
20 22 28 30 32 34 3625 26
PRESS
+ -
37 38
PROVE
SYSTEM
TEMP
PROGRAM RUN
OUTPUT RATING: 6 AMP RESISTIVE, 1 AMP PILOT DUTY PER OUTPUT AT 120VAC.
23 24
COMB.
AIR
DO NOT APPLY ANY VOLTAGE TO INPUT TERMINALS
Setback
Dry Contact
Lo Hi
Unit1
Stages
Lo Hi
Unit2
Stages
Sensor Shiled
Use Copper Conductors Only.
CAUTION:
Risk of Electric Shock.
SENSORS MUST BE GOLD SERIES
SYSTEM
3
DHW
PUMP
5
Stage A7Stage B9Stage C
11 13
Stage E15Stage F
17
Stage D
6 8 10 12 14
16 18
RS485
4
Stage G19Stage H
21
OUTDOOR
TEMP
27 29 31
DHW
33
SHUTDOWN
/SETBACK
35
RETURN
TEMP
20 22 28 30 32 34 3625 26
PRESS
+ -
37 38
PROVE
SYSTEM
TEMP
PROGRAM RUN
OUTPUT RATING: 6 AMP RESISTIVE, 1 AMP PILOT DUTY PER OUTPUT AT 120VAC.
23 24
COMB.
AIR
DO NOT APPLY ANY VOLTAGE TO INPUT TERMINALS
Outdoor Sensor
Prove
Dry Contact
Sensor Shiled
System Sensor
Sensor Shiled
Return Sensor
Shutdown
Dry Contact
Sensor Shiled
DHW Sensor
Lo Hi
Unit1
Stages
Unit1
Pump
Lo Hi
Unit2
Stages
Unit2
Pump
System
Pump
DHW
Pump
Comb.
Air
Damper
Use Copper Conductors Only.
CAUTION:
Risk of Electric Shock.
SENSORS MUST BE GOLD SERIES
SYSTEM
3
DHW
PUMP
5
Stage A7Stage B9Stage C
11 13
Stage E15Stage F
17
Stage D
6 8 10 12 14
16 18
RS485
4
Stage G19Stage H
21
OUTDOOR
TEMP
27 29 31
DHW
33
SHUTDOWN
/SETBACK
35
RETURN
TEMP
20 22 28 30 32 34 3625 26
PRESS
+ -
37 38
PROVE
SYSTEM
TEMP
PROGRAM RUN
OUTPUT RATING: 6 AMP RESISTIVE, 1 AMP PILOT DUTY PER OUTPUT AT 120VAC.
23 24
COMB.
AIR
DO NOT APPLY ANY VOLTAGE TO INPUT TERMINALS
Use Copper Conductors Only.
CAUTION:
Risk of Electric Shock.
SENSORS MUST BE GOLD SERIES
SYSTEM
3
DHW
PUMP
5
Stage A7Stage B9Stage C
11 13
Stage E15Stage F
17
Stage D
6 8 10 12 14
16 18
RS485
4
Stage G19Stage H
21
OUTDOOR
TEMP
27 29 31
DHW
33
SHUTDOWN
/SETBACK
35
RETURN
TEMP
20 22 28 30 32 34 3625 26
PRESS
+ -
37 38
PROVE
SYSTEM
TEMP
PROGRAM RUN
OUTPUT RATING: 6 AMP RESISTIVE, 1 AMP PILOT DUTY PER OUTPUT AT 120VAC.
23 24
COMB.
AIR
DO NOT APPLY ANY VOLTAGE TO INPUT TERMINALS
Setback
Dry Contact
Lo Hi
Unit1
Stages
Lo Hi
Unit2
Stages
• In Cooling applications, the system relay will energize when the outdoor temperature is above the Outdoor Cutoff setting.
• 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/cool.
When stages are no longer required, the pump will stay active for an adjustable Run-On delay.
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 that acts as a dry contact only. It does not source any power.
• Class 1 voltages must enter the enclosure through a different opening from any Class 2 voltage wiring.
WIRING THE DHW PUMP (TERMINALS 21, 22)
The S8 can control the DHW Pump when the DHW Pump Output option is activated in the Startup Menu..
• The S8 will energize the DHW Pump whenever there is a call for DHW using a dry contact or when the DHW
temp falls below the DHW Set Point and DHW Differential.
• The DHW Pump output is Normally Open (N.O.) dry contact only. It does not source any power.
• Class 1 voltages must enter the enclosure through a different opening from any Class 2 voltage wiring.
WIRING THE COMBUSTION AIR DAMPER (TERMINALS 23, 24)
The S8 can control the Combustion Air Damper when the Comb. Air Output option is activated in the Startup
Menu.
• The S8 will energize the Combustion Air Damper relay whenever there is a call to energize any of the unit
stages.
• The Comb. Air output has one Normally Open (N.O.) dry contact relay. It does not source any power.
• Class 1 voltages must enter the enclosure through a different opening from any Class 2 voltage wiring.
• In this scenario, the Prove input will be used to check on the Combustion Air Damper status.
Page 11
WIRING THE STAGES (TERMINALS 3 TO 17)
The S8 can be configured to operate the stages of the heating or cooling units. Moreover, it can be
configured to operate the unit pumps or valves in addition to the unit stages.
• The N.O. contacts are dry contacts only. They do not source any voltage.
• 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.
WIRING THE STAGE OUTPUTS
• Each Stage output (A through H) has one Normally Open (N.O.) relay contact.
• When wiring several multi-stage units, start with the lower stage of the first unit and wire it to
Output A, followed by the higher stage of the same unit and wire it to Stage B.
WIRING THE PUMP OR VALVE OUTPUTS
• If the S8 is configured to operate Stage Pumps or Valves, then, wire them using the stage after the
highest stage for that unit. That is, the low stage for the first unit must be connected to A and the
higher stage of the same unit must be connected to Stage B. The Valve or Pump for the same unit
must be connected to Stage C.
Page 12
Page 12 LAARS Heating Systems
MENU SEQUENCE
STARTUP
SYS=168 F OD=45 F
TGT=172 F
ABC <EFG >
---- LO
BOILER MENU
------ SETTINGS ----- Season Winter
<Outdoor Rst> 135
Set Point 140
EMS Set Point 135
Min Return 110
<System Settings>
<Maintenance>
<System Startup>
BACK SELECT
MAINTENANCE
ARE YOU SURE?
No
Yes
BACK SAVE
---- CONTROL MODE ---
Outdoor Reset
Set Point
EMS 4-20mA
BACK SAVE
CAUTION
To be able to change the S8 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 padlock.
F
F
F
F
--- SENSOR FAULT -- Stages On
Stages Off
BACK SAVE
--- CONTROL LOGIC---
PID
OSS
BACK SAVE
---- DISPLAY UNIT -- F
C
BACK SAVE
EMS SET POINT
EMS 4mA SET POINT
100 F
[ ]
BACK SAVE
EMS 20mA SET POINT
170 F
[ ]
BACK SAVE
---- MAINTENANCE --- Unit F
Present Time 12:30P
<Sensor Trim>
<Histories>
<Configuration>
BACK SELECT
S8 V1.00
Outdoor reset
Heating-BreakOnRise
Day/Night Schedule
DHW Parallel
BACK SELECT
Sys=120 F 10:00AM
BACK NEXT
--- SENSOR TRIM --- System Trim +0 F
Outdoor Trim +0
Return Trim +0
DHW Trim +0
BACK SELECT
------ SEQUENCE ------ Lo/Hi/Lo/Hi
Lo/Lo/Hi/Hi
BACK SAVE
------ STAGING ----- Multiple Outputs
Single Output
BACK SAVE
-- TOTAL BOILERS --
8
[ ]
BACK SAVE
-- BOILER OUTPUT - None
Pump
Valve
BACK SAVE
--- BURNER TYPE ----
F
F
F
On/Off
2-Stage
3-Stage
4-Stage
BACK SAVE
---- APPLICATION -- Heat-BreakOnRise
Cool-MakeOnRise
BACK SAVE
---- DHW PIPING -- Parallel
Primary/Secondary
BACK SAVE
--DHW PUMP OUTPUT- No
Yes
BACK SAVE
--COMB. AIR OUTPUT- No
Yes
BACK SAVE
--- SETBACK MODE - Day/Night Schedule
External Signal
BACK SAVE
Page 13
LAARS Sequencing Controls S8 & S8EXT
Page 13
SET POINT
-- EMS SET POINT --
140 F
BACK SAVE
----- SET POINT ---- 140 F
[ ]
BACK SAVE
SYS=168 F OD=45 F
TGT=172 F
ABC <EFG >
---- LO
BOILER MENU
----- SETTINGS ------
Season Winter
<Outdoor Rst> 135
Set Point 140
EMS Set Point 135
Min Return 110
<System Settings>
<Maintenance>
<System Startup>
BACK SELECT
---- MIN RETURN --- 120 F
[ ]
BACK SAVE
---- RETURN LAG --- 2min
[ ]
BACK SAVE
- SYSTEM SETTINGS -
<Stage Settings>
<Setback Schedule>
<DHW Settings>
Setback 0
Run-On 2min
Pump Exercise Off
BACK SELECT
--- PUMP EXERCISE -Off
On
BACK SAVE
RESET RATIO
---- SEASON ---
Winter
Summer
BACK SAVE
-- OUTDOOR RESET Reset Ratio 7
Target Offset +0
Outdoor Cutoff 65
Min.Target 120
Max.Target 120
F
F
F
F
BACK SELECT
---- MAX TARGET ----
240 F
[ ]
BACK SAVE
---- MIN TARGET ----
120 F
[ ]
BACK SAVE
F
F
F
F
-- OUTDOOR CUTOFF - 70 F
[ ]
BACK SAVE
-- TARGET OFFSET -- +0 F
[
]
BACK SAVE
---- RESET RATIO -- Custom
1(8.00
2(4.00
3(3.00
4(2.00
5(1.50
6(1.25
7(1.00 OD:1.00 SYS)
8(1.00
9(1.00
10(1.00
11(1.00
12(1.00
OD:1.00 SYS)
OD:1.00 SYS)
OD:1.00 SYS)
OD:1.00 SYS)
OD:1.00 SYS)
OD:1.00 SYS)
OD:1.25 SYS)
OD:1.50 SYS)
OD:2.00 SYS)
OD:3.00 SYS)
OD:4.00 SYS)
BACK SAVE
-- SET SYS TEMP.1 100 F
[
]
BACK SAVE
-- AT OD TEMP.1 -- 70 F
[ ]
BACK SAVE
-- SET SYS TEMP.2 170 F
[
]
BACK SAVE
-- AT OD TEMP.2 -- 0 F
[ ]
BACK SAVE
DHW SETTINGS
DHW PRIORITY TIMER
2min
-- DHW SETTINGS -- DHW Temp. 120 F
DHW Prior Tmr 60min
DHW Set Point 120
DHW Diff. 5
F
F
BACK SELECT
F
------ SETBACK -------
0 F
[ ]
BACK SAVE
------- RUN-ON -------
2min
[ ]
BACK SAVE
[ ]
BACK SAVE
-- DHW SET POINT - 120 F
[ ]
BACK SAVE
DHW DIFFERENTIAL
10 F
[ ]
BACK SAVE
Page 14
Page 14 LAARS Heating Systems
STAGE SETTINGS
- SYSTEM SETTINGS <Stage Settings>
<Setback Schedule>
<DHW Settings>
Setback 0
Run-On 2min
Pump Exercise Off
BACK SELECT
----- SETTINGS ----- Season Winter
<Outdoor Rst> 135
Set Point 135
EMS Set Point 135
Min Return 110
<System Settings>
<Maintenance>
<System Startup>
BACK SELECT
-- STAGE SETTINGS - Reaction Time 1min
Purge Delay 0.0min
Min Runtime 2min
F
F
F
F
F
Standby Delay 10min
Last Stage Hold 5
Throttle 2
<Lead Settings>
BACK SELECT
-- LEAD SETTINGS - Lead Boiler AB
Rotate Mode Time
BACK SELECT
-- LEAD ROTATION - Time
Manual
FOFO
BACK SELECT
AUTO ROTATE PERIOD
24hrs
[ ]
BACK SAVE
F
F
-- REACTION TIME - 2min
[ ]
BACK SAVE
--- PURGE DELAY ----
0.0min
[ ]
BACK SAVE
- MINIMUM RUNTIME 2min
[ ]
BACK SAVE
-- STANDBY DELAY - 10min
[ ]
BACK SAVE
LAST STAGE HOLD
0 F
[ ]
BACK SAVE
SCHEDULES
SETBACK SCHEDULE
Setback 0 F
Present Time **:**
Day Schdul 7:00Am
Night Schdul 7:00Pm
BACK SELECT
-- NIGHT SCHEDULE --
07:**Pm
BACK SAVE
-- DAY SCHEDULE ----
07:**Am
BACK SAVE
- SET PRESENT TIME
**:**
BACK SAVE
-- LEAD BOILER - AB
CD
BACK SELECT
SYS=168 F OD=45 F
TGT=172 F
ABC <EFG >
---- LO
BOILER MENU
------ BOOST PERIOD-- 30min
[ ]
BACK SAVE
-- THROTTLE RANGE - 2 F
[ ]
BACK SAVE
STAGE MENU
-- BOILER AB MODE Auto
Standby
Off
On
BACK SAVE
----- BOILER AB ---- Mode Auto
Runtime 58Hrs
<Prev Boiler>
<Next Boiler>
BACK SAVE
------ SETBACK ------ 0 F
[ ]
BACK SAVE
-------- BOOST -------- 0 F
[ ]
BACK SAVE
BOILER AB RUNTIME
58hrs
BACK CLEAR OK
Page 15
LAARS Sequencing Controls S8 & S8EXT
O
P
Power
EXTENSION
MODULE
RS-485
Ext A
INPUT RATINGS:
115VAC 60Hz, 12VA MAX
OUTPUT RATINGS:
120VAC, 6A RESISTIVE
1A PILOT DUTY, 15A TOTAL
FOR ALL CIRCUITS
Ext B
W
X
O
P
Power
EXTENSION
Ext A
INPUT RATINGS:
115VAC 60Hz, 12VA MAX
OUTPUT RATINGS:
120VAC, 6A RESISTIVE
1A PILOT DUTY, 15A TOTAL
FOR ALL CIRCUITS
Ext B
W
X
S8EXT
SEQUENCING CONTROL
Connecting S8 to Two Extension Panels
and XSIG Interface using RS485
S8
SYSTEM
DHW PUMP
INPUT RATINGS:
115VAC 60Hz, 12VA MAX
Use Copper Conductors Only.
CAUTION:
Risk of Electric Shock.
PWR
L N
1 2
SENSORS MUST BE GOLD SERIES
SYSTEM
3
DHW
PUMP
5
Stage A7Stage B9Stage C
11
13
Stage E15Stage F
17
Stage D
6 8 10 12 14
16 18
RS485
SYS=144F OD=35F
<AB
> DE GH JK
HI LO -- OFF
4
Stage G19Stage H
21
OUTDOOR
TEMP
27 29
31
DHW
33
SHUTDOWN
/SETBACK
35
RETURN
TEMP
20 22 28 30 32 34 36
STAGE MENU
Stage E
Stage F
Stage G
Stage H
Stage A
Stage B
Stage C
Stage D
25
26
PRESS
+ -
37
38
PROVE
SYSTEM
TEMP
PROGRAM RUN
23 24
COMB.
AIR
DO NOT APPLY ANY VOLTAGE TO INPUT TERMINALS
COMB. AIR
ENCLOSED
ENERGY
MANAGEMENT
EQUIPMENT
LISTED
99RA
C US
O
P
Power
CAUTION:
Risk of Electric Shock.
PWR
L N
1 2I3 4J5 6K7 8L9 10
M
11 12
EXTENSION
MODULE
RS-485
Ext A
INPUT RATINGS:
115VAC 60Hz, 12VA MAX
OUTPUT RATINGS:
120VAC, 6A RESISTIVE
1A PILOT DUTY, 15A TOTAL
FOR ALL CIRCUITS
Ext B
L
M
N
Comm
T
U
V
W
X
N
13 14
Q
S
U
R
T
V
S8EXT A
Use Copper Conductors Only.
I
J
K
Q
R
S
O
15 16P17 18
W
X
O
P
Power
CAUTION:
Risk of Electric Shock.
PWR
L N
1 2I3 4J5 6K7 8L9 10
M
11 12
EXTENSION
MODULE
RS-485
Ext A
INPUT RATINGS:
115VAC 60Hz, 12VA MAX
OUTPUT RATINGS:
120VAC, 6A RESISTIVE
1A PILOT DUTY, 15A TOTAL
FOR ALL CIRCUITS
Ext B
L
M
N
Comm
T
U
V
W
X
N
13 14
Q
S
U
R
T
V
S8EXT B
Use Copper Conductors Only.
I
J
K
Q
R
S
O
15 16P17 18
W
X
4-20 mA EMS
4-20mA INPUT
+
Signal GND
1
2
3
RS485
EXTENSION
CONNECTORS
XSIG 4-20mA EMS Interface
4-20mA
EMS Signal
(+)
(-)
6 Pin Phone Cable (provided with Extension)
6 Pin Phone Cable (provided with XSIG Interface)
S8
SEQUENCING CONTROL
S8EXT
SEQUENCING CONTROL
XSIG
CONNECTING TO THE S8EXT PANELS AND XSIG INTERFACE
• The S8 is equipped with a 6-pin phone socket to connect to S8EXT panels or XSIG Interface.
• Only 6-wire phone cable provided must be used for proper operation.
• Each S8 Extension has two RS485 communication ports. Use one to connect to the S8. Use the other port to connect to the
second extension or XSIG Interface.
• Additional compatible devices can utilize the second RS485 connection on the second S8 Extension. i.e. XSIG Interface
(CA004200) to provide a 4-20mA set point signal to the S8.
Page 15
SELECTING THE S8EXT PANEL LETTER
• The S8 is capable of communicating to two S8EXTs. However, each extension must be identified
as either A or B using the switch on each extension to avoid having communication problem.
• Extension A (Switch is set to "A") will operate stages "I" through "P". While Extension B
(Switch is set to "B") will operate stages "Q" through "X".
Page 16
Page 16 LAARS Heating Systems
and XSIG Interface using RS485
S8
SYSTEM
DHW PUMP
SENSORS MUST BE GOLD SERIES
SYS=144F OD=35F
<AB
> DE GH JK
HI LO -- OFF
STAGE MENU
SYSTEM
PROGRAM RUN
DO NOT APPLY ANY VOLTAGE TO INPUT TERMINALS
COMB. AIR
C US
CAUTION:
Risk of Electric Shock.
Use Copper Conductors Only.
I
J
K
Q
R
S
S8
SEQUENCING CONTROL
STARTUP SETTINGS
A good practice after performing any Startup menu modifications is to
check all operating settings and adjustments to match the new settings.
CAUTION
PROGRAM CHANGE SETTINGS
To be able to change the S8 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 padlock.
STARTUP SEQUENCE
Button: MENU/<System Startup>
• When powered, the S8 performs a self-test on its components. After the self-test
diagnostics have been successfully completed, the S8 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 S8 has already been configured.
• The System Startup menu sets the main parameters like the type of sensor, the type of output whether heating or cooling, the
sequencing mode, and many other parameters described in this section.
• Before entering the Startup menu, several warnings will alert you about the consequences of making Startup changes.
CONTROL MODE
Outdoor Reset, Set Point, EMS 4-20mA Default: Set Point
Button: MENU/<System Startup>/..../Control Mode
• Outdoor Reset provides a variable set point based on outdoor temperature. Available for
Heating applications only.
• Outdoor Reset mode requires the use of an outdoor sensor. DO NOT select Reset without
an outdoor sensor.
• 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 stages, system, and Comb. Air relays off.
• The EMS 4-20mA allows the S8 to receive an external set point from an EMS/BMS system. This option requires the use of the
XSIG Interface (CA004200).
• You must select the 4mA (min) and 20 mA (max) Set Points in the following screens.
• Connect the XSIG Interface to the S8's RS485 connection.
ARE YOU SURE?
No
Yes
BACK
---- CONTROL MODE ---
Outdoor Reset
Set Point
EMS 4-20mA
BACK
SAVE
SAVE
DISPLAY UNIT
ºF, ºC Default:ºF
Button: MENU/<System Startup>/..../Display Unit
• The S8 is designed to control boilers and chillers in hydronic environment where the
temperature is the critical factor. It allows the user of displaying temperature information
and settings in either ºF (Fahrenheit) or ºC (Celsius). Select the display unit that is best
suited for your application.
SETTING THE 4MA AND 20MA SET POINTS (AVAILABLE IN 4-20MA EMS ONLY)
Default: Normal
Button: MENU/<System Startup>/..../EMS 4mA Set Point/EMS 20mA Set Point
• If EMS 4-20mA is selected from the Control Mode Menu as the temperature set point
source, the user must purchase a Laars XSIG Interface (CA004200) to accept the 420mA signal and transmit it to the S8.
• In addition, the user will need to set the temperature range parameters. First, set the 4mA
temperature, then the 20mA temperature.
• Any signal that is above or below the 4-20mA range will display the message
"Shutdown by EMS" and all stages will de-energize. However, the System,
Comb. Air, and Unit Pumps and Valves will continue for the Run-On delay period then
de-energize.
• The control will calculate the temperature for the additional 1.9mA at each end of 4
- 20mA range.
---- DISPLAY UNIT --F
C
BACK
EMS 4mA SET POINT
100
[ ]
BACK
EMS 20mA SET POINT
170
[ ]
BACK
SAVE
F
SAVE
F
SAVE
Page 17
LAARS Sequencing Controls S8 & S8EXT
Page 17
APPLICATION
Heating-BreakOnRise, Cooling-MakeOnRise Default: Heating-BreakOnRise
Button: MENU/<System Startup>/..../Application
• The S8 offers two application modes, Heating and Cooling. In Heating, the S8 will
sequence stages and when the system temperature is below the set point. In addition,
the system relay will energize when the outdoor temperature is at or below the Outdoor
Cutoff setting.
• In Cooling, the S8 will sequence stages and when the system temperature is above the set point. In addition, the system relay
will energize when the outdoor temperature is at or above the Outdoor Cutoff setting.
• No Return Temperature monitoring or DHW options will be available in cooling applications.
DHW PIPING (AVAILABLE WITH HEATING ONLY)
Parallel, Primary/Secondary Default: Parallel
Button: MENU/<System Startup>/..../DHW Piping
• When Parallel is selected, the S8 will offer a DHW Priority Timer. The DHW Priority
will only take place during heating periods.
• The Parallel option will allow the DHW Pump relay to energize while de-energizing the
System relay when there is a DHW call during heating. However, during Summer, only
the DHW Pump relay will energize on a DHW call.
• Selecting the Primary/Secondary option will energize the System relay with the DHW Pump relay whenever there is a call for
DHW even during the Summer or when outdoor temperature is above the Outdoor Cutoff.
---- APPLICATION -- Heat-BreakOnRise
Cool-MakeOnRise
SAVE
BACK
---- DHW PIPING -- Parallel
Primary/Secondary
BACK
SAVE
IMPORTANT
A DHW call can be initiated by either a dry contact or using a Laars Sensor (CA002400 or
equivalent) for immersion in a 3/8ID well (CA002500 or equivalent). The use of a sensor will allow
the adjustment of DHW Set Point and DHW Differential.
DHW PUMP OUTPUT
No, Yes Default: No
Button: MENU/<System Startup>/..../DHW Pump Output
• The S8 can control the operation of the DHW Pump. This option allows the user to
select if the S8 should be controlling the DHW Pump or not.
COMBUSTION AIR DAMPER OUTPUT
No, Yes Default: No
Button: MENU/<System Startup>/..../Comb. Air Output
• The S8 can control the operation of the Combustion Air Damper. This option allows the
user to select if the S8 should be controlling the Combustion Air Damper or not.
• If Yes is selected, the S8 will energize the Comb. Air relay whenever there is a call for a boiler and will use the Prove input to
check on the status of the Combustion Air Damper. In a failure situation, the message "
will display when there is a call for a boiler stage until Prove is Shorted.
• If Prove fails after boiler stages where energized, the stages will de-energize and the message "
Failure" will display until situation is rectified.
• If No is selected, the Prove input will be used to check System status instead of the Combustion Air Damper.
SETBACK MODE
Day/Night Schedules, External Signal Default: Day/Night Schedules
Button: MENU/<System Startup>/..../Setback Mode
• The S8 can either utilize its built-in day schedule or an external dry contact signal to
switch to Setback.
• If Day/Night Schedules is selected, The Setback will follow the Day/Night Schedule and Shutdown/Setback input (terminals 35
and 36) will be used as Shutdown only.
• The External Signal will allow the Shutdown/Setback input (terminals 35 and 36) to work as an input for Setback. No
Shutdown input will be available in this scenario.
--DHW PUMP OUTPUT- No
Yes
BACK
- COMB. AIR OUTPUT No
Yes
BACK
Wait for Comb. Prove"
Comb. Prove
--- SETBACK MODE - Day/Night Schedule
External Signal
BACK
SAVE
SAVE
SAVE
Page 18
Page 18 LAARS Heating Systems
BURNER TYPE
On/Off, 2-Stage, 3-Stage, 4-Stage Default: On/Off
Button: MENU/<System Startup>/..../Burner Type
• The S8 can sequence from a single stage and up to four stages per heating or cooling
unit.
BOILER OUTPUT
None, Pump, Valve Default: None
Button: MENU/<System Startup>/..../Boiler Output
• When None is selected, the S8 will sequence multiple heating or cooling units without
any additional unit pumps or valves.
• The Pump option allows the S8 to control the cooling or heating unit stages in addition
to the unit pumps. The stage pump will run for the Run-On delay after the lower stage of
that unit has de-energized.
• The Valve optional functions similar to the pump option except that when all stages are off and after Run-On delay has elapsed,
the Lead unit's valve relay will remain energized to allow for pump flow across the system. The lead unit's valve will remain
energized until the Outdoor temperature rises above the Outdoor Cutoff or when the Shutdown, or Summer is activated.
TOTAL BOILERS
1 to 24 Default: varies based on Burner Type and Boiler Output
Button: MENU/<System Startup>/..../Boiler Output
• This option in combination with Burner Type and Boiler Output Startup options will
determine the total number of outputs the S8 will need to control.
• If more stages are selected than the S8 and S8 Extension has, the extra stages will have
CE as their status.
--- BURNER TYPE --- On/Off
2-Stage
3-Stage
4-Stage
BACK
-- BOILER OUTPUT --
None
Pump
Valve
BACK
-- TOTAL BOILERS - 8
[ ]
BACK
SAVE
SAVE
SAVE
STAGING
Multiple Outputs, Single Output Default: Multiple Outputs
Button: MENU/<System Startup>/..../Staging
• Most units will require that the higher output stages to be energized after the lower output
stages. These units will need to select the Multiple Output option. That means, both
Low and High Output stages must be energized for the unit to function.
• Some units require that when the higher output stages are required, the lower stages must
de-energize. To operate these units, the user must select the Single Output option.
SEQUENCE
Lo/Hi/Lo/Hi, Lo/Lo/Hi/Hi Default: Lo/Hi/Lo/Hi
Button: MENU/<System Startup>/..../Sequencing
• Some units run more efficient when the lower stages are energized alone than with
the higher stages. These types of units should select Lo/Lo/Hi/Hi. Then, the S8 will
sequence the lower stages of all Automatic units before sequencing the higher stages.
• For
stage of the same unit. Then when more stages are needed, it will fire the lower stage of the lag unit followed by the higher
stage of the lag unit.
CONTROL LOGIC
PID, OSS (Over-Sized-System) Default: PID
Button: MENU/<System Startup>/..../Sequencing
• The PID option allows the S8 to sequence stages based on Reaction Time and Boiler Min
Run Time. The PID relies on the rate of change in the System Temperature. The PID
logarithmic calculations foresee changes and sequence stages based on those changes. It
is the most efficient operation for most heating and cooling applications.
------ STAGING ----- Multiple Outputs
Single Output
BACK
------ SEQUENCE ------ Lo/Hi/Lo/Hi
Lo/Lo/Hi/Hi
BACK
--- CONTROL LOGIC---
PID
OSS
BACK
SAVE
SAVE
SAVE
Page 19
LAARS Sequencing Controls S8 & S8EXT
• The Oversize option sequence stages based on how many Throttling ranges (differentials) is the system temperature away
from the Target Temperature. In Heating and at one Throttling range below the Set Point, only one stage will be on. For
each additional Throttling range below the Set Point, an additional stage will be activated. The last stage on will be allowed
to exceed the Set Point by one Throttling range before turning off that stage. This helps to prevent the last stage from short
cycling.
When PID is Selected, the following are the settings that directly affects this modes operation:
• Reaction Time SELECT Settings/System Settings/Stage Settings/Reaction Time
• Purge Delay SELECT Settings/System Settings/Stage Settings/Purge Delay
• Minimum Run Time SELECT Settings/System Settings/Stage Settings/Min Runtime
• Standby Delay SELECT Settings/System Settings/Stage Settings/Standby Delay
• Last Stage Hold SELECT Settings/System Settings/Stage Settings/Last Stage Hold
When Oversize (OSS) is Selected, the following are the settings that directly affects this modes operation:
• Throttle SELECT Settings/System Settings/Stage Settings/Throttle
Page 19
SENSOR FAULT
Stages On, Stages Off Default: Stages 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.
RESET MODE
• When Stages-On is selected, the S8 will turn all unit stages On when the System reads Short or Open and Outdoor is below
Outdoor Cutoff in heating or above Outdoor Cutoff in Cooling. When Outdoor reads Short or Open, the S8 will change the
Target to me the Maximum Target.
• When Stages-Off is selected, the S8 will turn all stages Off when the System reads Short or Open. However, when the Outdoor
reads Short or Open, the S8 will change the Target to me the Minimum Target.
SET POINT MODE
• When Stages-On is selected, the S8 will turn all stages On when the System sensor reads Short or Open.
• When Stages-Off is selected, the S8 will turn all stages 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.
--- SENSOR FAULT -- Stages On
Stages Off
BACK
SAVE
Page 20
Page 20 LAARS Heating Systems
and XSIG Interface using RS485
S8
SYSTEM
DHW PUMP
SENSORS MUST BE GOLD SERIES
SYS=144F OD=35F
<AB
> DE GH JK
HI LO -- OFF
STAGE MENU
SYSTEM
PROGRAM RUN
DO NOT APPLY ANY VOLTAGE TO INPUT TERMINALS
COMB. AIR
C US
CAUTION:
Risk of Electric Shock.
Use Copper Conductors Only.
I
J
K
Q
R
S
S8
SEQUENCING CONTROL
Outdoor Temperature
Wate r Temperature
70 405060
130
120
110
100
Outdoor Temperature
Wate r T empe ratur e
70 405060
110
100
90
80
Outdoor Temperature
Wat er Temper ature
70 405060
150
140
130
120
1:4
With a 0° Offset, the
ratio curves begin at
100° WaterTemperature.
With a -20° Offset, the
ratio curves begin at
80° WaterTemperature.
With a +20° Offset, the
ratio curves begin at
120° WaterTemperature.
1:4
1:4
1:1
1:1
1:1
4:1
4:1
4:1
90
100
+20 Offset
-20 Offset
Outdoor Temperature
Wate r Temperature
70 405060
130
120
110
100
1:4
1:1
4:1
Colder
Warmer
OPERATING SETTINGS
PROGRAM CHANGE SETTINGS
To be able to change the S8 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 padlock.
SEASON
Winter, Summer Default: Winter
Button: MENU/Season
• When in Summer, and in Heating Mode, the S8 will turn all boiler relays off. However,
a DHW call will bring boilers back on if needed. The Message Display Line will display
Summer. On ther other hand, in Cooling Mode, the S8 will turn all boiler relays off
when it is in Winter setting. The Message Display Line will show Winter.
DO NOT turn power off to the S8
when in off-season or season is
over. If you do so, the battery
will run down and will have to
be replaced. Instead switch to
Summer or Winter.
CAUTION
• When in Winter, the S8 will activate the Sys relay whenever the Outdoor temperature
falls to or below the Outdoor Cutoff setting in heating applications. In addition, it will
begin heating whenever the System temperature falls below the Set Point Temperature.
The Message Display Line will not display any season information. However, in
Cooling , all stages will be off and the Message Display Line will display
Winter.
• When the season is over, it is a good practice to switch the S8 Season setting. This will
---- SEASON ---
Winter
Summer
BACK
SAVE
allow DHW calls in heating to operate the boilers when needed.
RESET RATIO
Custom, 1(8.00ºOD : 1.00ºSys) to 12 (4.00ºOD : 1.00ºSys) Default: 1(1.00ºOD : 1.00ºSys)
Button: MENU/<Outdoor Reset>/Reset Ratio In Outdoor Reset Only
• The Reset Ratio applies only to Heating applications.
• The Reset Ratio determines how the System water temperature will vary with Outside
temperature. With any of the ratios, the colder it becomes outside, the hotter the
temperature of the system water. (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 35°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
will only be 125°F, and at 22°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
---- RESET RATIO -- Custom
1(8.00
2(4.00
3(3.00
4(2.00
5(1.50
6(1.25
7(1.00
8(1.00
9(1.00
10(1.00
11(1.00
12(1.00
BACK
OD:1.00 SYS)
OD:1.00
OD:1.00 SYS)
OD:1.00
OD:1.00 SYS)
OD:1.00
OD:1.00
OD:1.25 SYS)
OD:1.50
OD:2.00
OD:3.00
OD:4.00
SYS)
SYS)
SYS)
SYS)
SYS)
SYS)
SYS)
SYS)
SAVE
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).
CUSTOMIZED RESET RATIO
Button: MENU/<Outdoor Reset>/Reset Ratio/Custom
• F
can be used.
• The Custom Reset Ratio is only available when Custom is selected from the Reset Ratio menu option. It provides the user
with the capability of assigning two points on the reset ratio diagram and use the line that connects those two points as the
customized reset ratio curve. Each of the two points will need a specific System and Outdoor Temperature to identify it on the
diagram.
Page 21
LAARS Sequencing Controls S8 & S8EXT
Outdoor Temperature (in °F)
70 60 50 40 2030 0 -1010 -20
120
140
130
150
160
170
180
100
110
Water Temperature (in °F)
Custom Reset Ratio
Point1: System=120°F
Oudoor=60°F
Point2: System=170°F
Oudoor=0°F
Point1
Point2
Customized Reset Ratio
Max Target
Min Target
Page 21
• To Set the first point, specify Sys Temp 1, and OD Temp 1. Then, specify Sys Temp 2, and OD Temp 2, to set the second point
on the curve. The two points can be anywhere on the line, not necessarily at the ends.
• The chart shows an example of a customized curve 6(OD):5(SYS) that does not exist in the standard curve options. If the
outdoor temperature reaches 30ºF, the system target will be 145ºF.
• Remember that the Min Target and Max Target apply to all reset ratios including the customized reset ratio ones.
-- SET SYS TEMP.1 -
120
F
[
]
BACK
SAVE
-- AT OD TEMP.1 ---
60
F
[ ]
BACK
SAVE
SET POINT (NOT ADJUSTABLE IN EMS MODE)
Adjustable -10ºF/-23ºC - 230ºF/110ºC Default: 140ºF/60ºC
Button: MENU/Set Point In Set Point or EMS 4-20mA
• The Set point is the temperature value the S8 will use to control the system.
-- SET SYS TEMP.2 -
170
F
[
]
BACK
SAVE
-- AT OD TEMP.2 ---
0
F
[ ]
BACK
SAVE
----- SET POINT -----
70
F
[ ]
BACK
SAVE
• The S8 will add, subtract, or hold the stages of the heating or cooling units 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 System Settings and
Stage Settings.
• If an Outdoor Sensor was connected, pressing the SAVE button will switch to the Outdoor Cutoff setting option.
• If the EMS Mode was Enabled, the Set Point will be set by the EMS/BMS system and will be available to be only read.
• The range of Set Point in the EMS is set in the Startup menu at 4mA and 20mA.
• Any reading below the 2mA or above 22mA will indicate a "Shutdown by EMS" message on the Message Line.
OUTDOOR CUTOFF TEMPERATURE
Adjustable Off, 20ºF/-7ºC - 100ºF/38ºC, On Default: 70ºF/21ºC
Button: MENU/Set Point/Outdoor Cutoff in Set Point
Button: MENU/<Outdoor Reset>/Outdoor Cutoff in Reset
-- OUTDOOR CUTOFF --
70
F
[ ]
BACK
SAVE
• In Outdoor Reset mode, Outdoor Cutoff will always exist. However, in Set Point mode,
if the outdoor sensor is installed, the Outdoor Cutoff screen will automatically appear
after the temperature Set Point has been selected.
• In Heating applications, when the outdoor temperature falls to the adjustable Outdoor Cutoff temperature, the S8 will control
and sequence the boiler stages to hold the calculated temperature.
• When the outdoor temperature rises to the Outdoor Cutoff plus a 2°F differential, the S8 will turn all boilers off. The System
relay and any other Pump or valve relays that were energized will remain energized for the Run-On delay.
• In Cooling applications, when the outdoor temperature rises to the adjustable Outdoor Cutoff temperature, the S8 will control
and sequence the cooling unit stages to hold the calculated temperature.
• The Outdoor Cutoff can be set to ON or OFF. In the ON position, the System Relay will run regardless of the Outdoor
temperature and the burner stages will be active to hold the calculated water temperature.
• In the OFF position, the system pump will always be off and all stages will be off as well.
TARGET OFFSET
Adjustable from 40ºF/22ºC - (-40ºF/-22ºC) Default: 0ºF/0ºC
Button: MENU/<Outdoor Reset>/Offset in Outdoor Reset only
• The Offset setting lets you adjust the starting points of the Reset Ratio curves. This
means that, regardless of the Outdoor temperature, 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.
-- TARGET OFFSET ---
+0
F
[
]
BACK
SAVE
Page 22
Page 22 LAARS Heating Systems
• The Offset setting does not change the ratio selection. For instance, with 1.00 (OD):1.00 (SYS) Reset Ratio, the System water
temperature will always increase one degree for each degree change in the Outdoor temperature. What the Offset does is add or
subtract a constant temperature value. (See Understanding Operation Concept on page 5)
• The Minimum and Maximum Target will take precedence over the Offset. That is, if the Max Target was set to 180°F and the
Offset was set to 20°F. If the set point was 170°F, the new calculated set point based with the Offset will not exceed 180°F.
• If required: Adjust the Water Offset in mild weather. If the ambient building temperatures are too warm in the mild
weather, decrease the Target Offset. If the ambient building temperatures are too cold in the mild weather, increase the Target
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.
MINIMUM TARGET
Adjustable 70ºF/21ºC - 180ºF/82ºC Default: 120ºF/49ºC
Button: MENU/<Outdoor Reset>/Min. Target in Outdoor Reset only
• The Minimum Target must be set to the boiler manufacturer’s specification. The S8 will
calculate the Set Point based on the Outdoor temperature, the Reset Ratio, and the Offset
value. The S8 will control all boilers to hold either the Set Point
temperature, or the Minimum Target, whichever is higher.
• The Minimum Target must be at least 20°F lower than the Maximum Target (See next setting).
MAXIMUM TARGET
Adjustable 90ºF/32ºC - 240ºF/116ºC Default: 240ºF/116ºC
Button: MENU/<Outdoor Reset>/Max. Target in Outdoor Reset only
• This is the highest temperature heating water the S8 will circulate through the heating
system.
• When using a radiation system, it should be set according to the tubing or floor manufacturer’s specification.
• The Maximum Target must be at least 20°F higher than the Minimum Target (See previous setting)..
---- MIN TARGET --- 120
[ ]
BACK
---- MAX TARGET --- 240
[ ]
BACK
F
SAVE
F
SAVE
BOILER MINIMUM RETURN
Wh
monitoring the Target temperature (TGT), System temperature (SYS), Minimum Return, and actual return. (RTN). When the S8
predicts that a low return will occur, it will increase the Target automatically as an effort to increase the return temperature.
MINIMUM RETURN
Adjustable Off, 80ºF/27ºC - 140ºF/60ºC Default: 120ºF/49ºC
Button: MENU/Min. Return in Heating only
• The Minimum Return is the critical temperature at which the return should be above.
Normally, this setting is provided by the boiler manufacturer or the system engineer.
• The S8 will use that value as a guide. It will start to add additional stages if it foresees that the RTN temperature will drop
below the Min. Return. During that period, it will display "Hold Return at 120
indicate that the S8 is sequencing boilers to protect the return from dropping below the Minimum Return.
• Most condensing boilers will run more efficient with cooler return temperatures. In this case, select the Off option on the
Minimum Return to allow the monitoring of the return on the display without sequencing the boiler stages.
RETURN LAG
Adjustable 0 - 30 minutes Default: 2 minutes
Button: MENU/Min. Return/Return Lag in Heating only
• The Return Lag is the time it takes for the system return to change after sequencing the
stages.
• To get this time, start from a cold system. Calculate the amount of time it takes to get the
return five degrees warmer from the start of the boiler. That should be your Return Lag.
---- MIN RETURN --- 120
[ ]
BACK
F" in the Display Message Line to
---- RETURN LAG --- 2min
[ ]
BACK SAVE
F
SAVE
Page 23
LAARS Sequencing Controls S8 & S8EXT
and XSIG Interface using RS485
S8
SYSTEM
DHW PUMP
SENSORS MUST BE GOLD SERIES
SYS=144F OD=35F
<AB
> DE GH JK
HI LO -- OFF
STAGE MENU
SYSTEM
PROGRAM RUN
DO NOT APPLY ANY VOLTAGE TO INPUT TERMINALS
COMB. AIR
C US
CAUTION:
Risk of Electric Shock.
Use Copper Conductors Only.
I
J
K
Q
R
S
S8
SEQUENCING CONTROL
Page 23
SYSTEM SETTINGS
Button: MENU/<System Settings>
The System Settings menu provide access to adjusting and fine-tuning the system for enhanced
comfort and better fuel savings. The S8 behaves differently based on the selected Control
Modes (see Startup Settings).
PROGRAM CHANGE SETTINGS
To be able to change the S8 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 padlock.
STAGE SETTINGS
Button: MENU/<System Settings>/<Stage Settings>
REACTION TIME
Adjustable 1 - 10 minutes Default: 2 minutes
Button: MENU/<System Settings>/<Stage Settings>/Reaction Time in PID Logic only
• It is the amount of time it takes a single stage to affect the system.
• After the S8 turns on a stage trying to meet a set point, it will not turn on another stage
until the reaction time has elapsed. Then, it will recalculate if a stage is need.
• To determine the optimum time, in a heating system start with a hot system. However,
in a cooling system start with a cool system. Then, turn on a single stage and calculate
how long it takes until the system begins to respond to that stage. That period should be
set as the Reaction Time.
- SYSTEM SETTINGS -
BACK
-- STAGE SETTINGS --
BACK
-- REACTION TIME --
2min
BACK
SELECT
SELECT
SAVE
PURGE DELAY
Adjustable 0.0 - 10.0 minutes Default: 0.0 minutes
Button: MENU/<System Settings>/<Stage Settings>/Purge Delay in PID Logic only
• Most large units must go through a purge cycle before they are brought on line.
• When the S8 activates a unit (the lowest stage on a unit), it does not start to calculate
its output until the Purge Delay is over. This allows the unit to fully come on line and to
begin producing output.
• The Purge Delay helps to prevent short cycling of a newly activated units. Once the lowest unit stage 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 units manufacturer specification.
MINIMUM RUNTIME
Adjustable 1 - 60 minutes Default: 2 minutes
Button: MENU/<System Settings>/<Stage Settings>/Min Runtime in PID Logic only
• This is the minimum amount of time any stage will run.
• For the lowest stage of a unit, the Minimum Runtime starts after the purge cycle.
• Initially, set the Min Runtime to half the Reaction Time.
• If System tends to overshoot, reduce the Min Runtime. If boilers tends to short cycle, increase Min Runtime.
STANDBY DELAY
Adjustable 1 - 60 minutes Default: 10 minutes
Button: MENU/<System Settings>/<Stage Settings>/Standby Delay in PID Logic only
• The Standby Delay Time only applies to units in Standby Mode.
• A Standby unit can only be activated after all the units in Auto Mode have run for the
full Standby Time.
--- PURGE DELAY ----
0.0min
[ ]
SAVE
BACK
- MINIMUM RUNTIME 2min
[ ]
BACK
-- STANDBY DELAY - 10min
[ ]
BACK
SAVE
SAVE
Page 24
Page 24 LAARS Heating Systems
• Standby units are used for backup or extreme load conditions only. A Standby Stage can never be a Lead Stage
• 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 unit
from starting if the other units can eventually meet the load, or if the load decreases.
• When setting Standby Time, remember that it will be added to the Reaction Time for the first stage on the first Standby unit.
The following stages start time will rely on Pre-Purge and Reaction Time.
LAST STAGE HOLD
Adjustable 0ºF/0ºC - 30ºF/17ºC Default: 5ºF/3ºC
Button: MENU/<System Settings>/<Stage Settings>/Last Stage Hold in PID Logic only
• The Last Stage Hold prevents short cycling of the Lead Stage during low load conditions
LAST STAGE HOLD
0
F
[ ]
BACK
SAVE
where the system might have a load that is significantly less than the output of one stage.
When the S8 brings on the Lead Stage, the Set Point is quickly exceeded, and the Lead Stage is turned off.
• To prolong the run time during this type of condition, use the Last Stage Hold setting.
• In heating, the S8 will allow the system temperature to exceed the Set Point by the number of degrees selected, before the
Lead Stage is turned off. In cooling, the the S8 will allow the system temperature to rise above 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 fire,
until the Set Point reaches 170°F then turn off.
THROTTLE RANGE
Adjustable 2ºF/1ºC - 20ºF/11ºC Default: 2ºF/1ºC
Button: MENU/<System Settings>/<Stage Settings>/Throttle in OSS Logic only
• The Throttling Range sets a temperature band around the Set Point that controls when
-- THROTTLE RANGE --
2
F
[ ]
SAVE
BACK
stages will be turned on or off.
• For example, in the Oversize (OSS) heating mode, no stages will be activated until the temperature falls one full Throttling Range
below the Set Point. A second stage will be activated when the temperature falls to two full Throttling Ranges below the Set
Point, and so on, with one extra stage being turned on for every throttling below the Set Point the System temperature reaches.
• Stages will be turned off as the temperature rises toward the Set Point with one full throttling range as a differential.
• The last stage to be turned off will be allowed to exceed the Set Point by a full throttling range before it is turned off. This helps
to prevent the last stage from short cycling when the load is low or when the stage is oversized.
Throttling Example in Heating Mode
Set Point = 180°F Throttling = 5°F 4 Boiler Stages, A, B, C, and D
Falling Temperature Rising Temperature
Temperature Calculation Stage Turned On Stages On Stage Turned Off Stages On
185°F
180°F 180 - (0)THR None None None A
175°F 180 - (1)THR A A B A
171 to 174°F --- --- A --- A,B
170°F 180 - (2)THR B A,B C A,B
166 to 169°F --- --- A,B --- A,B,C
165°F 180 - (3)THR C A,B,C D A,B,C
161 to 165°F --- --- A,B,C None A,B,C,D
160°F 180 - (4)THR D A,B,C,D None A,B,C,D
180 + (1)THR
None None A None
LEAD SETTINGS
Button: MENU/<System Settings>/<Stage Settings>/<Lead Settings>
The lead menu is to help in setting the Lead unit and type of rotation approperiate for the
system.
-- LEAD SETTINGS - Lead Boiler AB
Rotate Mode Time
BACK
SELECT
Page 25
LAARS Sequencing Controls S8 & S8EXT
LEAD BOILER
Depending on the number of stages Default: The first set of stages
Button: MENU/<System Settings>/<Stage Settings>/<Lead Setting>/Rotate Mode
• The Lead Unit’s lowest stage will always be the first stage brought on when there is a
call for output. As more output is needed, additional Stages are added.
• The Lead Unit is always shown on the main display in brackets.
• In a 2-Stage system (see Boiler Type in the Startup section), the display will show the
two Lead Unit stages bracketed <AB>. In a 3-Stage system, the display will show the
three Lead Unit stages bracketed <ABC>, and so on.
• If Pump or Valve is selected as the Boiler Output in the Startup menu, the Valve or Pump
letter will be skipped from the number of stages. See example to the right. The missing
stage C and F represent the Unit Valve or Pump.
• The Lead Unit can be rotated based on the Rotation Mode selected. (See next setting)
Page 25
No Pump or Valve stages
-- LEAD BOILER --
BACK
with Pump or Valve stages
-- LEAD BOILER - AB
DE
BACK
SELECT
SELECT
ROTATE MODE
Adjustable Time (1 hr to 999 hrs), Manual, FOFO Default: Time (24Hours)
Button: MENU/<System Settings>/<Stage Settings>/<Lead Setting>/Rotate Mode
• The Lead Unit is the first unit brought on when output is required.
• The Lead Unit can be rotated automatically, manually or based on First-On/First-Off
(FOFO). The automatic rotation is recommended for most applications.
• The current Lead Unit is shown in brackets on the main display.
• Only units which are set to Auto Mode can be Lead. Therefore, not all the units may be
available when manually selecting a new Lead Unit.
• If Time is selected, a second screen will allow the adjustment of the Auto Rotate Period
If 24 Hours (default setting) was selected, the first rotation will take effect after 12 hours
if the Time was not set. However, if the Time was set, the rotation will always take
place at 2:00AM. The following rotations will take place every 24 hours thereafter.
• If First-On/First-Off (FOFO) is selected, the concept will follow this example; If A is the
Lead, the starting sequence will be A, B, then C. When the de-energizing of the stages
starts it will turn off A, B, Then C. Then stage D will be the new lead for the next load.
SETBACK SCHEDULE
Button: MENU/<System Settings>/<Stage Settings>/<Setback Schedule>
This menu provide the Day/Night Schedule as well as the Setback and Boost settings.
SETBACK
Adjustable 0°F/0°C to 80°F/44°C Default: 0°F/0°C
Button: MENU/<System Settings>/<Setback Schedule>/Setback in Day/Night Schedule
Button: MENU/<System Settings>/Setback in External Signal
• The Setback feature can be used to provide the S8 with a lower temperature Set Point in
Heating or a higher Set Point in Cooling when less load is required.
• For example, if in heating the calculated temperature is 180°F and the Setback is 20°F, then when in Setback, the S8 will hold a
Set Point of 160°F. The new Set Point will appear on the main display indicating this condition "Setback to 160
• A typical use for Setback is to provide less system temperature in heating to a building during the night or on the weekends
when building is not occupied, but heat is still required.
• After selecting a value in Setback, you'll be directed to the Boost menu.
-- LEAD ROTATION - Time
Manual
FOFO
SELECT
BACK
AUTO ROTATE PERIOD
24hrs
[ ]
BACK
SETBACK SCHEDULE
Setback 0
Present Time **:**
Day Schdule 7:00Am
Night Schdul 7:00Pm
BACK
------ SETBACK ------ 0
[ ]
BACK
If Time Rotation is selected
SAVE
SELECT
F
SAVE
F".
F
BOOST
Adjustable 0°F/0°C to 80°F/44°C Default: 0°F/0°C
Button: MENU/<System Settings>/Setback/Boost
• This features allows a building to either warm up or cool down quickly after a Setback
period to bring the building to the desired temperature faster.
• The Boost temperature will be the number of degrees to be added in Heating or subtracted in Cooling from the Calculated
Target Temperature.
• Using the previous example, if the Target was 180°F and the Setback was 20°F and the Boost was 10°F for 30 minutes, after the
setback period, the Boost will change the target to 190°F for a period of 30 minutes. The new Set Point will appear on the main
display indicating this condition "Boost to 190
F".
-------- BOOST -------- 0
[ ]
BACK
F
SAVE
Page 26
Page 26 LAARS Heating Systems
BOOST PERIOD
Adjustable 0 to 120 minutes Default: 30 minutes
Button: MENU/<System Settings>/Setback/Boost/Boost Period
• This will determine the amount of Boost the system will receive.
• If External Signal was selected as the Setback Mode, the Boost will start when the
switch from Setback to normal operation takes place and will continue for the full Boost Period. An example would be if
the Boost Period was set to 30 minutes and the shorting of the Setback terminals has ended at 7:00Am, the Boost will start at
7:00Am and will terminate at 7:30Am where the control will resume normal operation.
• If Day/Night Schedule was seleceted as the Setback Mode, the Boost will start a full Boost Period prior to the switch from
Night Setback to Day normal operation. If the Day was set to start at 7:00Am, the Boost Period was set to 30 minutes, the
Boost will start at 6:30Am and terminate at 7:00Am.
Avoiding Conflicting Boiler Limits
• The temperature limits set on the boilers MUST be set considerably higher than the S8’s
Set Point for the reasons detailed below.
• The S8 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
read by the S8 sensor, the Last Stage Hold setting must be accounted for. The boiler limit must be set above the Set Point PLUS
the Last Stage Hold PLUS the normal drop experienced in the piping.
• Using the previous example of a 10°F Last Stage Hold with a 160°F Set Point, the boilers’ limits must be set enough over 170°F
to prevent the boilers’ internal limits being reached. In this situation, the boiler high limit should be set at approximately 180°F
to prevent the difference in boiler temperature vs. header temperature causing erratic operation.
------ BOOST PERIOD-- 30min
[ ]
SAVE
BACK
WARNING
The temperature limits set
on the boilers must be higher
than the S8 Set Point. Read
the section at left for details
that will prevent erratic system
operation.
DAY/NIGHT SCHEDULES
Button: MENU/<System Settings>/<Setback Schedule>/Day Schedules
• The S8 has two levels of heat or cool. The Day level is used when a building is
occupied and people are active.
• The Night (Setback) level is used when a building is not occupied, or when people are
sleeping. This setting reduces the calculated temperature in Heating and increase it in
Cooling by the Setback setting. In Heating, if the Day calculated water temperature was
150˚F and the Setback was 20˚F, the Night Schedule will run at (150˚F - 20˚F) = 130˚F.
• If the Boost feature is being used, it uses the Day Schedule as a Boost ending point. That is, if the Day Schedule is set to start
at 6:00AM,the Boost was set to 10ºF, and the Boost Period was 30 minutes, the Boost will start at 5:30AM. The S8 will then
raise the calculated water temperature by the Boost amount. Using the previous example, at 5:30AM the S8 will raise the
calculated water to 160˚F (150˚F + 10˚F) until 6:00AM.
SET PRESENT TIME
Button: MENU/<System Settings>/<Setback Schedule>/Present Time
Button: MENU/<Maintenance>/Present Time
• The Time is used for Day/Night Schedule and History graph.
• Adjust the time by selecting Time from the menu and then scrolling through the hours
followed by the minutes. If hours are to be set to PM, scroll through the AM hours to
reach the PM hours.
-- DAY SCHEDULE ----
07:**Am
BACK
-- NIGHT SCHEDULE --
10:**Pm
BACK
- SET PRESENT TIME
**:**
BACK
SAVE
SAVE
SAVE
CAUTION
Remember that the battery is the backup for the Time. If no power is supplied to the S8 and there
was no battery or battery had no power, time values will be lost and will need to be reset.
Page 27
LAARS Sequencing Controls S8 & S8EXT
Page 27
DHW SETTINGS
Button: MENU/<System Settings>/<DHW Settings>
• A DHW call can be initiated by shorting the DHW input terminals, 33 and 34. In
addition, using a Laars temperature sensor on the same terminals instead of a dry contact
input will add the DHW Set Point and Differential control capability.
• In addition to raising the Target to either 200ºF or the Maximum Target on a DHW call,
which ever is lower, the S8 provides three levels of DHW pump operation. The
first is when Primary/Secondary is selected as the DHW Piping from the Startup Menu. This option will provide no DHW
Priority. Furthermore, if there was a DHW call during the Summer or when the outdoor temperature is above the Outdoor
Cutoff, both the DHW Pump and the System relays will energize. Upon the termination of the DHW call, the DHW Pump relay
will de-energize leaving the System relay energized for the Run-On delay.
• The other two DHW options are available when Parallel is selected as the DHW Piping from the Startup Menu. These two
options will not allow the System relay to energize in the Summer or when the outdoor temperature is above the Outdoor Cutoff
on a DHW call.
• In Winter, if the DHW Priority Timer was set to NO, a DHW call will keep the System relay energized in addition to energizing
the DHW Pump relay. Upon termination of the DHW call, the DHW Pump relay will de-energize leaving the System relay on.
• In Winter, if the DHW Priority Timer was set to a value other than NO, a DHW call will de-energize the System relay and
energize the DHW Pump relay. This will remain for the period of the DHW Priority Timer setting or until the DHW call
terminates, whichever is sooner. If the DHW call was still active after the DHW Priority Timer elapses, the System relay will
energize for the remaining of the DHW call period.
-- DHW SETTINGS -- DHW Temp. 120
DHW Prior Tmr 60min
DHW Set Point 120
DHW Diff. 5
BACK
SELECT
F
F
F
DHW PRIORITY TIMER (AVAILABLE WITH PARALLEL DHW PIPING)
Adjustable NO, 1 to 120 minutes Default: NO
Button: MENU/<System Settings>/<DHW Settings>/DHW Prior. Timer in Parallel
• The DHW Priority Timer provides the user with the capability of selecting the
DHW Priority period. If NO was selected, both DHW Pump and System relay will
be energized on a DHW call whenever the control is set to Winter and the Outdoor
temperature is below or at the Outdoor Cutoff.
• In Summer, a DHW call will energize only the DHW Pump relay leaving the System relay de-energized.
• If the DHW Priority Timer was set to a value other than NO, a DHW call in the Winter when the Outdoor temperature is below
the Outdoor Cutoff will cause the System relay to de-energize and the DHW Pump relay to energize for the period of the DHW
Priority Timer or until the DHW call expertise, whichever happens sooner. If the DHW call did not expire within the Priority
period, then the System relay will energize.
• If there was a DHW call during Summer or when the Outdoor temperature is above the Outdoor Cutoff, only the DHW Pump
relay will energize.
DHW PRIORITY TIMER
2min
[ ]
BACK SAVE
DHW SET POINT (REQUIRES AN OPTIONAL DHW TEMPERATURE SENSOR)
Adjustable 100°F/38°C to 200°F/93°C Default: 160°F/71°C
Button: MENU/<System Settings>/<DHW Settings>/DHW Set Point
• This is the desired DHW temperature setting at which the DHW Pump relay will deenergize when reached.
• The S8 can accept a DHW call in two ways. An aquastat can provide a dry contact
closure to terminals 33 and 34 is the first option.
• The second option will be connecting a Laars temperature sensor (CA002400 or equivalent) for immersion in a 3/8ID well
(CA002500 or equivalent) will offer the capability of adjusting the DHW Set Point and Differential through he S8 easy to
follow menu. In addition to being able to view and log DHW temperature history.
DHW DIFFERENTIAL
Adjustable 5°F/3°C to 80°F/44°C Default: 10°F/6°C
Button: MENU/<System Settings>/<DHW Settings>/DHW Diff.
• This represents the number of degrees the DHW temperature can drop from the DHW
Set Point before a DHW call can be recognized and the DHW Pump relay energized.
• Larger Differential will result in larger fluctuation in DHW temperature. However,
small Differential will have a tighter control over the DHW temperature but might result
in boilers coming on frequently for short periods to satisfy the DHW Set Point and
Differential settings.
-- DHW SET POINT - 160
[ ]
BACK
DHW DIFFERENTIAL
10
[ ]
BACK
F
SAVE
F
SAVE
Page 28
Page 28 LAARS Heating Systems
PUMP, VALVE, AND COMBUSTION AIR DAMPER OPERATION
• The S8 controls multiple relays each controlling different types of equipment. In addition to the control of the boilers or
cooling units, it can control, the primary system pump, unit pumps or valves, a DHW pump, and a combustion air damper. The
operation of those relays depends on the Startup and System Settings.
RUN-ON
Adjustable 0 to 60 minutes Default: 2 minutes
Button: MENU/<System Settings>/Run-On
• The Run-On applies to all pumps, valves and dampers. It is the additional time a pump,
valve or a combustion air damper will run after the output unit relays has de-energized.
For pumps and valves it is used to dissipate the excess energy from the heating or
cooling system into the building. For a combustion air damper, it brings in enough fresh air for the next boiler fire up.
• The Run-On time should be set based on the size and type of the equipment. A boiler with low water content and high
horsepower will need a longer Run-On than a boiler with the same horsepower but has more water content.
------- RUN-ON ------ 2min
[ ]
BACK
SAVE
PUMP EXERCISE
Adjustable Off, On Default: Off
Button: MENU/<System Settings>/Pump Exercise
• The S8 provides an option to exercise pumps for 10 seconds when not used for seven
days. This option reduces pumps' impellers locking during the off-season period.
MAINTENANCE
Button: MENU/<Maintenance>
The Maintenance menu gives access to sensor and outputs trimming. In addition, you'll have
access to view the Startup configuration settings as well as sensor histories
CAUTION
To be able to change the S8 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 padlock.
SYSTEM & OUTDOOR SENSOR TRIM
Adjustable -20°F/-11°C to +20°F/+11°C Default: 0°F
Button: MENU/<Maintenance>/System Trim
Button: MENU/<Maintenance>/Outdoor Trim
Button: MENU/<Maintenance>/Return Trim
Button: MENU/<Maintenance>/DHW Trim
• The Laars thermistor type sensors are very accurate, and normally require no calibration.
However, sometimes it may be desirable to make small adjustments to the displayed
value.
• Do not use the Trim setting to make the Outdoor temperature sensor match the reported
on the radio or TV. Outdoor temperature can vary widely over a broadcast range.
--- PUMP EXERCISE - Off
On
BACK
---- MAINTENANCE --- Unit F
Present Time 12:30P
<Sensor Trim>
<Histories>
<Configuration>
BACK
--- SENSOR TRIM --- System Trim +0 F
Outdoor Trim +0
Return Trim +0
DHW Trim +0
BACK
SAVE
SELECT
SELECT
F
F
F
HISTORY
Button: MENU/<Histories>
The S8 provides users with a graphical history of the System, Outdoor, DHW, and Return
temperatures for the previous 24 hours. The temperatures are sampled every 12 minutes. That
is, readings of temperatures are recorded and stored every 12 minutes for the last 24 hours.
Sys=120 F 10:00AM
BACK NEXT
Page 29
LAARS Sequencing Controls S8 & S8EXT
Sys=
155
F OD=
58
F
DHW all (200 F)
<AB > DE GH JK
HI HI LO ----
BOILER MENU
Outdoor Temp
System Temp
Message Display Line
Units and their
Status
Button functions
Button
• To view the values of specific time period, use the two middle buttons to scroll to that time and read the upper left temperature.
• The first screen will be the System Temperature History. By clicking on the Next button, you'll be able to view the Outdoor
Temperature History, then, the Return History followed by the DHW History.
Page 29
CONFIGURATION
Button: MENU/<Maintenance>/<Configuration>
• This menu option provides a consolidated view of the Startup settings.
• Additional settings will be available by selecting the NEXT option.
DISPLAY
The S8 display layout provides a variety of information that gives an immediate picture of
the operation status. The display shows four heating or cooling units at a time. The two
middle buttons scrolls the screen to view additional boilers. Moreover, all the information is
brightly displayed. It can be viewed in brightly or dimly lit rooms.
• The buttons' functionality changes based on the screen and menu level. The buttons'
functionality is displayed on a dark background on the screen bottom line.
• Horizontal arrows are to scroll through the available stages.
• Vertical arrows are to scroll through the menu functions
when in menus or to change values of settings when in its
specific screen.
S8 V1.00
Outdoor reset
Heating-BreakOnRise
Day/Night Schedule
DHW Parallel
BACK
8 X On/Off
PID,Fault Stgs Off
BACK
NEXT
NEXT
DISPLAY OUTPUT STATUS
The S8 unit sequencing status gives immediate access to each unit status. The following list show all possible boiler status:
• <AB> Two-Stage unit and Unit AB is the Lead in sequencing. (Brackets indicate Lead Stage).
• --- Unit is de-energized. The unit Mode is set to Auto.
• STB Unit is set to be a Standby Unit.
• HI Unit highest stage is active. The unit Mode is set to either Auto or Standby.
• MED Unit Middle stage is active. Available in Three-stage units only. The unit Mode is set to either Auto or Standby.
• MHI Unit Middle High stage is active. Available in Four-stage units only. The unit Mode is set to either Auto or Standby.
• MLO Unit Middle Low stage is active. Available in Four-stage units only The unit Mode is set to either Auto or Standby.
• LO Unit Lowest stage is active. The unit Mode is set to either Auto or Standby.
• ON All Unit Stages are set to ON.
• OFF All Unit Stages are set to OFF or unit does not exist.
• C/E Unit on Extension panel is not communicating back to the S8..
Unit Pumps are being controlled by the S8.
•
Unit Valves are being controlled by the S8.
•
DISPLAY MESSAGES
The S8 normal display layout reserved the second line for message indications. The following is a list of the most common Message
Display Line information:
• Summer The control is set to Summer. No heat is active.
• Winter The control is set to Winter. No cooling is active.
• Outdoor Cutoff The Outdoor temperature is above the Outdoor Cutoff in heating or below it in cooling.
• Shutdown Active The Shutdown Terminals are Shorted. No heating or cooling units will be active.
• Shutdown by EMS The EMS is below 2mA or above 22mA
• DHW Call (171˚F) There is a DHW (Domestic Hot Water) call. The S8 will Raise system Set Point to the indicated
temperature. DHW increases calculated temperature to 200˚F or Max Water Temperature, whichever
is lower.
Page 30
Page 30 LAARS Heating Systems
and XSIG Interface using RS485
S8
SYSTEM
DHW PUMP
SENSORS MUST BE GOLD SERIES
SYS=144F OD=35F
<AB > DE GH JK
HI LO -- OFF
STAGE MENU
SYSTEM
PROGRAM RUN
DO NOT APPLY ANY VOLTAGE TO INPUT TERMINALS
COMB. AIR
C US
CAUTION:
Risk of Electric Shock.
Use Copper Conductors Only.
I
J
K
Q
R
S
S8
SEQUENCING CONTROL
• Holding Return at 110˚F The Return sensor is reading less than the Minimum Return. S8 is trying to raise return to 110˚F.
• Holding Until 150˚F The Lead boiler is in Last Stage Hold. This example shows that the lead stage will turn off when
system temperature reaches 150˚F.
• Waiting for Comb. Prove The System or Combustion Air Damper relay is ON and the prove terminals are open before the lead
boiler relay can energize.
• SYS Prove Failure After boilers have run for a while, Prove signal was opened. The boiler relays will de-energize.
However, the System relay will remain energized.
STAGE SETTINGS
Button: BOILER/
• In most installations, all active unit adjustments are the same, but each can be configured
differently if desired.
• When the BOILER or C.UNIT button is depressed, the Unit A Settings menu will be
shown.
• Make all the appropriate settings for Unit A (See below).
• Then select the Next Stage option from the menu to bring up the Boiler B Settings menu
and make all the settings. Continue until all boilers have been set.
• If a S8EXT is connected to the S8, scrolling through stages using the Next and Prev
Stage menu options will scroll through the S8EXT stages as well.
----- BOILER AB ---- Mode Auto
Runtime 58Hrs
<Prev Boiler>
<Next Boiler>
BACK
SAVE
CAUTION
To be able to change the S8 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 padlock.
MODE
Auto, Standby, Off, On Default: Auto
Button: BOILER/Mode
• The S8 only controls any unit set to Auto or (after a delay) those set to Standby. None of
the other settings is recommended for output units connected to active units.
• Any output without an active unit connected must be set to Off.
• The following list describes the MODE options:
Auto - The S8 will control the unit’s operation to maintain the desired Set Point. Only units set to Auto can be Lead.
-- BOILER AB MODE Auto
Standby
Off
On
BACK
SAVE
Standby Standby units can only be activated when all units in Auto have been at HI for an adjustable Standby delay period.
Off Any output unit A through D not connected to a physical unit should be set to Off. The Off Mode can also be used to
On The On Mode should only be used when testing a unit. The On Mode overrides the PROVE input. Once set to On the unit
RUNTIME
Clear
Button: BOILER/RunTime
• The RunTime provides an accumulative hourly run for the selected unit.
• The RunTime for a specific unit can be reset to zero by pressing the middle two buttons.
Standby is generally used when you want a specific unit to be available in extreme load conditions. Note that a Standby
unit Cannot be a Lead unit. Standby Time is only available in PID mode.
disable units that are being serviced. The number of units and their stages are selected in the Startup menu.
will immediately start all of its stages.
BOILER AB RUNTIME
58hrs
BACK
CLEAR
OK
Page 31
LAARS Sequencing Controls S8 & S8EXT
TROUBLESHOOTING
Page 31
TEMPERATURE INPUTS
Display shows Sensor OPEN
Check the sensor is connected and the wires are continuous to the S8. Finally follow the
procedure for Incorrect Temperature Display.
Display shows Sensor SHORT
The S8 sees a short across the input terminals. Remove the wires from the sensor terminals.
The display should change to read OPEN. If it doesn’t, the S8 may be damaged.
Display shows an Incorrect Temperature Display
Remove the wires from sensor terminals. The display should change to read OPEN. If it
doesn’t, the S8 may be damaged. Take an ohm reading across the detached sensor wires. The
ohm reading should correspond to the side chart. If it doesn’t, the sensor may be damaged.
Return Sensor does not Display Temperature
Check the sensor is connected and the wires are continuous to the S8. Finally follow the
procedure for Incorrect temperature display.
CONTROL OPERATION
Too Much Heat
Check if the control has any of the following:
• Domestic Hot Water call - The S8 will raise the temperature of the system to either 200˚F or
Maximum Target on a DHW call.
• Reset Ratio and Offset - If excessive heat occurs only in certain weather conditions, adjust
the Reset Ratio and Offset (See Understanding Operating Concept). If excessive heat occurs
year round, reduce the Offset.
• Unit Mode Settings - The S8 will only sequence boilers their mode is set to Auto or Standby.
Check to see if any boiler stage is set to On.
• Control Settings - The Last Stage Hold will allow only the Lead boiler to stay on for an
additional number of degrees. If the setting is too high, and only the Lead boiler is on, the
system can over heat. Reduce the Last Stage Hold setting.
Too Little Heat
Check if the control has any of the following:
• Reset Ratio and Offset - If reduced heat occurs only in certain weather conditions, adjust the
Reset Ratio and Offset (See Understanding Operating Concept). If reduced heat occurs year
round, increase the Offset.
• Setback and Day/Night Schedule - If reduced heat occurs only during specific hours, check
the Day/Night Schedule and the Setback, Boost, and Boost Period values. Either reduce the
Setback or Boost settings or change the Day and Night Schedules.
• Boiler Mode Settings - The S8 will only modulate boilers their mode is set to Auto or
Standby. Check if any boiler stage is set to Off or Standby.
Temperature Sensor Chart
TEMPERATURE
(in Degrees °F)
-30 117720
-20 82823
-10 59076
0 42683
10 31215
20 23089
25 19939
30 17264
35 14985
40 13040
45 11374
50 9944
55 8714
60 7653
70 5941
80 4649
90 3667
100 2914
110
120 1879
130 1524
140 1243
150 1021
160 842
170 699
180 583
190 489
200 412
210 349
220 297
230 253
240 217
250 187
Value
(in Ohms)
2332
Units are Short-Cycling
• Minimum Runtime - Increase the Minimum Runtime only if all units tend to short-cycle.
• Last Stage Hold - Increase the Last Stage Hold only if the lead unit tends to short-cycle.
System is Overshooting or Undershooting
• Reaction Time and Minimum Runtime - If the system is overshooting or undershooting, adjust Minimum Runtime or the
Reaction Time. That depends on if the stages are brought on fast and were not allowed to turn off until the Minimum Runtime
elapsed. Or, the stages were brought on slowly, however, were allowed to turn off quickly.
• PID vs OSS - If the application the system is used on requires fast response that the normal PID mode cannot provide, try using
the OSS mode and adjust its parameters according to the system requirements.
Page 32
Page 32 LAARS Heating Systems
Outdoor
Sensor
System
Sensor
120VAC
Boiler 1
Boiler 2
Boiler 3
Boiler 4
Building Heating Loop
SQ-Elite
SYSTEM
DHW PUMP
INPUT RATINGS:
115VAC 60Hz, 12VA MAX
Use Copper Conductors Only.
CAUTION:
Risk of Electric Shock.
PWR
L N
1 2
SENSORS MUST BE GOLD SERIES
SYSTEM
3
DHW
PUMP
5
Stage A7Stage B9Stage C
11
13
Stage E15Stage F
17
Stage D
6 8 10 12 14
16 18
RS485
SYS=144F OD=35F
<AB
> DE GH JK
HI LO -- OFF
4
Stage G19Stage H
21
OUTDOOR
TEMP
27 29
31
DHW
33
SHUTDOWN
/SETBACK
35
RETURN
TEMP
20 22 28 30 32 34 36
STAGE MENU
Stage E
Stage F
Stage G
Stage H
Stage A
Stage B
Stage C
Stage D
25
26
PRESS
+ -
37
38
PROVE
SYSTEM
TEMP
PROGRAM RUN
23 24
COMB.
AIR
DO NOT APPLY ANY VOLTAGE TO INPUT TERMINALS
COMB. AIR
ENCLOSED
ENERGY
MANAGEMENT
EQUIPMENT
LISTED
99RA
C US
System
Pump
S8
SEQUENCING CONTROL
MULTIPLE BOILERS WITH PUMPS
PIPING DIAGRAM
System:
The S8 sequencing 4 single-stage boilers and their boiler pumps. The boilers are piped in Reverse Return on the primary
loop. The System output is controlling the System Pump.
Laars Heating Systems is aware that each installation is unique. Thus, Laars Heating Systems is not responsible for any
installation related to any electrical or plumbing diagram generated by Laars Heating Systems. The provided illustrations
are to demonstrate Laars Heating Systems’s control operating concept only.
Page 33
LAARS Sequencing Controls S8 & S8EXT
Sensor Shiled
System Sensor
Shutdown
Dry Contact
Unit1
Unit1
Pump
System
Pump
SYSTEM
DHW PUMP
INPUT RATINGS:
115VAC 60Hz, 12VA MAX
Use Copper Conductors Only.
CAUTION:
Risk of Electric Shock.
PWR
L N
1 2
SENSORS MUST BE GOLD SERIES
SYSTEM
3
DHW
PUMP
5
Stage A7Stage B9Stage C
11 13
Stage E15Stage F
17
Stage D
6 8 10 12 14
16 18
RS485
SYS=144F OD=35F
<AB
> DE GH JK
HI LO -- OFF
4
Stage G19Stage H
21
OUTDOOR
TEMP
27 29 31
DHW
33
SHUTDOWN
/SETBACK
35
RETURN
TEMP
20 22 28 30 32 34 36
STAGE MENU
Stage E
Stage F
Stage G
Stage H
Stage A
Stage B
Stage C
Stage D
25 26
PRESS
+ -
37 38
PROVE
SYSTEM
TEMP
PROGRAM RUN
23 24
COMB.
AIR
DO NOT APPLY ANY VOLTAGE TO INPUT TERMINALS
COMB. AIR
ENCLOSED
ENERGY
MANAGEMENT
EQUIPMENT
LISTED
99RA
C US
Unit2
Unit2
Pump
Sensor Shiled
Outdoor Sensor
Unit3
Unit3
Pump
Unit4
Unit4
Pump
L
N
Prove
Dry Contact
S8
SEQUENCING CONTROL
MULTIPLE BOILERS
WIRING DIAGRAM
Page 33
Page 34
Page 34 LAARS Heating Systems
SPECIFICATIONS:
Voltage Input: . . . . . . . . . 120 VAC 60 Hz
Power Consumption: . . . . . . . 12 VA Max
Operating Temperature: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20°F/-7°C to 120°F/49°C
Operating Humidity: . . . . . . . 20% to 80%
Dimensions: . . . . . . . . . 11"W x 9" H x 3 ¾
Weight: . . . . . . . . . . . . . . . 2.5 pounds
S8 Specifications:
Lead Stage Rotation: . . . . . . . . . . . . . . . . . . . . . . . Time ( 1 to 999 Hours (41 days)), Manual, First-On/First-Off
S8 Outputs and LEDs: . . . . . . . . . . . . . . . . 11 N.O. S.P.S.T (8 Stages, 1 System, 1 DHW Pump, 1 Combustion Air)
S8 Inputs: . . . . . . . . . . . . . . . . . . 1 Sys(Temp), 1 Outdoor, Return Temp, DHW Temp, Ext Setback/Shutdown, Prove
Stage Modes: . . . . . . Auto, Standby, Off, On
Standby Time (PID only): . 1 to 60 minutes
Output Relay Ratings: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Amp inductive at 120 VAC 60 Hz
Add-On S8EXT Panels: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . up two S8EXT Panels using RS485
Temperature Display: Fahrenheit or Celsius.
Display: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Graphical Alphanumeric (7 rows x 21 char. each)
Temperature Sensor Ranges: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -35°F/-37°C to 250°F/121°C
Outdoor Cutoff Range: . . . . . . . . . . . . . . . . . . . . . . . . . . . 20°F/-7°C to 100°F/38°C, ON and OFF
Set Point: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -10°F/-23°C to 230°F/110°C
External Set Point: . . . . . . . . . . . . . . . . . . . . -10°F/-23°C to 240°F/116°C using XSIG Interface (optional)
Reset Ratio Range (Outdoor Reset Only): . . . . . . (8:1) to (1:4) (Outdoor : System Water), and Custom Reset Ratio
Offset Adjustment (Outdoor Reset Only): . . . . . . . . . . . . . . . . . . . . . . . . -40°F/-22°C to plus 40°F/22°C
Minimum Target (Outdoor Reset Only): . . . . . . . . . . . . . . . . . . . . . . . . 70°F/21°C to 170°F/77°C
Maximum Target (Outdoor Reset Only): . . . . . . . . . . . . . . . . . . . . . . . 90°F/32°C to 240°F/116°C
Reaction Time (PID only): . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 to 10 minutes
Minimum Run-Time (PID only): . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 to 60 minutes
Purge Delay (PID only): . 0.0 to 10.0 minutes
Last Stage Hold (PID only): . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0°F/0°C to 30°F/17°C
Throttle Range (OSS only): . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2°F/1°C to 20°F/11°C
Domestic Hot Water Priority Options: . . . . . . Parallel Piping with Priority or without Priority and Primary Secondary
Pump Run-On: . . . . . . . . . 0 to 60 minutes
Pump Exercise: . . . . . . . . . . . Yes or No
Schedules: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Day and 1 Night (Setback) settings per day
Night Setback: . . . . . 0°F/0°C to 80°F/44°C
Power Backup: . . . . . . . .Lithium coin battery, 100 days minimum 5 year replacement (Maintains Clock in power outages).
External Inputs: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Shutdown Input, and Prove Input. (Dry Contacts Only)
Season: . . . . . . . . . . . Winter and Summer.
S8EXT Specifications:
Extension Numbering: . Toggle Switch A or B
LED: . . . 1 Power (Dual Color Green (A)/Red (B)), 1 Communication, 8 Stage Output relays (Dual Color Green (A)/Red (B))
Stage Outputs: . . . . . . . . . 8 N.O. S.P.S.T.
Output Relay Ratings: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Amp inductive at 120 VAC 60 Hz
Connection to S8 and another S8EXT: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Two RS485
Page 35
LAARS Sequencing Controls S8 & S8EXT
Page 35
Page 36
LAARS Heating Systems
800.900.9276 • Fax 800.559.1583 (Customer Service, Service Advisors)
20 Industrial Way, Rochester, NH 03867 • 603.335.6300 • Fax 603.335.3355
1869 Sismet Road, Mississauga, Ontario, Canada L4W 1W8 • 905.238.0100 • Fax 905.366.0130
www.Laars.com Litho in U.S.A. © Laars Heating Systems 0806 Document 4213
HTC#059065-00 Rev.A
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