Boiler minimum return – LAARS S8Ext - Installation Manual User Manual
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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/
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
---- MIN TARGET ----
120 F
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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/
in Outdoor Reset only
• This is the highest temperature heating water the S8 will circulate through the heating
system.
---- MAX TARGET ----
240 F
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• 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)..
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.
---- MIN RETURN ----
120 F
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• 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 F" in the Display Message Line to
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.
---- RETURN LAG ----
2min
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