LAARS M4-LHS - Installation Manual User Manual
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M4-LHS installation and Operation Manual
Too Little Heat
• Reset Ratio and Offset - If reduced heat occurs only in certain weather conditions, adjust the
Reset Ratio and Offset (See "Outdoor Reset Concept" on page 5). 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 values. Then, reduce the Setback setting. See "Setback" on
• Boiler Mode Settings - The M4-LHS will only control boilers their mode is set to Auto or
Standby. Check if any boiler stage is set to Manual, Off, or Standby. See "Mode" on page 39.
Boilers are Short-Cycling
• Lag Delay - Increase the Lag Delay only if modulating boilers tend to short-cycle.
• Minimum Runtime - Increase the Minimum Runtime only if staging boilers tend to short-cycle.
• Last Stage Hold - Increase the Last Stage Hold only if the lead boiler tends to short-cycle.
System is Overshooting or undershooting
Modulating Boilers
• Gain - If when using modulating boilers the system is overshooting reduce the Gain. See "Gain"
• Gain - If when using modulating boilers the system is undershooting increase the Gain.
Staging Boilers
• Reaction Time - If when using staging boilers the system is overshooting increase the Reaction
Time. As the stages will be turning on faster than they are affecting the system. If the system
was undershooting for long periods, reduce the Reaction Time. See "Reaction Time" on page 34.
• Minimum Runtime - If when using staging boilers the system is overshooting reduce the
Minimum Run Time. If the system was undershooting, increase the reaction time as it is turning
off stages quicker than needed. See "Minimum Runtime" on page 34.