LAARS M4-LHS - Installation Manual - Manual (Page 4)

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M4-LHS installation and Operation Manual
MODuLaTiNg LOgiC OVErViEW
The Modulation PID logic is capable of controlling multiple modulating current or voltage boilers. When heat is required, the control
PID activates the lead boiler and starts its purge. See "Purge Delay" on page 31. This is followed by the initiation of its modulation at
the Ignition %. See "Ignition %" on page 40. When additional heat is needed, the control starts to increase the lead boiler modulation
until the Modulation Start % has been reached. See "Modulation Start %" on page 40. Any additional heat requirement starts the lag
boiler purge. While the lag boiler is in purge, the lead boiler resumes its modulation until it reaches full fire (100% modulation).
Additional heat requirements triggers the control to increase the lag boiler modulation.
When the M4-LHS PID requires reduced output, it will reduce the modulation of the lag boiler until it reaches its Ignition %. That
shall be followed by the reduction of modulation of the lead boiler until it reaches 40% percent of the Modulation Start %. This shall
trigger the control to turn off the lag boiler. The control will keep reducing the lead boiler modulation until it reaches its Ignition %.
If the Last Stage Hold was activated, the control will hold the lead boiler at the Ignition % until the System Temperature exceeds the
Target Set Point by the Last Stage hold setting. See "Last Stage Hold" on page 32.
For Modulating boilers, See "Boiler Type" on page 19. Also, See "HYBRID Modulating Boiler Settings" on page 22.