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Domestic Hot Water Operation
The control is compatible with boilers with include a domestic hot
water tankless coil . When the aquastat on the DHW tankless
calls for heat, the control fires boiler 1 . Boiler 2 is not operated
for DHW calls . When a programmable schedule is used, the
DHW Unoccupied setting selects whether to respond to DHW
calls for heat .
Combustion Air Damper Operation
Combustion Air Damper
The combustion air damper relay closes when a heating
cycle is started or a DHW call is received and the control has
determined that one or more boilers need to be turned on .
Combustion Air Delay
The control waits until the combustion air damper delay
elapses before staging on any boilers .
Boiler Operation
Boiler Available
Select the boiler available to On to allow the boiler to be part of
the staging sequence . Select Off if the boiler is being serviced
or that boiler output is not used .
Boiler Fuel
Select the type of fuel used by the boiler .
Fire Delay
The Fire Delay is the ignition delay time of the boiler, from
when the boiler enable contact is closed until when a flame is
established . The Fire Delay can be found in the boiler manual
or can be timed with a watch .
Boiler High Output
The control tracks the approximate amount of energy used .
The maximum boiler output is entered in units of MBTU/hr . 1
MBTU / hr = 1,000 Btu per hour . The range is from 10 to 9990
MBTU/hr .
Single Boiler Operation
The control turns on boiler 1 whenever in the Establishing
Steam or Heat On phases of a heating cycle or when there is
a DHW call .
Combustion Air Post Purge
There is a fixed 15 second post purge of the Combustion Air
Damper relay after the last boiler has turned off .
Two Boiler Operation
The lead boiler turns on whenever in the Establishing Steam
or Heat On phases of a heating . The lag boiler operates based
upon the system steam pressure . The lag boiler:
• Turns on when the pressure falls the Stage 2 Differential
below the Pressure Target and the Stage Delay elapses
• Turns off when the pressure reaches the Pressure Target
Rotation
The Rotate feature changes the firing order of the boilers
whenever one boiler accumulates 48 hours more run time than
any other boiler . After each rotation, the boiler with the least
running hours is the first to fire and the boiler with the most
running hours is the last to fire . This function ensures that the
boilers receive equal amounts of use . When Rotation is Off, the
firing sequence always begins with boiler 1 .
1
720 hours
2
672 hours
31
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