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1 Service
Table 1-1 (continued from previous page) Sequence of Operation
OPERATION DISPLAY
8. If the space heating call for heat is active, and the tank thermostat
or sensor starts a DHW call for heat, the boiler will switch to the
DHW mode. If programmed for normal DHW operation (not as a
zone), the DHW pump will turn on first, then the boiler pump will
turn off 2 seconds later. This will divert the boiler’s outlet water
from the heating system and send it to the tank coil instead. The
control will then modulate to maintain the outlet temperature to
the DHW boiler set point.
9. If the boiler is not part of a Cascade, and both the space heating
and DHW calls for heat remain active long enough, the boiler will
switch back and forth between the two heating modes until one
of them is satisfied.
10. Once both calls for heat are satisfied, the control will turn off the
burner. The blower will continue to run during a 10 second
postpurge.
11. Any pumps that are running will continue to run for their
respective pump delay times before turning off, unless
programmed to remain on continuously. A 60 second anti-cycle
period will start, which will delay any new call for heat until it
times out.
12. In Standby, ready to start a new cycle.
Service Manual