Sequence Of Operation - Lochinvar EcoShield SHW60-325CE Installation, Commissioning And Maintenance Instructions

12.3

SEQUENCE OF OPERATION

OPERATION
Upon a call for heat, the control turns on the appropriate
1.
pumps.
The control connects 230 VAC to the fan. The fan does
2.
not run at this time.

If the unit is equipped with a flow switch or low
water cut-off, it must close before the control
powers up the fan.

If the unit is equipped with a manual reset high
limit it must be closed before the control powers
up the fan.

If the unit is equipped with a gas pressure switch,
it must close at this time.

If there is an auxiliary device connected to the
unit, the unit will then provide 24 VAC to its enable
relay. If the auxiliary device has a proving switch,
it must close before the sequence continues.
The control then starts a 10 second prepurge cycle.
3.
Once the prepurge cycle is complete, and the blocked
4.
drain and auto-reset high limit are closed, the control
starts the 5-second trial for ignition by sending spark
voltage to the spark electrode and opening the gas
valve.
If the control does not detect flame by the end of the
5.
trial for ignition, the control performs a 10 second
postpurge. On the SHW45-325CE to SHW115-435CE
models, the control will perform another prepurge and
will try to light the burner again. If the burner does not
light after 4 trials, the control will lockout for 1 hour and
then try another set of 4 trials. On the SHW145-435CE
the unit will lockout until manually reset.
If the control detects a flame before the trial for ignition
6.
ends, it begins to modulate the burner in order to
maintain the set point.
Once the call for heat is satisfied, the control will turn off
7.
the burner. The fan will remain on for the 10-second
postpurge cycle. The primary pump will continue to run
for its respective pump delay time, and then turn off.
Primary pump switches off.
8.
DISPLAY
WHR: Standby
OUT: 61.4C (65)
WHR: Standby
OUT: 61.4C (65)
WHR: PREPURGE
OUT: 61.5C (65)
WHR: IGNITION
OUT: 61.5C (65)
WHR: POSTPURGE, PREPURGE
OUT: 61.5C (65)
WHR: RUN 20% RATE
OUT: 62.6C (65)
WHR: POSTPURGE
OUT: 64.5C (65)
WHR: Standby
OUT: 64.8C (65)
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