Sequence Of Operation - Lochinvar 150 - 500 Installation & Operation Manual

11
Operating information

Sequence of operation

OPERATION
1. Upon a call for heat, the control turns on the water heater pump.
2. The control connects 120 VAC to the blower. The blower does not
run at this time.
• The flow switch must close before the control powers up the
blower.
• The manual reset high limit must be closed before the control
powers up the blower.
• If the unit is equipped with a solenoid valve and/or a vent
valve, they will be energized along with the blower.
• 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.
3. The control then starts a 10 second prepurge cycle.
4. Once the prepurge cycle is complete,
switch 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.
5. If the control does not detect flame by the end of the trial for
ignition, the control performs a 10 second postpurge, another
prepurge and tries to light the burner again. If the burner does
not light after 4 trials (1 trial on the 500 model), the control locks
out for 1 hour and then tries another set of 4 trials, except on
the 500 model which is manual reset lockout.
6. If the control detects a flame before the trial for ignition ends, it
begins to modulate the burner in order to maintain the set point.
7. Once the call for heat is satisfied, the control will turn off the burner.
The blower will remain on for the 10 second postpurge cycle. The
water heater pump will continue to run for its respective pump
delay time, then turn off.
8. Water heater pump off.
(continued)
WHR: Standby
OUT: 123.8F(129)
WHR: Standby
OUT: 123.8F(129)
WHR: PREPURGE
OUT: 123.9F(129)
and the blocked drain
WHR: IGNITION
OUT: 123.9F(129)
WHR: POSTPURGE, PREPURGE
OUT: 123.9F(129)
WHR: RUN 20% RATE
OUT: 124.8F(129)
WHR: POSTPURGE
OUT: 127.4F(129)
WHR: Standby
OUT: 124.7F(129)
Installation & Operation Manual
DISPLAY
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