Lochinvar KNIGHT 399 - 800 - Manual (Page 60)

Installation & Operation Manual
60
11
Operating information
Sequence of operation
OPERATION DISPLAY
1. Upon a call for heat, the control turns on the appropriate pumps
(system and boiler pumps for space heating call; DHW pump
for DHW call).
BLR: Standby
OUT: 123.8F(129)
2. The control connects 120 VAC to the blower. The blower
does not run at this time.
• The manual reset high limit must be closed and reset.
• Once the pumps are turned on, the flow switch must close.
• If the unit is equipped with gas pressure switches, they must
close.
• If an auxiliary limit is connected to the unit, it must close.
• The air pressure switch must be closed.
BLR: Standby
OUT: 123.8F(129)
3. The control then starts a 15 second prepurge cycle.
BLR: PREPURGE
OUT: 123.9F(129)
4. Once the prepurge cycle is complete, and the blocked drain
switch is closed, the control starts the 4 second trial for ignition
by sending spark voltage to the spark electrode and opening
the gas valve.
BLR: IGNITION
OUT: 123.9F(129)
5. If the control does not detect flame before the trial for ignition
ends, the control will perform a 10 second postpurge. The 399
model will start another prepurge and trial for ignition. If the
burner does not light after 4 trials on the 399 model, the control
will lock out for one hour and then try again.
On the 500 - 800 models, the control will lock out indefinitely
after the first two trials for ignition fail.
BLR: POSTPURGE, PREPURGE
OUT: 123.9F(129)
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.
If the boiler lights due to a space heating call for heat, and the
ramp delay function is active (default is off), the modulation
will be held to a series of increasing limits after the burner has lit.
BLR: SH 20% RATE
OUT: 124.8F(129)
7. If the space heating call for heat is active, and the DHW
thermostat or sensor starts a DHW call for heat, the control will
turn on the DHW pump, wait 2 seconds, and then turn off the
boiler pump. This will divert the hot water away from the
heating zone(s) and send it to the DHW tank instead. The
control will then modulate to maintain the outlet temperature to
the DHW boiler set point.
BLR: DHW 85% RATE
OUT: 177.8(180)
8. If the boiler is not part of a cascade, and the DHW call for heat
remains active for more than 30 minutes, and the space heating
call for heat is also active, then the control will turn on the boiler
pump, turn off the DHW pump after 2 seconds, and resume
modulating based on the space heating set point. As long as
both the space heating and DHW calls for heat remain active,
the control will switch back and forth between the two modes
until one of them is satisfied.
BLR: SH 41% RATE
OUT: 123.0F(129)
9. Once both calls for heat are satisfied, the control will turn off the
burner. The blower will remain on for the 10 second postpurge
cycle. Any pumps that are running will continue to run for their
respective pump delay times, then turn off.
BLR: POSTPURGE
OUT: 127.4F(129)
10. Boiler pump off, system pump continues its delay if longer.
BLR: Standby
OUT: 124.7F(129)
11. System pump off.
BLR: Standby
OUT: 122.9F(129)