|
|
| Service Manual | |
|
|
|
|
|
1 Service (continued) |
|
|
| |
Sequence of operation |
|
|
| |
Table 1A Sequence of operation |
|
|
| |
|
|
|
| |
OPERATION |
| DISPLAY |
| |
|
|
| ||
1. Upon a call for heat, the control turns on the water heater pump. | WHR: Standby |
| ||
|
| OUT: 123.8F(129) |
| |
2. The control connects 120 VAC to the blower. The blower does not |
|
|
| |
run at this time. |
|
|
| |
• If the unit is equipped with a flow switch, it must close before the |
|
|
| |
control powers up the blower. |
|
|
| |
• The manual reset high limit must be closed before the control | WHR: Standby |
| ||
powers up the blower. |
| |||
OUT: 123.8F(129) |
| |||
• 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. | WHR: PREPURGE |
| ||
|
| OUT: 123.9F(129) |
| |
4. Once the prepurge cycle is complete, and the blocked drain | WHR: IGNITION |
| ||
switch is closed, the control starts the 5 second trial for ignition by |
| |||
sending spark voltage to the spark electrode and opening the gas | OUT: 123.9F(129) |
| ||
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 | WHR: POSTPURGE, PREPURGE |
| ||
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: 123.9F(129) |
| ||
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 | WHR: WHR 20% RATE |
| ||
begins to modulate the burner in order to maintain the set point. |
| |||
|
| OUT: 124.8F(129) |
| |
|
|
|
| |
7. Once the call for heat is satisfied, the control will turn off the burner. | WHR: POSTPURGE |
| ||
The blower will remain on for the 10 second postpurge cycle. The |
| |||
water heater pump will continue to run for its pump delay time, | OUT: 127.4F(129) |
| ||
then turn off. |
| |||
|
|
| ||
8. Water heater pump off. | WHR: Standby |
| ||
|
| OUT: 124.7F(129) |
| |
9
