1 Service (continued)
Sequence of operation
Table 1A_Sequence of Operation - Space Heating and DHW
OPERATION | DISPLAY |
|
|
1. The manual reset high limit must be closed before any | HTR: Standby |
action will take place. | OUT: 123.8F(129) |
|
2.Upon a call for heat the control turns on the appropriate HTR: Standby
pumps (system and boiler pumps for space heating; DHW OUT: 123.8F(129) pump for DHW call). The flow switch and low water cutoff
(if equipped) must close.
3.• The gas pressure switch(es) (if equipped) must close.
• The louver proving input must close. | HTR: Standby |
• If the air pressure switch is open, the prepurge cycle then | |
begins by starting the combustion blower. Once started, | OUT: 123.8F(129) |
the air pressure switch must close. |
|
4. After the 15 second prepurge, the blower slows down and | HTR: PREPURGE | ||
| the hot surface igniter (HSI) is energized. The HSI is heated | ||
| for at least 20 seconds. |
| OUT: 123.9F(129) |
5. | Once the HSI is hot, the trial for ignition begins with the | HTR: IGNITION | |
| opening of the gas valve. |
| OUT: 123.9F(129) |
|
|
| |
6. | If the SMART SYSTEM control does not sense flame, then | HTR: POSTPURGE, PREPURGE | |
| it will lock out. |
| OUT: 123.9F(129) |
|
|
|
|
7. | If the SMART SYSTEM control senses | flame, | HTR: RUN STG: 1 |
| it will fire the burner to maintain the setpoint. | The | |
| stages will fire as required to hold the actual temperature at | OUT: 124.8F(129) | |
| the setpoint. |
|
|
8.If the space heating call for heat is active, and the DHW thermostat closes, the control will turn on the DHW pump,
wait 2 seconds, and then turn off the boiler pump. This will HTR: DHW STG 123
divert the hot water away from the heating zone(s) and send OUT: 177.8(180) it to the DHW tank instead. The control will then fire the
stages to maintain the outlet temperature to the DHW boiler setpoint.
9
