1.
Standby
Burner off
Circulator off
2.
Circulator Pre-purge
Burner off
Circulator on
1. The boiler has not detected a call for heat (tt = off and dh = off.
Check that the thermostat:
When a thermostat call for heat is detected control display “tt” will show “on”
Make sure thermostat is calling for heat and contacts (including appropriate zone controls) are closed.
Check for loose connection.
Check the DHW demand:
When a domestic call for heat is detected “dh” will show “on”
Make sure the DHW aquastat contact is closed. Check for loose connection.
2. The boiler is warm and circulator is providing residual boiler heat to building:
Check boiler temperature
The boiler will not start until boiler water temperature is less than the Setpoint (SP) minus differential (df)
If boiler water temperature is higher than Start Temperature (ST_, default = 140 F) and the Circulator Prepurge (PP_, default = 2 minutes) time has not expired, boiler start will be delayed until water temperature drops or time expires. To permit the boiler to start sooner increase Start Temperature parameter.
