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.
