CSVB Series II - Columbia Heating

Sequence of Operation -See Figure 12, Page 231. Thermostat calls for heat, control relay contacts.2. Circulator pump is powered through terminals C1 andC2. Control holds off burner and attempts to satisfythermostat with residual boiler heat.3. Induced draft blower and transformer primary arepowered.4. When blower gets up to speed and blower suctionpressure reaches pressure switch set point, pressureswitch contacts close sending 24 volts to pilot controlfrom transformer secondary.5. Pilot gas valve opens and spark initiates to light pilotburner.6. When pilot flame is proven, spark drops out.7. Main gas valve opens and pilot burner ignites mainburners.8. If boiler water temperature reaches high limit setpoint, high limit contacts open, cutting power toblower and pilot control. Burners extinguish and blowerstops. Circulator pump continues to run as long asthe thermostat continues to call for heat. When boilerwater temperature drops past the high limit set pointand through the differential, high limit contacts close,repeating steps 3-7.9. If venting system becomes blocked, blower suctionpressure will drop below pressure switch set point,opening pressure switch contacts and cutting power topilot control. Burners will extinguish, but blower willremain powered as long as thermostat continues to callfor heat. If venting system clears, steps 4-7 will repeat.10. Thermostat is satisfied, ending call for heat. Relay coilis de-energized, opening contacts. Burners extinguish.Blower and circulator pump stop.SEQUENCE OF OPERATION22