installation, operating and service instructions eva series boiler
installation, operating and service instructions eva series boiler
installation, operating and service instructions eva series boiler
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NORMAL SEQUENCE OF OPERATION<br />
Boiler in St<strong>and</strong>by<br />
Limits <strong>and</strong> <strong>operating</strong> controls such as safety <strong>and</strong> <strong>operating</strong> temperature limits,<br />
water flow switch, thermal fuse switches <strong>and</strong> high/low gas pressure switch<br />
contacts must be closed to initiate <strong>and</strong> continue burner sequence. Flame<br />
signal must not be present. Airflow switch must be open.<br />
Call for Heat<br />
Control terminal 5 is energized <strong>and</strong> all safety <strong>and</strong> <strong>operating</strong> control contacts<br />
are closed. Control terminal 4 is energized to start the combustion air fan.<br />
Combustion Air Flow Switch<br />
Contacts Make<br />
Contacts close when fan generates enough differential air pressure to actuate<br />
combustion air flow switch diaphragm.<br />
Prepurge Begins<br />
Fan purges combustion chamber <strong>and</strong> venting for 30 seconds.<br />
30 sec.<br />
Pilot Flame Establishing<br />
Period Begins<br />
5 sec.<br />
Early Spark Termination<br />
Pilot gas valve(s) <strong>and</strong> ignition transformer are energized. Pilot gas flows to<br />
pilot burner <strong>and</strong> is ignited.<br />
Ignition transformer is de-energized after 5 seconds. Presence of pilot flame<br />
is detected by ultraviolet scanner. Flame signal exceeds 1.5 volts DC.<br />
5 sec.<br />
Main Flame Establishing<br />
Period Begins<br />
Main gas valves are energized. Gas flows to main burner <strong>and</strong> is ignited by<br />
pilot flame. Pilot <strong>and</strong> main flames are detected by ultraviolet scanner. Flame<br />
signal continues to maintain 1.5 to 5.0 volts DC.<br />
3 sec.<br />
Run Period Begins<br />
After 5 seconds, pilot gas valve(s) is de-energized. Gas flow to pilot stops.<br />
Pilot flame is extinguished. Main flame is detected by ultraviolet scanner.<br />
Flame signal continues to maintain 1.5 to 5.0 volts DC.<br />
Run Period<br />
Main burner continues to operate until call for heat ends, contacts of a safety<br />
or <strong>operating</strong> control open, electrical power is interrupted, or the flame signal<br />
drops below 1.5 volts DC. 2-Stage <strong>and</strong> Modulating <strong>boiler</strong>s operate based<br />
on the load, determined by the difference between the bulk <strong>boiler</strong> water<br />
temperature <strong>and</strong> the <strong>boiler</strong> water set point.<br />
Post Purge<br />
Main gas valves are de-energized. Gas flow to main burner stops. Main<br />
flame is extinguished. Fan continues to operate for 60 seconds to <strong>eva</strong>cuate<br />
combustion chamber <strong>and</strong> venting.<br />
St<strong>and</strong>by<br />
After 60 seconds fan stops.<br />
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