Williamson Series 2 - Sequence of Operation

22
Part Number 550-142-785/0812
GWI Series 2 Gas-Fired Water Boilers – Boiler Manual
Follow all procedures given in this manual and
“OperatingInstructions”whenoperatingtheboiler.
Failure to do so could result in severe personal injury,
death or substantial property damage.
1. See page 26 (or boiler “Operating Instructions” label) for
“OperatingInstructions.”
2. Raiseroomthermostattocallforheat.
a. Whileattemptingtosatisfytheheatdemand,thecontrol
module monitors the boiler temperature changes via the
temperature sensor and determines whether or not the
availablehotwaterwillsatisfythedemand,onlyrunning
thecirculator.Ifadditionalheatisneeded,thesequence
continues.WhenDHW(ifused)callsforheat,sequence
above is bypassed.
3 Blowerandcirculatorenergize.Afterpressureswitchproves
airflow, ignition control starts a 30-second prepurge.
4. Control module sparks the pilot and opens pilot valve in main
gas valve.
 a. Ifpilotdoes not light within 15 seconds, pilot valve is
closedandsparkgeneratoristurnedoff.Controlmoduleiniti-
ates a 15-second postpurge, then starts a new cycle.
 b. Ifpilotdoes light and control module senses flame cur-
rent,sparkgeneratoristurnedoffandmainvalveopens.
c. Natural Gas - Ifpilotdoesnotlightwithin15seconds,
pilotvalveisclosedandsparkgeneratoristurnedoff.Control
module waits 5 minutes, then attempts to ignite pilot again.
Thiscyclewillcontinueindenitelyifpilotignitioncontroldoes
not sense pilot flame.
5. During main burner operation:
a. Ignitioncontrolmonitorspilotame.Ifsignalislost,main
gasvalveclosesandsparkstarts.Ignitioncontrolsstarts
a flame-proving cycle as in step 5, above.
b. Ifpowerisinterrupted,mainandpilotgasvalvesclose.
Ignitioncontrolwillstartagainatstep3,left,whenpower
is restored.
6. When the water temperature limit switch opens, the blower
shutsoff,causingthepressureswitchtoopen.Theignition
control then closes the main gas valve. The circulator continues
to run.
7. Whenthethermostatopens(demandsatised),theignition
control closes pilot and main gas valves. Blower and circulator
shut down.
8 Boilerisnowintheoff(stand-by)cycle.
9. Repeatsteps1through7severaltimestoverifycontrolsare
operating correctly.
10.Returnthermostat(s)tonormalsetting.
11. Set the thermostat heat anticipator as instructed in the wiring
diagram(andonboilerwiringdiagramlabel).
9a Sequence of operation