Crown Bermuda Installation Manual

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BSI Control System – Sequence of Operation
(RefertoFigures16&17forladderandconnectiondiagrams)
Sequence of Operation, Intermittent Ignition
1)Whentheboilerisenergized,24voltsisimmediatelyappliedtoterminals“1”(blue)and“4”(yellow)ontheventdamp-
er.Assumingthatthereisnocallforheat,andthatthedamperswitchisinthe“automatic”position,thedamperwillclose.
OnboilersequippedwithHydrolevelCG400Aprobetypelowwatercut-offs,voltageisalsoalwaysappliedtoterminals“1”
(blue)and“2”(yellow)onthelowwatercut-offtopowerthewaterlevelsensingcircuit.Onboilersequippedwith#67oat
typelowwatercut-offs,powerisalwaysappliedtoterminal“2”onthe#67LWCO.
2)Assumingthatwaterisabovethecut-offlevel,powerwillappearatterminal“3”ontheCG400LWCOorterminal“1”
onthe#67LWCO.
3)Assumingthatsteampressureisbelowthepressurelimitsetting,powerwillappearononesideofrelaycontact1R1
(Graylead).Relay1RistheR8225mountedunderthejunctionbox.
4) Acallforheatfromthethermostatenergizesrelaycoil1Rcausingcontacts1R1tomake.Currentthenowsthrough
contacts1R1topinterminal“2”(orange)attheventdamperandthedamperopens.
5) Oncetheventdamperisfullyopen,anendswitchinsidethedamperwillmake,energizingpin“3”(red)atthedamper.
6) Currentpassesfromterminal“3”ontheventdamperthoughtheamerolloutandblockedvent(“spill”)switches.Under
normalconditions,bothoftheseswitchesaremadeandvoltagewillthereforeimmediatelyappearacrossterminals“24V”
and“24V(GND)”ontheignitionmodule.
7) Uponapplicationofvoltageacrossthe“24V”and“24V(GND)”terminals,theignitionmodulewillstartanignition
sparkatthepilotandapply24voltsacrossthepilotvalve(terminals“PV”and“MV/PV”).
8) Oncethepilotisestablished,thepilotamewillactasadiode,convertingtheACcurrentattheelectrodetoahalfwave
DCcurrentatthepilot’sgroundstrap.ThisDCcurrentowsthroughtheboilertothe“GND(BURNER)”connectiononthe
ignitionmodule.Fortheignitionmoduletorecognizethatapilotameispresent,theDCcurrentowingintothisterminal
mustbeinexcessofapproximately1.0uA.
9) Oncetheignitionmoduledetectsthepresenceofapilotame,voltageisappliedacrossthemainvalve(terminals“MV”
and“MV/PV”),openingthevalveandestablishingmainame.
10) Thewayinwhichtheignitionmodulehandlesfailuretoestablishpilotorthelossofanalreadyestablishedpilotdepends
upontheexactignitionmodulesuppliedwiththeboiler.Formoreinformationonmoduleoperation,consulttheignitionmod-
uleinstructionssuppliedwiththeboilerorthelocalCrownrepresentative.
Safety Control Operation - Intermittent Ignition
HydrolevelCG400ALowWaterCut-off-Interruptsburneroperationifthewaterintheboilerdropsbelowasafelevel.Asthe
waterdropspastthecut-offpoint,theamberlampontheCG400willglow.TheCG400willinterruptpowertotheburners15sec-
ondsafterthewaterleveldropspastthecut-offpoint.Thisfeaturepreventsshortcyclingoftheburnersduetoabouncingwater
line.Theburnerswillthenremainoffuntil30secondsafterthewaterlevelhasbeenraisedabovethecut-offpoint.
TheCG400isalsoequippedwithafeaturewhichwillshutdowntheburnersaftertheyhavebeenringfor10minutes,regard-
lessofthewaterlevelstatus.TheCG400thenkeepstheburnersofffor90seconds,allowingthewaterlevelandanyfoamwhich
ispresenttosettle.Duringthis90secondinterval,thegreenLEDontheCG400willglow.Ifthewaterlevelisstillabovethecut-
offlineattheendofthis90secondinterval,theCG400willrestarttheburners.
Theventdamperwillclosewhenthelowwatercut-offinterruptsburneroperation.
McDonnell&Miller#67LowWaterCut-off-Interruptsburneroperationifthewaterintheboilerdropsbelowasafelevel.
Burneroperationisrestoredwhenthewaterlevelintheboilerisraisedabovethecut-offpoint.
Theventdamperwillclosewhenthelowwatercut-offinterruptsburneroperation.
PressureLimitControl-Interruptsburneroperationwhenthepressureintheboilerexceedsthe“Cut-in”settingplusthediffer-
entialsetting.The“Cut-in”settingisshownontheoutsideofthecontrolandisadjustedusingthescrewonthetopofthecontrol.
Thedifferentialisadjustedusingthewhitethumbwheelontheinsideofthecontrol.Burneroperationisrestoredwhenthepres-
sureintheboilerdropstothe“Cut-in”pressure.
Theventdamperwillclosewhenthepressurelimitcontrolinterruptsburneroperation.