28
controls and swItches
Thismodelisprovided���withthreepressureswitches.Theseswitches
areessentialtothesafeandproperoperationoftheunit.Allswitches
arewiredin series.Thecontrolleris setupto shuttheunitdown
wheneverthereisafailureofanyoftheswitches.Itisimportantto
understandthepurposeofeachswitch.
FIGURE 12.

Blower prover swItch

(SEEFIGURE12)
TheBlowerProverSwitch isprovidedon theheatertoverify that
thefanisoperating.Itisapositivepressureswitchwhoseelectrical
contactsarenormallyopen.When thefanincreasesthepressure
intheburner,thepressureswitchwill allowtheelectricalcontacts
toclose.Thepressureswitch isconnectedtothe burnertapbya
pieceoftygontubing. Thistubingmust beconnectedinorder for
theswitchtochangetheelectricalcontacts.Thecontrollerrequires
thattheelectricalcontactsonthisairowswitchbeopen beforeit
will allow the blower to come on.

BlocKed eXhaust swItch

(SEEFIGURE12)
TheBlockedExhaustSwitch issetup toshuttheunit offwhena
build-upofpositivepressureintheexhaustvent pipeoccurs.This
switchis a positive pressure switch that requires an increase in
pressuretochangetheelectricalcontactsfromnormallyclosed to
open.Whenthisswitchpreventstheunitfromigniting,mostlikelythe
exhaustisblockedbysomemeans.Checktoseeifthecondensate
isallowedtoowfreelyfromtheexhaustelbowandforobstructions
intheexhaust ventingandexhaustvent terminal.Alsoverifythat
theventlengthdoesnotexceedthemaximumallowedasshownin
the Vent Section of this manual.

BlocKed IntaKe swItch

(SEEFIGURE12)
TheBlockedIntakeSwitchissetuptoshuttheunit offwhena
build-upofnegativepressureintheintakeairpipeoccurs.This
switchisanegativepressureswitchthatrequiresanincreasein
negativepressuretochangetheelectricalcontactsfromnormally
closedtoopen.Theswitchisconnectedtothepressuretaponthe
PVCpipeconnectedtotheinletoftheblower.Whenthisswitch
preventstheunitfromigniting,mostlikelytheintakeisblocked.
Verifythatthescreenontheintakeairconnection(conventional
vent),theintakeairpipeandtermination(directventinstallations)
arefreeofobstructionsthatmaypreventairfromenteringtheunit.
Insurethescreenonintakeairconnectionhasbeenremovedon
directventinstallations,see Figure18B.Alsoverifytheintake
airpipelengthdoesnotexceedthemaximumallowedasshown
in the Vent Section of this manual.

on/off swItch

TheON/OFFSwitchisasingle-pole,single-throwrockerswitch.This
switchprovides120Vfromthelinesourcetotheheater.

cautIon

the water h eater Is p olarItY sens ItIve. Befor e
applYInG electrIcItY to thIs heater Be certaIn that
supplY neutral wIre to Ground checK IndIcates
ZERO VOLTAGE.

hot surface IGnIter

TheHotSurfaceIgniterisadevicethatignitesthemain burnerby
hightemperature(>1800°For >982°C).When120VACis applied
totheigniter,sufcientheatisgeneratedtoignitethemainburner.
Althoughimprovementshavebeenmadetostrengthentheigniter,
itisstillfragileandcaremustbetakenwhenhandlingtheigniterto
preventbreakage.