Marsal Mb42 User manual

OVEN SERVICE MANUAL

MarsalDeckOvens:MB42,MB60,MB236,MB866,SD236,SD248,SD260,SD448,SD660,

SD1048,SD1060,SD866,SD10866,WF42,WF60



RETAIN THIS MANUAL FOR FUTURE REFERENCE

1



TESTINGOFCOMPONENTS



AUTOMATICSAFETYPILOTVALVE(TSII)#55127

Pilotgasissuppliedfromthemainvalveinletthroughadrilledpassagewaytothepilotburner.Pushingthe

redresetbuttontemporarilyallowsgastoflowtothepilotburnerforignitionofthepilotburnerflame.When

thebulbheatsup,themainvalveopenstoallowgastoflowtothemainburner.Theredresetbuttonisthen

released.

Ifthepilotburnerflamefailsandcannotbereactivatedthe

followingtestcanbeperformed:



Pilotburneradjustment:RefertosectiononPage3



CleanPilotburner’slimitingorificeasfollows:

Disconnectgastubingatthepilotburnerbody

Removecupshapedorificefrompilotburnerbody

Cleanorificebyblowinganyforeignmatteroutthe

orificehole.Takecarenottoenlargeorificehole.

Replacecomponentsinreverseorder.Ifthepilot

burnerstilldoesnotoperateorthemainburner

comeswithalowflame,orwillnotcomeatall,

replacetheAutomaticSafetyPilotValve(TSII)





MAINMANUALCONTROLVALVE#70380

Themainmanualcontrolvalveisasimpleballvalve.Duetoits

simplicity,failuresofthistypeofvalvearepracticallynon‐existent.

Fordifficultiesassociatedwiththiscontrol,itwouldbebestto

replacethevalve.

THERMOSTATFDTH#71880

Foranysuspectedthermostatproblemsthefollowingproceduresshouldbereviewedinthismanual:



Thermostatadjustment



Bypass(MinimumBurnerFlame)adjustment.



Thermostatcalibration.Mostthermostatfailureswillgenerallyfallintooneofthefollowingthree

categories:

Figure 1

2



Ifthermostatisinarunawayconditionandwillnotshutoffatsettemperature,replace

thethermostat.

Ifthermostatwillnotmaintaincalibrationafteradjustment,replacethermostat.

Ifthermostatbulborcapillaryarecut,bent,orunnecessarilyflattened,replace

thermostat.

(ThisisNOTcoveredunderthewarranty!)



MAINTENANCEINSTRUCTIONS



ADJUSTMENTS

Manymalfunctionsattributedtodefectivematerialorfaultyworkmanshipmayberectifiedbythe

adjustmentofpilotburners,mainburners,orthermostats.Itisthereforewisetoattempttocorrect

operationaldifficultiesthroughadjustmentratherthantheimmediatereplacementofparts.



PILOTBURNERADJUSTMENT#70101



A commonly diagnosed malfunction of the safety pilot valve is the pilot burner/flame sensing bulb

relationshipresultingfrom:



Improperdraft



Lowgaspressure.

(NaturalGas4.5”WC–PropaneGas11”WC)





Cloggedpilotburnerorificefromdirtanddebrisfromunpurgedgaslines.



Incorrectadjustmentofpilotburnerflame.



Whenworkingcorrectly,theflamemustengulfthesafetypilotprobetip



Figure 2

3



MAINBURNERADJUSTMENTS

Satisfactoryovenperformanceandburnerlifearedependentoncorrectburneradjustment.Before

shipment,burnershavebeenadjustedforproperoperationwiththetypespecifiedontheratingplate

locatedinsidethecontrolcompartmentabovethelightswitch.Iffurtheradjustmentisnecessaryproceed

asfollows:

Adjustprimaryairshutteratthefrontoftheburnercompartmenttoobtainastableandquiet

flame.

Iftoomuchprimaryairispresent,flameswillliftfromtheburnerparts.Areductionin

primaryairwillcorrectthiscondition.

Toolittleprimaryairwillcauseyellowtippingoranentireyellowflametoappear.This

conditionindicatesincompletecombustionandmaycausecarbonsootingtoappearonmetal

partsneartheflame.

Whenaflameraisesofftheburneritisimportanttodetermineifitisa“liftingflame”ora

“floatingflame”:

o“Liftingflames”risefromtheportstoburnsomedistanceabovetheports.Insome

casestheseflameswilldropbacktotheportandliftagainintermittently.Theyare

causedbytoomuchprimaryair.Decreasingtheshutteropeningwillstoplifting

flames.

o“Floatingflames”arelongandlazyinappearance,poorlydefined,quietflames

whichrollaroundthecombustionchambersometimescompletelyofftheports.

Floatingflamesresultfromtoolittlesecondaryair.Lackofsecondaryairiscaused

byincorrectventing,cloggedflueways,blockedsecondaryairinletopenings,orlack

ofnaturalroommakeupairtotheoven.



BYPASS(MINIMUMBURNERFLAME)ADJUSTMENTS

ARobertshawFDTH300°‐650°F(149°‐343°C)typethermostatisused.Thisisathrottlingtypegas

thermostatwithbypassflameadjustmentcontrol.Forbypassadjustmentproceedasfollows:

1. Preheatovento500°F(260°C).Whenthermostathasthrottledtobypasstheglameonthe

mainburnershouldhavedecreasedtoaflamenolargerthan1/8”(6mm)

2. Ifflameistoohigh,removedial,insertscrewdriverinscrewmarked“B”onthethermostatand

turnscrewclockwisetolowerflame.

3. Ifflameistoolow,removedial,insertscrewdriverinscrewmarked“B”onthethermostatand

turnscrewcounterclockwisetoincreaseflame.



4



THERMOSTATCALIBRATION

1. Attachpyrometerleadtothermostatbulbinthebakingcompartment.Ifapyrometerisnot

available,placeareliablemercurytypeoventhermometerinthecenterofthebakingdeck

(Approximately1”abovethesurface).

2. Preheattheoventoatleast400°F(204°C).

3. Whentheburnerreachesbypassorminimumflame,takethetemperaturereading.

4. Ifthetemperatureiswithin10°F(6°C)ofthethermostatsetting,donotchangethe

thermostatsettings.

5. Ifthetemperaturediffersmorethan10°F(6°C)fromthethermostatsetting,adjustthe

thermostatasfollows:

A. Pullthermostatdialstraightoffwithoutturning.

B. Holdcalibrationplateonthermostatandloosenthetwocalibrationlockscrews

untiltheplatecanbemovedwithoutmovingthecontrol.

C. Turncalibrationplatesothatpyrometerreadingissetinlinewiththeindicator

markatthe12o’clocktemperaturevariationwillbe50°F(28°C)betweenletters.

Adjustthecalibrationplateasfollows:

1. Turncalibrationplatecounterclockwiseifpyrometerorthermometer

readingishigherthanthedialreadingORclockwiseifthepyrometeror

thermometerreadingislowerthanthedialreading.

2. Holdcalibrationplateandtightentwoscrewsfirmly.

3. Replacedial.



Figure 3

5



MAINTENANCEINSTRUCTIONS



MAINBURNERREMOVAL

1. Opencombustioncompartmentdoor.

2. Removetheburnerdoorbyremovingitshinges.

3. Removetheheatshieldsbyremovingthethreescrewsthatholdittogether.

4. Removethetwoscrewsthatholdthepilotburnertothebracket.

5. Movetheentirepilotburnerassemblywithcapillaryandpilotgastubingforwardoutof

workarea.

6. Disconnectunionatmanifold.

7. Removethree(3)boltswhichholdtheburnerassemblytotheflooroftheburner

compartmentandremovetheteesupportfortheflamedeflectors.

8. Replaceburnersinreplaceorderfromremoval.

PILOTBURNERREMOVAL:#70101

1. Opencombustioncompartmentdoor.

2. Removetheburnerdoorbyremovingitshinges.

3. Removetheheatshieldsbyremovingthethreescrewsthatholdittogether.

4. Removethescrewthatholdsthepilotburnertothebracket.

5. Removethecapillarybulb.

6. Disconnectgassupplytubingfrompilotburner.

7. Replacepilotburnerinreverseorderfromremoval.

OVENLIGHTBULBREMOVAL(MBSERIESONLY)CAUTION!!Partswillbehot!

GLASS#70019–LIGHTBULB#70071–BULBHOLDER#71893

1. Openthecontroldoorandremovethescrewlocatedatthebackofthelightbox(Figure4on

nextpage).

2. Removethelightboxoutthroughthecontroldoor(Figure5onnextpage).

3. Removethelightbulbandreplacewithnewbulb.(ONLYUSE100W120VACor500W240

VACBULBS!)

MARSALOFFERSA500W240VOLTBULBTHATISALMOSTTHESAMEILLUMINATIONASA

100WBUTMOREDURABLE.

6



 

GASCONTROLANDPIPINGCONTROLSTACKASSEMBLYREMOVAL

1. Openbakingcompartmentdoorandremovethermostatbulbfromthetopofthechamber.

Slidethecapillarytubetotheleftandintothecontroldoorarea.

2. Disconnectpilottubingatsafetyvalveoncontrolstack.

3. Disconnectthethermocouplefromthesafetyvalve.

4. Disconnectupperandlowerunionsoncontrolstack.

5. Pullcontrolstackassemblyforward.

6. Replacecontrolstackinreverseorderfromremoval.

AUTOMATICSAFETYPILOTVALVE,MAINMANUALCONTROLVALVE,AND

THERMOSTATREMOVAL

1. RemoveControlStackAssembly(seeabove).

2. RemoverespectivecontrolfromControlStackAssembly.

3. ReplacenewcontrolandothercomponentsinControlStackAssemblyinreverseorder.



ATTENTION:THETSIISAFETYVALVECANBEREPLACEDBYREPLACINGTHEHEADONLY,

LEAVINGTHEBODYSTILLATTACHEDTOTHECONTROLSTACKASSEMBLY.

PRESSUREREGULATORREPLACEMENT#71881(N)OR#71882(P)

Thepressureregulatorislocatedjustabovethecontrolstackinthecontrolcompartment.Before

replacement,gasservicetothispointmustbeshutoffbeforedisconnecting.

Figure 4 Figure 5

7



OPERATIONALDIFFICULTIES&POSSIBLECAUSES

TROUBLESHOOTING

FIRST THING’S FIRST!

Checkthediameterofyourgasconnections.FlexlinesorhardplumbingMUSTBE

¾”orbigger.

AstainlesssteelfluepipeMUSTBEinstalledonallovensthatareventingintoa

hood.

AdraftdiverterMUSTBEinstalledonallovensbeingdirectlyventedintothe

ceiling.



PROBLEM

POSSIBLECAUSES

PILOTBURNERGOES

OUT

1. Pilotthermocouplenotincenterofflame.

2. Poordraftconditionssnuffoutflame(nofluepipe).

3. Toomuchdraftpullstheflameawayfromthermocouple.

4. Airfromfansorregisterblowingatfrontofoven.

5. Pilotflametoolow.

6. Pilotorificeisdirty.

7. Thermocoupleisdefective.

8. Safetypilotvalvedefective.

9. Gasleakatpilotorificefitting.

BURNERFAILSTOCOME

ONWHENPILOTISON

1. Burnervalveofflocatedjustabovethethermostat.

2. Safetyvalvedefective.

3. Thermostatoutofcalibration.

4. Thermostatisdefective.

5. Burnerorificeisplugged.

8



OVENBURNERWILLNOT

THROTTLEDOWNORGETS

TOOHOT

1. Brokencapillarytubeonthermostat.

2. Oventhermostatoutofcalibration.

3. Minimumbypassflametoohigh(lowerto1/8”)

4. Dirtunderthermostatvalveseat.

5. Thermostatdefective.

TOOMUCHBOTTOMHEAT1. Underdraftingoroverdrafting(pullingheatoutofthe

oven).

2. Temperaturetoolow.

3. Impropercalibrationorgaspressure.

NOTENOUGHTOPHEAT1. Overdrafting(pullingheatoutoftheoven).

2. Oventemperaturetoolow.

OVENWILLNOTKEEPUP

ATBUSYTIMESORTHERE

ISUNEVENCOOKING

1. Gaspressuretoolow.

2. Insufficientgasvolumeduetotoosmallgassupplylines.

3. Additionalgasregulatorsinstalled.

4. Poordraftconditions.

5. Toomuchdraftpullingheatoutoftheovens.

6. Airfromfansorregisterblowingatfrontofoven.

SOOTINGINBAKINGOR

BURNERCHAMBER

1. Airshutterspaceistoosmall.Theremustbea1/8”–

3/16”space.

2. Airshutteriscloggedwithflourdust.Cleantheair

shutteropeningwithaknifeorbrush.



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