Burnham FCM120 Specifications download pdf (Page 64)

XII Operation

1) TheFCMboilerusesamicroprocessorbasedcontrol,knownasa“MCBA”,tomanageallboilerfunctions 

includingamesupervisionandmodulation.Twosetpointor“target”boilersupplytemperaturesarestoredinthe

MCBA’smemory;oneforspaceheatingandonefordomesticwaterproduction.Ifanoutdoortemperaturesensor

isconnectedtotheboiler,thespaceheatingsupplysetpointwillautomaticallyadjustdownwardsastheoutdoor

temperatureincreases.Formoreinformationonthisfeatureseethediscussiononboilerwaterresetbelow.

 TheMCBAmodulatestheboilerinputbyvaryingthefanspeed.Asthefanspeedincreases,sodoesthe 

amountofgasdrawnintotheblower.Asaresult,afairlyconstantair-fuelratioismaintainedacrossallinputs. 

 TheMCBAdeterminestheinputneededbylookingatbothcurrentandrecentdifferencesbetweenthesupply 

temperatureandthesetpointtemperature.Asthesupplytemperatureapproachesthesetpointtemperature,thefanwill

slowdownandtheinputdrop.Dependingonthemodelboiler,theminimuminputisbetween¼and1/5ofmaximum

input.

 TheMCBAalsomonitorsboilerreturnanduetemperatures.Inaddition,allothersafetycontrols,includingthelow

watercut-offandsafetylimit,areconnectedintotheMCBA.TheMCBAusesinputfromallofthesecontrolstoeither

shutdowntheboilerwhenanunsafeconditionexistsor,insomecases,tocorrecttheproblem.

2) Thedisplaypanelhasthreeprimarymodesofoperation.Theseare:

• StandbyMode–Displaysboiler’scurrentstatus.Thisisthedefaultoperatingmode.

• ParameterMode–Usedtochangecontrolsettings

• InformationMode–Displaysboileroperatingtemperatures

 Undernormalconditions,theboilerisinstandbymodeandthedisplaylookslikethatshowninFigure12.1.Thethree

digitstotherightofthedecimalpointaretheboiler’ssupplytemperature.Thedigittotheleftofthedecimalpointisthe

boiler’sstatuscode.Alistofstatuscodes,andtheirmeanings,isshowninTable12.3.

 Figure12.2isamapofthemenustructureforthecontrolpanel.Pushthemodekeytomovefromonemodetothenext.

Asyouchangemodes,themodeyouareenteringisshownonthedisplay:

a) “PArA”

forParameterMode

b) “Info”forInformationMode

c) “Stby”forStandbyMode.Uponenteringstandbymode,“Stby”willbrieyappearonthedisplayandthenthe

display willshowtheboiler’sstatusalongwiththesupplytemperature(Figure12.1).

Thecontrolwillreturntostandbymodefromanyothermodeifnokeyispressedfor20minutes.

Figure 12.1: Normal Display In Standby Mode

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Burnham FCM120 Specifications Page 64