Specifications

68
d) Aftertheprepurge,thecontrolmoduleenergizesthegascontrolvalveandthesparkfor4.5seconds.Ifaameis
establishedandproved,thecontrolallowstheametostabilizefor5secondsatthecombustionfanignitionspeed
setting.Iftheamefailstoprove,thecontrolmodulewillattempttolighttheburner4moretimes.Ifaameisstill
notestablished,thecontrolwilllockout.
e) Oncetheamestabilizationperiodhasended,theMCBAallowstheburnertomodulate.Theactualringrate
isdependentuponthemeasuredcurrentandrecentdifferencesbetweenthesetpointtemperatureandthesupply
temperature.Ifanoutdoorsensorisconnectedtothecontrolmoduleandtheboilerisrespondingtoacallforheat,
thesetpointtemperaturewillbedeterminedbytheoutdoorresetcurveshowninFigure12.4.
f) Oncethesetpointtemperatureisreached,theMCBAwillturntheburneroffandallowthecombustionfantooperate
inpostpurgefor35secondsbeforeitturnsoff.
g) Thecentralheatingpumpwillcontinuetooperateuntiltheroomthermostathasbeensatised.
h) Ademandfordomestichotwater(DHW)isgivenpriorityonFCMSeriesboilers.IfacallforDHWisreceived
whiletheboilerisrespondingtoacallforheat,theheatingcirculatorisdeenergizeduntilthecallforDHWis
satised.
Figure 12.4: Outdoor Reset Curve