33
3) Thereturnpipingmaybeconnectedintotheboilerthroughthebackorsidesoftheboilerbyrotatingthedrainelbowand
routingthereturnpipingthroughtheappropriateknockout.
4) Circulator(Required)-UsuallyatleasttwocirculatorswillberequiredtoproperlyinstallaCHGSeriesboiler.Seeprevious
section(SystemDesign)forinformationonsizingthecirculators.
5) ExpansionTank(Required)-Ifthisboilerisreplacinganexistingboilerwithnootherchangesinthesystem,theold
expansiontankcangenerallybereused.Iftheexpansiontankmustbereplaced,consulttheexpansiontankmanufacturer’s
literatureforpropersizing.
6) FillValve(Required)-Eitheramanualorautomaticllvalvemaybeused.Theideallocationforthellisattheexpansion
tank.
7) AutomaticAirVent(Required)-Atleastoneautomaticairventisrequired.Manualventswillusuallyberequiredinother
partsofthesystemtoremoveairduringinitialll.
8) ManualResetHighLimit(Requiredbysomecodes)-ThiscontrolisrequiredbyASMECSD-1andsomeothercodes.
Installthehighlimitintheboilersupplypipingjustabovetheboilerwithnointerveningvalves.Setthemanualresethigh
limitto200°F.WirethelimitperFigures9.1&9.2intheWiringsection.
9) FlowControlValve(Required)-Theowcontrolvalvepreventsowthroughthesystemunlessthe circulatorisoperating.
Flowcontrolvalvesareusedtopreventgravitycirculationor“ghostows”incirculatorzonesystemsthroughzonesthatare
notcallingforheat.
10) IsolationValves(Recommended)-Isolationvalvesareusefulwhentheboilermustbedrained,astheywilleliminatehaving
todrainandrelltheentiresystem.
11) DrainValve(Required)-Thedrainvalveisinstalledonthereturnteelocatedinthelowervestibulecompartmentasshownin
Figure8.2.
12) LowWaterCut-off(Required)-Thelowwatercut-offsuppliedwiththisboilermustnotberemoved.
D. Piping for Special Situations
1) Systemscontainingoxygen-Manyhydronicsystemscontainenoughdissolvedoxygentocauseseverecorrosiondamageto
analuminumboilersuchastheCHG.Someexamplesinclude:
• Radiantsystemsthatemploytubingwithoutanoxygenbarrier.
• Systemswithroutineadditionsoffreshwater.
• Systemswhichareopentotheatmosphere.
 Iftheboileristobeusedinsuchasystem,itmustbeseparatedfromtheoxygenatedwaterbeingheatedwithaheat
exchangerasshowninFigure8.13.Consulttheheatexchangermanufacturerforproperheatexchangersizingaswellas
owandtemperaturerequirements.Allcomponentsontheoxygenatedsideoftheheatexchanger,suchasthepumpand
expansiontank,mustbedesignedforuseinoxygenatedwater.
2) PipingwithaChiller-Iftheboilerisusedinconjunctionwithachiller,pipetheboilerandchillerinparallelasshownin
Figure8.14.Useisolationvalvestopreventchilledwaterfromenteringtheboiler.
3) AirHandlers-Wheretheboilerisconnectedtoairhandlersthroughwhichrefrigeratedairpasses,useowcontrolvalvesin
theboilerpipingorotherautomaticmeanstopreventgravitycirculationduringthecoolingcycle.