Boiler Manual - Weil-McLain

GV90+ gas-fired water boiler — Boiler ManualInstall water piping (continued)Piping snow melt systems or combinationsnow melt/space heating systemsFigure 25 Auto return temp regulation — circulatorzoningCombination snow melt/space heating systems can have return watertemperature below 60°F, and the return temperature will fluctuate. Sothese systems require automatic return water temperature as shown inFigure 25 (zone-valve zoning) or Figure 26 (circulator zoning).Select an automatic temperature control valve or motor-operated valvewhich can be adjusted to provide a return water temperature of at least60°F. Any setting higher than 60°F will also be acceptable.Zone-valve zoning — The suggested piping uses a separate circulatorfor system circulation to assure good temperature distribution in thesystem when the return water temperature is low.Circulator zoning — The GV90+ internal circulators must not beremoved. Provide a separate circulator for each zone.The return water temperature to the boiler must beat least 60°F. Provide and apply means to regulate thereturn temperature. Failure to do so can result in boilercontrol operation problems, causing possible significantproperty damage.Zoning with zone valves — Each zone in the pipingdiagrams in this section is shown with an isolation valveon each side. Substitute a memory-stop valve for one ofthese in each zone in order to use the memory-stop valvefor balancing flow as well as isolation.Provide a separate 24-volt transformer to power the zonevalves. Size the transformer to handle the total rated loadof all connected zone valves.Zoning with circulators — The GV90+ internal systemcirculator cannot be removed from the boiler for use asone of the zone circulators. It must remain as shippedfrom the factory to allow proper flow control inside theboiler. You will need a circulator for each zone. Providecirculator relays or circulator zone controller. The systemcirculator must be supplied by the installer.MINIMUMBoiler loop pipe sizeGV90+3/4GV90+5/61”1¼”Figure 26 Auto return temp regulation — zone valvezoningLegend1 Isolation valves2 Automatic air vent (with diaphragm-type expansion tank), orconnect to tank fitting (closed-type expansion tank).3 Diaphragm- or bladder-type expansion tank, if used (For closedtypeexpansion tank, pipe from top of air separator to tank fittingas in Figure 15, page 14.)4 Zone valve5 System or zone circulator6 Flow/check valve7 Hose bibb purge valve8 Boiler pressure/temperature gauge9 System supply temperature gauge10 Return temperature automatic mixing valve11 Differential pressure by-pass valve16 Cold water fill line — see Figure 15, page 14 for typical componentsMINIMUMBoiler loop pipe sizeGV90+3/4GV90+5/61”1¼”Part number 550-142-054/1211 21