Carrier SINGLE PACKAGE ROOFTOP UNITS 48PG20-28 Installation And Service Instructions Manual

Also see for 48PG20---28: User's information manual User's information manual Controls, start-up, operation, service and troubleshooting instructions

Carrier SINGLE PACKAGE ROOFTOP UNITS 48PG20-28 Installation And Service Instructions Manual Manual pdf 9 page image

9Step 4 — Field Fabricate Ductwork — On verticalunits, secure all ducts to roof curb and building structure. Donot connect ductwork to unit. For horizontal applications, field-supplied flanges should be attached to horizontal dischargeopenings and all ductwork secured to the flanges. Insulate andweatherproof all external ductwork, joints, and roof openingswith counter flashing and mastic in accordance with applicablecodes.Ducts passing through an unconditioned space must beinsulated and covered with a vapor barrier.If a plenum return is used on a vertical unit, the returnshould be ducted through the roof deck to comply with applica-ble fire codes.A minimum clearance is not required around ductwork.Cabinet return-air static shall not exceed –0.35 in. wg witheconomizer or 0.45 in. wg without economizer.These units are designed for a minimum continuous return-air temperature in heating of 50 F (dry bulb), or an intermittentoperation down to 45 F (dry bulb), such as when used with anight set-back thermostat.To operate at lower return-air temperatures, a field-suppliedoutdoor-air temperature control must be used to initiate bothstages of heat when the temperature is below 45 F. Indoor com-fort may be compromised when these lower air temperaturesare used with insufficient heating temperature rise.Step 5 — Make Unit Duct ConnectionsVERTICAL CONFIGURATION — Unit is shipped for ver-tical supply and return duct connections. Ductwork openingsare shown in Fig. 1 and 4. Duct connections for verticalconfiguration are shown in Fig. 7. Field-fabricated concentricductwork may be connected as shown in Fig. 8 and 9. The unitis designed to attach the ductwork to the roof curb. Do notattach duct directly to the unit.HORIZONTAL APPLICATIONS — Horizontal units areshipped with outer panels that allow for side by side horizontalduct connections. If specified during ordering, the unit will beshipped with the vertical duct openings blocked off from thefactory, ready for side supply installation. If the horizontalsupply/return option was not specified at time of ordering theunit, a field-installed accessory kit is required to convert thevertical unit into a horizontal supply configuration.Installation of the duct block-off covers should be complet-ed prior to placing the unit unless sufficient side clearance isavailable. A minimum of 66 in. is required between the unitand any obstruction to install the duct block-off covers. Sidesupply duct dimensions and locations are shown on Fig. 4.Install ductwork to horizontal duct flange connections on sideof unit.For vertical supply and return units, tools or parts coulddrop into ductwork and cause an injury. Install a 90 degreeturn in the return ductwork between the unit and the condi-tioned space. If a 90 degree elbow cannot be installed, thena grille of sufficient strength and density should be installedto prevent objects from falling into the conditioned space.SEENOTE SEENOTEAIROUTAIRINHEATEXCHANGERECONOMIZERSEENOTESEENOTEAIR OUTAIR INHEATEXCHANGERAIR OUTECONOMIZERNOTE: Do not drill in this area; damage to basepan may result inwater leak.Fig. 7 — Air Distribution — Vertical Supply/ReturnNOTE: Do not drill in this area; damage to basepan may result inwater leak.Fig. 8 — Air Distribution — Concentric DuctALIGNMENTHOLE SHOULDLINE UP WITHROOF CURBEDGE FLANGEEDGE FLANGEALIGNMENTHOLE(IN BASE RAIL)Fig. 5 — Alignment Hole DetailsSUPPLYOPENINGRETURNOPENINGROOF CURBCURBSUPPLYOPENINGCURBRETURNOPENINGALIGNMENTHOLES FORCURB-BOTHSIDESFig. 6 — Alignment Hole Location