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 2 page image

2INSTALLATIONStep 1 — Provide Unit SupportROOF CURB — Assemble or install accessory roof curb inaccordance with instructions shipped with this accessory. SeeFig. 1. Install insulation, cant strips, roofing, and counter flash-ing as shown. Ductwork can be installed to roof curb beforeunit is set in place. Ductwork must be attached to curb and notto the unit. Curb must be level. This is necessary to permit unitdrain to function properly. Unit leveling tolerance is ± 1/16 in.per linear ft in any direction. Refer to Accessory Roof Curb In-stallation Instructions for additional information as required.When accessory roof curb is used, unit may be installed onclass A, B, or C roof covering material. Carrier roof curb acces-sories are for flat roofs or slab mounting.ALTERNATE UNIT SUPPORT — When a curb cannot beused, install unit on a noncombustible surface. Support unitwith sleepers, using unit curb support area. If sleepers cannotbe used, support long sides of unit with a minimum of 3 equal-ly spaced 4-in. x 4-in. pads on each side.SLAB MOUNT (Horizontal Units Only) — Provide a levelconcrete slab that extends a minimum of 6 in. beyond unit cab-inet. Install a gravel apron in front of condenser coil air inlet toprevent grass and foliage from obstructing airflow.NOTE: Horizontal units may be installed on a roof curb ifrequired.Step 2 — Remove Shipping Rails — Remove ship-ping rails prior to lowering unit onto roof curb. See Fig. 2. Therails are attached to the unit at both the return end and condens-er end. Remove the screws from both ends of each rail. Becareful not to drop the rails onto any surface that could bedamaged. Discard the rails. It is important to replace the screwsinto the unit to avoid any air or water leakage.Step 3 — Rig and Place Unit — Inspect unit for trans-portation damage. See Tables 1-3 for physical data. File anyclaim with transportation agency.Do not drop unit; keep upright. Use spreader bars over unitto prevent sling or cable damage. Rollers may be used to moveunit across a roof. Level by using unit frame as a reference;leveling tolerance is ± 1/16 in. per linear ft in any direction. SeeFig. 3 for additional information. Unit rigging weight is shownin Fig. 3.Four lifting holes are provided in the unit base rails asshown in Fig. 3. Refer to rigging instructions on unit.POSITIONING — Maintain clearance, per Fig. 4, around andabove unit to provide minimum distance from combustiblematerials, proper airflow, and service access.Do not install unit in an indoor location. Do not locate airinlets near exhaust vents or other sources of contaminated air.For proper unit operation, adequate combustion and ventilationair must be provided in accordance with Section 5.3 (Air forCombustion and Ventilation) of the National Fuel Gas Code,ANSI Z223.1 (American National Standards Institute).Although unit is weatherproof, guard against water fromhigher level runoff and overhangs.Locate mechanical draft system flue assembly at least 4 ftfrom any opening through which combustion products couldenter the building, and at least 4 ft from any adjacent building(or per local codes). When unit is located adjacent to publicwalkways, flue assembly must be at least 7 ft above grade.ROOF MOUNT — Check building codes for weight distribu-tion requirements. Unit operating weight is shown in Table 1.INSTALLATION ONTO CURB — The 48PG units are de-signed to fit on either the accessory full perimeter curb. Correctplacement of the unit onto the curb is critical to operating per-formance. To aid in correct positioning, 3/8-in. diameter locat-ing holes have been added to the unit base rails. When placingthe unit, these holes should line up with the roof curb edge asshown in Fig. 5 and 6, to assure proper duct opening alignment.For placement on the roof curb, use the alignment holes locatedapproximately 2-in. from the end of the base rail on the returnend of the unit. See labels on the side of the unit for moredetails.Disconnect gas piping from unit when pressure testing atpressure greater than 0.5 psig. Pressures greater than0.5 psig will cause gas valve damage resulting in hazardouscondition. If gas valve is subjected to pressure greater than0.5 psig, it must be replaced before use. When pressuretesting field-supplied gas piping at pressures of 0.5 psig orless, a unit connected to such piping must be isolated byclosing the manual gas valve(s).IMPORTANT: Units have high ambient operating limits. Iflimits are exceeded, the units will automatically lock thecompressor out of operation. Manual reset will be requiredto restart the compressor.IMPORTANT: The gasketing of the unit to the roof curb iscritical for a watertight seal. Install gasket with the roofcurb as shown in Fig. 1. Improperly applied gasket can alsoresult in air leaks and poor unit performance. Do not slideunit to position on roof curb.Do not allow the shipping rail to drop on the roof surface.Damage to the roof surface may result.All panels must be in place when rigging. Unit is notdesigned for handling by fork truck. Damage to unit mayresult.Do not slide unit to position it when it is sitting on the curb.Curb gasketing material may be damaged and leaks mayresult.