WeatherExpert™ High-Efficiency Single-Packaged Rooftop Units 48N: Periodical Cleaning (bi-monthly)

To inspect blower wheel:

• Remove heat exchanger access panel. Shine a flashlight into opening to inspect wheel.

• If cleaning is required, remove motor and wheel assembly by removing screws holding motor mounting plate to top of combustion fan housing.

• The motor and wheel assembly will slide up and out of the fan housing. Remove the blower wheel from the motor shaft and clean with a detergent or solvent.

• Replace motor and wheel assembly. See Fig. 48.

Adjust using a wrench on the adjusting bolts:

• Loosen holddown bolts. (See Fig. 49.)

• Turn the adjusting bolts to move the motor mounting plate toward or away from the fan to loosen or tighten the belts. Make the same number of turns to each bolt.

• Retighten holddown bolts.

IMPORTANT: When installing or replacing belts, always use a complete set of new, matched belts to prevent potential vibration problems. Mixing belts often results in premature breakage of the new belts.

• Turn off unit power.

• Adjust motor plate so belts can be installed without stretching over the grooves of the pulley. (Forcing the belts can result in uneven belt stretching and a mismatched set of belts.) See Fig. 51.

• Before tensioning the belts, equalize belt slack so that it is on the same side of the belt for all belts. Failure to do so may result in uneven belt stretching

• Tighten belts using the motor plate adjusting bolts.

• Adjust until proper belt tension (1/2-in. [13 mm] deflection with one finger centered between pulleys) is obtained. Be sure to adjust both adjusting bolts the same number of turns. Excessive belt tension shortens belt life and may cause bearing and shaft damage.

• NOTE: Check the tension at least twice during the first day of operation, as there is normally a rapid decrease in tension until the belts have run in. Check tension periodically thereafter and keep it at the recommended tension.

FIG. 52

To install a field-supplied replacement pulley:

• Turn off unit power

• Loosen belts using motor adjusting bolts until belts can be removed without stretching them over the grooves of the pulley.

• Remove belts.

• Loosen setscrews on motor pulley.

• Slide pulley off motor shaft. Make sure setscrews on new pulley are loose

• Slide new pulley onto fan shaft and align it with the fan pulley as described in Pulley Alignment section above.

• Tighten setscrews.

• Install belts and tension properly as described in Pulley Alignment section above.

CONDENSER FAN ADJUSTMENT (METAL FANS)

• Turn off unit power.

• Remove fan guard and loosen fan hub setscrew.

• See Fig. 53 and adjust fan height using a straight edge laid across the fan deck.

• Tighten setscrew to 12.5 to 13.75 ft-lb and replace rubber hubcap to prevent hub from rusting to the motor shaft. Fill hub recess with Permagum if hub has no rubber hubcap.

• Replace fan guard.

All transducers have been factory calibrated and should not re- quire field adjustment. If field adjustment is necessary, follow the instructions below.

• Shut the unit power off.

• Take the wiring and pressure tubing off the transducer. Take the transducer out of the unit.

• Connect a 24-vdc power supply to transducer terminals EXC(+) and COM(–). See Fig. 55

• Using a digital multimeter measure the current between terminals EXC(+) and OUT.

• With both pressure ports open to atmosphere adjust the Zero (Z) screw potentiometer on the transducer and read the multimeter until the desired current output at 0 in. wg pressure is obtained (see Fig. 55).

• Reinstall the transducer in the unit.

• Restore power to the unit.

The following steps should be taken to clean MCHX condenser coils:

• Remove any foreign objects or debris attached to the core face or trapped within the mounting frame and brackets.

• Put on personal protective equipment, including safety glasses and/or face shield, waterproof clothing, and gloves. It is recommended to use full-coverage clothing.

• Start high-pressure water sprayer and purge any soap or industrial cleaners from sprayer before cleaning condenser coils. Only clean, potable water is authorized for cleaning condenser coils.

• Clean condenser face by spraying the core steadily and uniformly from top to bottom while directing the spray straight toward the core. Do not exceed 30 degree angle. The nozzle must be at least 12 in. from the core face. Reduce pressure and use caution to prevent damage to air centers.

Clean or replace at start of each heating and cooling season or more often if operating conditions require. Refer to Installation Instructions for type and size.

• Remove economizer outdoor-air filters from the hoods by removing the filter retainers.

• Clean filters with steam or hot water and mild detergent.

• Reinstall filters in hoods after cleaning. Never replace cleanable filters with throwaway filters.