WeatherMaster® Single-Packaged Rooftop Units 48P: Periodical Maintenance (bi-monthly)

COMBUSTION-AIR BLOWERS (48P ONLY)

Clean periodically to assure proper airflow and heating efficiency. Inspect blower wheel every fall and periodically during heating season. For the first heating season, inspect blower wheel bi-monthly to determine proper cleaning frequency.

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 (Fig. 49).
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.

SUPPLY FAN AND POWER EXHAUST MOTOR PLATE

Adjust using a 15/16-in. wrench on the adjusting bolts:

Loosen holddown bolts. (See Fig. 51.)
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.
Re-tighten 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.

BELT INSTALLATION AND TENSIONING:

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.)
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.

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.

With the correct belt tension, belts may slip and squeal momentarily on start-up. This slippage is normal and disappears after wheel reaches operating speed. Excessive belt tension shortens belt life and may cause bearing and shaft damage.

PULLEY ALIGNMENT

For proper belt life, the motor and fan pulleys must be properly aligned. To check, first turn off unit power. Place a straightedge against the motor and fan pulleys. See Fig. 52. If the pulleys are properly aligned, the straightedge should be parallel to the belts.

If they are not parallel, check that the motor shaft and fan shaft are parallel. If they are not, adjust the motor plate adjusting bolts until they are.

After verifying that the shafts are parallel:

Loosen the setscrews on the motor pulley.
Move pulley on the shaft until the pulleys are parallel.
To move the sheave on the shaft, loosen the belts.
If necessary, blower sheave can also be moved on the shaft.

INSTALLING REPLACEMENT MOTOR PULLEY (SUPPLY FAN ONLY)

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.
Tighten setscrews.
Install belts and tension properly as described in Pulley Alignment section

CONDENSER FAN ADJUSTMENT (ALL UNITS EXCEPT SIZE 035)

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.

COMBUSTION-AIR BLOWERS (48P ONLY)

Clean periodically to assure proper airflow and heating efficiency. Inspect blower wheel every fall and periodically during heating season. For the first heating season, inspect blower wheel bi-monthly to determine proper cleaning frequency.

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 (Fig. 49).

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.

SUPPLY FAN AND POWER EXHAUST MOTOR PLATE

Adjust using a 15/16-in. wrench on the adjusting bolts:

Loosen holddown bolts. (See Fig. 51.)

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.

Re-tighten 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.

BELT INSTALLATION AND TENSIONING:

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.)

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.

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.

With the correct belt tension, belts may slip and squeal momentarily on start-up. This slippage is normal and disappears after wheel reaches operating speed. Excessive belt tension shortens belt life and may cause bearing and shaft damage.

PULLEY ALIGNMENT

For proper belt life, the motor and fan pulleys must be properly aligned. To check, first turn off unit power. Place a straightedge against the motor and fan pulleys. See Fig. 52. If the pulleys are properly aligned, the straightedge should be parallel to the belts.

If they are not parallel, check that the motor shaft and fan shaft are parallel. If they are not, adjust the motor plate adjusting bolts until they are.

After verifying that the shafts are parallel:

Loosen the setscrews on the motor pulley.

Move pulley on the shaft until the pulleys are parallel.

To move the sheave on the shaft, loosen the belts.

If necessary, blower sheave can also be moved on the shaft.

INSTALLING REPLACEMENT MOTOR PULLEY (SUPPLY FAN ONLY)

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.

Tighten setscrews.

Install belts and tension properly as described in Pulley Alignment section

CONDENSER FAN ADJUSTMENT (ALL UNITS EXCEPT SIZE 035)

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.