Carrier 48MA/50ME016-040 Forced-Draft Blower 48MA, Optional Economizer Ð See Fig, Pulley Removal

PULLEY REMOVAL

1.Shut off unit power.

2.Loosen fan motor mounting plate and remove belt.

3.Loosen pulley setscrew.

4.Slide pulley off shaft.

Reverse steps 1-4 to install new pulley.

PULLEY ALIGNMENT Ð Loosen fan pulley setscrews and slide fan pulley along fan shaft for parallel alignment. Make angular alignment by loosening motor from mounting plate.

BELT TENSION ADJUSTMENT Ð Loosen fan motor pivot bolts. Pull back motor mounting plate to proper belt tension (approximately 3¤4-in. de¯ection with one ®nger) and tighten motor pivot bolts.

LUBRICATION Ð Evaporator-fan shaft and motor bear- ings require annual lubrication after 3 to 5 years of continu- ous operation as follows:

Fan Shaft Bearings Ð Automotive-type grease ®ttings are factory supplied. Apply a medium-duty, lithium-based grease to ®ttings while rotating shaft.

Fan Motor Bearings Ð Remove plugs and install automotive- type grease ®ttings. Use a suitable motor bearing grease per motor manufacturer's recommendations.

Forced-Draft Blower (48MA)

LUBRICATION Ð Add 2 or 3 drops of a good grade of no. 20 SAE (Society of Automotive Engineers) motor oil at each oil cup on the motor once a year.

AIR SHUTTER ADJUSTMENT Ð The air shutter is held in position on the blower inlet by a wing nut. Loosen wing nut and reposition shutter until correct pressure is achieved. Combustion chamber air pressure is to be measured through drain connection below heat exchangers. Correct pressures are 0.10 ± 0.01 in. wg for units 48MA016,024,034, and 040;

0.14± 0.01 for units 48MA028 and 030. Figure 39 shows correct shutter position. Note pivot hole location.

Zone Module Transformers Ð When replacing these transformers, be sure to connect wires on correct terminals to maintain correct polarity. See base unit label diagram on the unit for connections.

Optional Economizer Ð See Fig. 40.

THERMOSTAT SETTINGS Ð Set economizer outdoor air thermostat (ECT) at a temperature which will provide cool- ing with outdoor air only. This setting, when achieved, will lock out the compressor(s). A 45 F setting is suggested.

Set mixed-air thermostat (MAT) as desired to provide mixed air of the correct temperature. This setting cannot be lower than the ECT setting. A 58 F setting is suggested.

48MA016 AND 024 48MA028-040

Fig. 39 Ð Forced-Draft Blower

Shutter Position

DAMPER POSITION Ð When outdoor-air damper is fully open, the return-air damper will be fully closed and vice versa.

OPERATION

Heating or Compressor Cooling Ð Dampers will assume the ventilation position indicated by the ventilation control knob. If a remote control center is used, DAY/NIGHT switch must be at the DAY position.

If terminals in unit control box labeled SHORT TO CLOSE DAMPERS are shorted or if DAY/NIGHT switch is set at NIGHT position, outdoor-air damper will close.

Intermediate Season (Free Cooling Using Optional Econo- mizer) Ð If outdoor-air temperature drops below econo- mizer outdoor-air thermostat (ECT) setting, the compressor(s) will remain off. The dampers will modulate to maintain the mixed-air thermostat (MAT) setting. If the outdoor air tem- perature rises above the ECT setting, the unit will operate as described in Heating or Compressor Cooling section above.

Optional Exhaust Damper Ð See Fig. 34 and 35. When unit is on economizer cycle (free cooling) and an ex- haust damper is part of the unit, the exhaust relay is ener- gized. The fan motor controls the Motormaster head pres- sure control and the fan cycling pressure switches are bypassed so that condenser fans operate at full speed as follows:

·Fan no. 1 and 2 on units 48MA/50ME016-030

·Fan no. 2 and 3 on units 48MA/50ME034,040

When the return air damper is 25% closed, the exhaust damper begins to open. The condenser fans pull indoor re- turn air through the open exhaust damper and discharge it to the outdoors.

Replacement Parts Ð A complete list of replacement parts may be obtained from any Carrier distributor upon request.

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