Bryant operation manual B. Motormaster III Control Installation 581A240, Locations, Start-Up

Sensor Assembly — Install the sensor assembly in the loca- tion shown in Fig. 26.

Motor Mount — To ensure proper fan height, replace the existing motor mount with the new motor mount provided with accessory.

Transformer (460-v Units Only) — On 460 volt units, a trans- former is required. The transformer is provided with the accessory and must be field-installed.

Motormaster® I Control — Recommended mounting location is on the inside of the panel to the left of the control box. The control should be mounted on the inside of the panel, verti- cally, with leads protruding from bottom of extrusion.

B. Motormaster III Control Installation (581A240)

Install Field-Fabricated Wind Baffles

Wind baffles must be field-fabricated for all units to ensure proper cooling cycle operation at low ambient temperatures. See Fig. 25 for baffle details. Use 20-gage, galvanized sheet metal, or similar corrosion-resistant metal for baffles. Use field-supplied screws to attach baffles to unit. Screws should be 1/4-in. diameter and 5/8-in. long. Drill required screw holes for mounting baffles.

CAUTION: To avoid damage to the refrigerant coils and electrical components, use recommended screw sizes only. Use care when drilling holes.

MOTORMASTER

SENSOR

LOCATION

HAIRPIN END

NOTES:

1.All sensors are located on the eighth hairpin up from the bottom.

2.Field installed tubing insulation is required to be installed over the TXV (thermostatic expansion valve) bulb and capillary tube for proper operation at low ambients. Tubing insulation is only required on the portion of suction line located between indoor and outdoor section.

Fig. 26 — Motormaster I and Motormaster III Sensor

Locations

Replace Outdoor Motor

Replace outdoor-fan motor no. 1 with motor included in accessory kit. Existing motor is not Motormaster III compatible.

Install Motormaster III Controls

Only one Motormaster III control is required per unit.

Sensor — Install the sensor for thermistor input control in the location shown in Fig. 26. Connect sensor leads to the purple and grey control signal leads on the Motormaster III control.

Signal Selection Switch — Remove the cover of the Motor- master III control. Set the switch to accept the thermistor sensor input signal. Set the frequency to match the unit power supply (60 Hz).

Motormaster III Control — Recommended mounting location is beneath the control box, mounted to the partition that sep- arates the control box section from the indoor section.

NOTE: If unit power is supplied through the roof curb and basepan of the unit, mount the Motormaster III control on the corner post adjacent to the conduit running from the basepan to the bottom of the control box.

START-UP

Use the following information and Start-Up Checklist on page CL-1 to check out unit PRIOR to start-up.

I. UNIT PREPARATION

Check that unit has been installed in accordance with these installation instructions and all applicable codes.

II. SERVICE VALVES

Ensure that the liquid line service valve is open. Damage to the compressor could result if it is left closed.

III. COMPRESSOR MOUNTING

Compressors are internally spring mounted. Do not loosen or remove compressor holddown bolts.

IV. REFRIGERANT SERVICE PORTS

Each refrigerant system has a total of 3 Schrader-type ser- vice gage ports. One port is located on the suction line, one on the compressor discharge line, and one on the liquid line. In addition Schrader-type valves are located underneath the low-pressure switches. Be sure that caps on the ports are tight.

V. COMPRESSOR ROTATION

It is important to be certain the compressors are rotating in the proper direction. To determine whether or not compres- sors are rotating in the proper direction:

1.Connect service gages to suction and discharge pres- sure fittings.

2.Energize the compressor.

3.The suction pressure should drop and the discharge pressure should rise, as is normal on any start-up.

If the suction pressure does not drop and the discharge pres- sure does not rise to normal levels:

1.Note that the evaporator fan is probably also rotating in the wrong direction.

2.Turn off power to the unit.

3.Reverse any two of the incoming power leads.

4.Turn on power to the compressor.

The suction and discharge pressure levels should now move to their normal start-up levels.

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