Bryant 551A Start-Up, Unit Preparation, II. Compressor Mounting, III. Refrigerant Service Ports

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. COMPRESSOR MOUNTING

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

III. REFRIGERANT SERVICE PORTS

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

IV. 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.

NOTE: When compressors are rotating in the wrong direc- tion, the unit will have increased noise levels and will not provide heating and cooling.

After a few minutes of reverse operation, the scroll compres- sor internal overload protection will open, which will acti- vate the unit’s lockout and requires a manual reset. Reset is accomplished by turning the thermostat on and off.

V. INTERNAL WIRING

Check all electrical connections in unit control boxes; tighten as required.

VI. CRANKCASE HEATERS

Heaters are energized as long as there is power to unit and compressor is not operating.

IMPORTANT: Unit power must be on for 24 hours prior to start-up. Otherwise, damage to compressor may result.

VII. EVAPORATOR FAN

Fan belt and variable pulleys are factory installed. Remove tape from the fan pulley. See Table 8 for Air Quantity Limits. See Tables 9-12 for Fan Performance data. Be sure that fans rotate in the proper direction. See Tables 13 and 14 for Static Pressure information for accessories and options. See Table 15 for fan rpm at various fan motor pulley settings. See Table 16 for Evaporator-Fan Motor Specifications. To alter fan performance, see Evaporator-Fan Performance Adjustment section, page 26.

Table 8 — Air Quantity Limits

UNIT	MINIMUM CFM	MAXIMUM CFM
551A
155	3600	6,000
180	4500	7,500
240	6000	10,000

VIII. CONDENSER FANS AND MOTORS

Condenser fans and motors are factory set. Refer to Condenser-Fan Adjustment section (page 28) as required. Be sure that fans rotate in the correct direction.

IX. RETURN-AIR FILTERS

Check that correct filters are installed in filter tracks. See Table 1. Do not operate unit without return-air filters.

X. OUTDOOR-AIR INLET SCREENS

Outdoor-air inlet screens must be in place before operating unit.

XI. ACCESSORY ECONOMI$ER ADJUSTMENT

Remove filter access panel. Check that outdoor-air damper blades are closed and return-air damper blades are open.

EconoMi$er operation and adjustment is described in Base Unit Operation and EconoMi$er Adjustment sections (this page and page 28), respectively.

XII. BASE UNIT OPERATION

A. Cooling, Units Without EconoMi$er

When thermostat calls for cooling, terminals G and Y1 are energized. The indoor (evaporator) fan contactor (IFC), and compressor contactor no. 1 (C1) are energized and evaporator-fan motor, compressor no. 1 and condenser fans start. The condenser-fan motors run continuously while unit is cooling. If the thermostat calls for a second stage of cooling by energizing Y2, compressor contactor no. 2 (C2) is ener- gized and compressor no. 2 starts.

B. Heating, Units Without EconoMi$er (If Accessory or Optional Heater is Installed)

Upon a call for heating through terminal W1, IFC and heater contactor no. 1 (HC1) are energized. On units equipped for 2 stages of heat, when additional heat is needed, HC2 is energized through W2.

C. Cooling Units With EconoMi$er

When the OAT is above the ECON SP set point and the room thermostat calls for Stage 1 cooling (R to G + Y1), the indoor- fan motors (IFM) is energized and the EconoMi$er damper modulates to minimum position. The compressor contactor and OFC are energized to start the compressor and outdoor- fan motor (OFM). After the thermostat is satisfied, the damper modulates to the fully closed position when the IFM is deenergized.

When the OAT is below the ECON SP setting and the room thermostat calls for Stage 1 cooling (R to G + Y1), the EconoMi$er modulates to the minimum position when the IFM is energized. The EconoMi$er provides Stage 1 of cool- ing by modulating the return and outdoor air dampers to maintain a 55 F supply air set point. If the supply-air tem- perature (SAT) is greater than 57 F, the EconoMi$er modu- lates open, allowing a greater amount of outdoor air to enter the unit. If the SAT drops below 53 F, the outdoor air damper modulates closed to reduce the amount of outdoor air. When the SAT is between 53 and 57 F, the EconoMi$er maintains its position.

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