Carrier 50ZH Instruction Manual download pdf (Page 10)

Step 2—Start-Up Cooling Section and Make Adjustments

Complete the required procedures given in the Pre-Start- Up

section this page before starting the unit. Do not jumper any

safety devices when operating the unit.

Do not operate the compressor in cooling mode when the

outdoor temperature is below 40 F.

Do not rapid-cycle the compressor. Allow 5 minutes between

‘‘on’’ cycles to prevent compressor damage.

CHECKING COOLING CONTROL OPERATION

Start and check the unit for proper cooling control operation as

follows:

1. Place room thermostat SYSTEM switch in OFF position.

Observe that blower motor starts when FAN switch is placed

in ON position and shuts down within 30 seeconds when FAN

switch is placed in AUTO position.

2. Place SYSTEM switch in COOL position and FAN switch in

AUTO position. Set cooling control below room temperature.

Observe that compressor, outdoor fan, and indoor blower

motors start and that reversing valve shifts. Observe that

cooling cycle shuts down when control setting is satisfied.

Reversing valve (RV) remains energized.

3. Place system switch in HEAT position. Observe that compres-

sor, indoor fan and outdoor fan energize (Reversing Valve is

deenergized in heat pump heating mode). Set control above

room temperature. Observe that heating cycle shuts down

when control setting is satisfied.

4. When using an automatic changeover room thermostat, place

both SYSTEM and FAN switches in AUTO. positions.

Observe that unit operates in Cooling mode when temperature

control is set to ‘‘call for cooling’’ (below room temperature),

and unit operates in Heating mode when temperature control

is set to “call for heating” (above room temperature).

COMPRESSOR ROTATION

On all 3–Phase units it is important to be certain compressor is

rotating in the proper direction. To determine whether or not

compressor is rotating in the proper direction:

1. Connect service gauges to suction and discharge pressure

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 pressure

does not rise to normal levels:

1. Turn off power to the unit and tag disconnect.

2. Reverse any two of the unit power leads.

3. Turn on power to the unit.

The suction and discharge pressure levels should now move to

their normal start-up levels.

NOTE: When the compressor is rotation in the wrong direction,

the unit makes an elevated level of noise and does not provide

cooling.

Step 3—Refrigerant Charge

Refrigerant Charge — Amount of refrigerant charge is listed on

unit nameplate and in Table 1. Refer to Carrier Refrigerant Service

Techniques Manual, Refrigerants section. Unit panels must be in

place when unit is operating during charging procedure. Unit must

operate a minimum of 15 minutes before checking charge.

NO CHARGE

Refer to Carrier Refrigerant Service Techniques. Use standard

evacuating techniques. After evacuating system, weigh in the

specified amount of refrigerant (refer to Table 1).

LOW CHARGE COOLING

Using cooling charging chart (see Fig. 18–22),Vary refrigerant

until conditions of the chart are met. Note that charging chart is

different from those normally used. Charts are based on charging

the units to the correct superheat for the various operating

conditions. An accurate pressure gauge and temperature-sensing

device is required. Connect the pressure gauge to the service port

on the suction line. Connect temperature sensing device to the

suction line near the compressor and insulate it so that outdoor

ambient temperature does not affect reading.

Fig. 11—Unit Electrical Connection

C00010

HIGH-VOLTAGE

POWER WIRING

ENTRY HOLE

LOW-VOLTAGE

WIRING ENTRY

HOLE

Fig. 12—Control Box Wiring

C00011

ELECTRIC

HEATER

FUSES

GROUND

LUG

INDOOR

FAN

RELAY

OUTDOOR FAN MOTOR

AND COMPRESSOR

START CAPACITOR

HIGH

VOLTAGE

LEADS

1 ... 9 10 11 ... 24

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Carrier 50ZH Instruction Manual Page 10

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