Carrier 38AQ Specifications download pdf (Page 19)

8. Backseat (open) compressor vapor and discharge valves.

Now close valves one turn to _dlowrefiigerant pressure to

reach test gages.

Preliminary Charge

The 38ARQ008 and 38ARQ012 units contain a 9 lb

(4.1 kg) charge of refrigerant. Add remainder of prelimi-

nary charge and allow pressure to equalize before starting

compressoc Failure to do so WILL cause the compressor

to oveltleat in a few minutes, possibly causing permanent

compressor &_mage. The amount of refrigerant added

must be at least 80% of the operating charge listed in

the Physical Data table (Tables 1A-1D).

Before starting the unit, charge liquid refrigerant into the

high side of the system through the liquid service valve. Allow

high and low side pressures to equalize before stm-ting com-

pressol: If pressures do not equalize readily, charge vapor on

low side of system to assure charge in the evapomtol: Refer to

GTAC II, Module 5, Charging, Recovery. Recycling, and Rec-

lamation for liquid charging procedures.

Liquid Line Solenoid -- To minimize refrigerant migra-

tion to the compressor during the heat pump OFF cycle, the

38AQ,ARQ unit must have a bi-flow liquid line solenoid v;dve

(field supplied). The valve opens when the compressor is ener-

gized, and closes when the compressor is deenergized. This

reduces compressor flooded st_u-ts,thus significantly increasing

compressor life.

Accumulator -- qn_e unit accumulator controls the rate of

liquid ret]igemnt to the compressor during heat pump operation.

The 38AQS accumulator features a unique method for

returning oil to the compressor The oil return mechanism is

external to the accumulatol: The mixture of oil and refrigerant

is metered to the compressor by a brass orifice which is remov-

able and cleanable. The oil return mechanism also contains a

solenoid valve that opens when the compressor is ON and

closes when the compressor is OFF. This keeps the liquid

refrigerant stored in the accumulator from di'aining to the

compressor during the heat pump OFF cycle, which further

protects the compressor against flooded starts.

START-UP

Compressor crankcase heater must be on for 24 hom:s

before st_ul-up. After the heater has been on for 24 hours,

the unit can be started.

Prior to starting compressol: a preliminary ch_uge of refrig-

erant must be added to avoid possible compressor dmnage.

Compressor Rotation (38AQ,ARQ Units) -- On

3-phase units with scroll compressors, it is important to be cer-

tain compressor is rotating in the proper direction. To determine

whether or not compressor is rotating in the proper direction:

1. Connect service gages to suction and discharge pressure

fittings.

2. Energize the compressol:

3. The vapor pressure should &up and the discharge pres-

sure should rise, as is normal on any start-up.

If the vapor pressure does not drop and the discharge

pressure does not rise to normal levels:

1. Note that the condenser fan is probably also rotating in

the wrong direction.

2. Turn off power to the unit, tag disconnect.

3. Reverse any two of the unit power leads.

4. Reapply power to the compressol: verily correct pressures.

The vapor and dischtuge pressure levels should now move

to their norln¢fl start-up levels.

Compressor Overload -- This overload interrupts

power to the compressor when either the current or internal

motor winding temperature becomes excessive, and automati-

cally resets when the intern;d temperature drops to a safe level.

This overload usually resets within 60 minutes (or longer). If

the intermfl overload is suspected of being open, disconnect the

electrical power to the unit and check the circuit through the

overload with an ohmmeter or continuity testel:

Advanced Scroll Temperature Protection

(ASTP) -- Advanced Scroll Temperature Protection

(ASTP) is a form of internal discharge temperature protection

that unloads the scroll compressor when the internal tempera-

ture reaches approximately 300 IF.At this temperatme, an inter-

nal bi-metal disk valve opens and causes the scroll elements to

sepm'ate, which stops compression. Suction and discharge pres-

sures balance while the motor continues to run. The longer the

compressor runs unloaded, the longer it must cool befole the

bi-metal disk resets. See Fig. 17.

To manually reset ASTP. the complessor should be stopped

and allowed to cool. If the compressor is not stopped, the motor

will mn until the motor protector trips, which occurs up to

90 minutes latel: Advanced Scroll Temperatme Protection will

reset automatically before the motor protector resets, which

may take up to 2 hours. A label located above the terlninal box

identities Copeland Scroll compressor models (ZR94, 108 and

125) that contain this technology. See Fig. 18.

0 10 20 30 40 50 60 70 80 90

Compressor Unloaded Run Time (Minutes)

*Times are approximate. Various factors, including high humidity,

high ambient temperature, and the presence of a sound blanket

will increase cool-down times.

Fig. 17- Recommended Minimum Cool-Down

Time After Compressor is Stopped*

Fig. 18 -- Advanced Scroll Temperature

Protection Label

1 2 ... 14 15 16 17 18 19 20 21 22 23 24 ... 31 32

Comments to this Manuals

No comments

Carrier 38AQ Specifications Page 19

Comments to this Manuals

Related products and manuals for Heat pumps Carrier 38AQ