Fieldpiece HG2 - HVAC Guide System Analyzer Manual de usuario descargar pdf (Pagina 24)

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5.6 Refrigerant Lines and Metering Devices

Research has shown that refrigerant line restric-

tions, incorrect ori ce sizes, and TXVs improperly in-

stalled are far more common than originally thought.

All of these problems can lead to premature compressor

failure.

If there are restrictions in the refrigerant lines

(pinches, dirty  lter driers) the charge measurements

will provide contradictory information and getting

proper performance will not be possible. Similarly if the

ori ce of the metering device is too small or partially

blocked by foreign material in the refrigerant (such as

chips and  akes from improper brazing technique) the

unit will not perform to speci cations.

If a  xed ori ce is too large (not matched to the in-

side coil), the refrigerant will not meter properly, con-

tradictory measurements will be obtained, and perfor-

mance will su er.

A thermostatic expansion valve (TXV) only works

when the sensing bulb is in solid contact with the suc-

tion line and only senses the temperature of the suction

line.  erefore it must be well insulated from surround-

ing air.  e TXV is designed to maintain a constant su-

perheat.

5.601 Possible oversized metering ori ce,

consult manufacturer’s speci cations:  e

metering ori ce is suspected of letting too much

refrigerant through. Check that the ori ce is sized

properly. Find the metering device part number and

obtain the ori ce size from the manufacturer or dis-

tributor and verify the size is appropriate for the air

conditioner.

5.602 Probable oversized metering ori ce,

consult manufacturer’s speci cations:  e

metering ori ce lets too much refrigerant through.

Check that the ori ce is sized properly. Find the

metering device part number and obtain the ori ce

size from the manufacturer or distributor and verify

the size is appropriate for the air conditioner.

5.603 Check TXV to ensure proper function-

ing:  is TXV is not maintaining proper superheat.

Check that the TXV bulb is adjusted properly and

in continuous contact with the suction line and well

insulated from the surrounding air.

5.604 Probable liquid line restriction, check

liquid line: Make sure the service shut-o valves

are open. Check the liquid line for kinks, tight

bends or sections that may have been stepped on

or crushed. Check for a large temperature di erence

between the liquid line at the compressor and at the

metering device.

5.7 Condenser Coil Performance

5.701 Condenser air ow OK:  e condenser air-

 ow and capacity indications are OK.

5.702 Condenser approach unknown, check

condenser approach: Liquid line temperature

and liquid line pressure measurements need to be

taken at the condenser approach.  ese measure-

ments give indications of the performance of the

air conditioner including diagnoses of compressor

problems, low capacity, and low condenser air ow.

5.703 Low condenser air ow, clean condens-

er, check condenser fan motor bearings:

 ere is insu cient air ow going across the con-

denser for the needed heat transfer. Check that the

condenser coils and  ns are clean, aligned and free

of nearby obstructions. Check the fan motor bear-

ings to ensure that the fan is rotating freely.

5.8 Outdoor Unit Amp Draw

 e outdoor unit amp draw gives indications of the

health of the compressor as well as overcharge and con-

denser coil performance.

5.801 Outdoor amp draw OK:  e outdoor unit

is running at the proper amperage for the current

conditions.

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