6 refrigerant lines and metering devices, 7 condenser coil performance, 8 outdoor unit amp draw – Fieldpiece HG2 - HVAC Guide System Analyzer User Manual

Page 24

WWW.FIELDPIECE.COM WWW.FIELDPIECE.COM WWW.FIELDPIECE.COM WWW.FIELDPIECE.COM WWW.FIELDPIECE.COM WWW.FIIELDPIECE.COM WWW.FIELDPIECE.COM WWW.FIELDPIECE.COM WWW.FIELDPIECE.COM WWW.FIELDPIECE.COM WWW.FIELDPIECE.CO

5.6 Refrigerant Lines and Metering Devices

Research has shown that refrigerant line restric-

tions, incorrect orifi 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 fi lter driers) the charge measurements
will provide contradictory information and getting
proper performance will not be possible. Similarly if the
orifi ce of the metering device is too small or partially
blocked by foreign material in the refrigerant (such as
chips and fl akes from improper brazing technique) the
unit will not perform to specifi cations.

If a fi xed orifi 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 suff 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. Th

erefore it must be well insulated from surround-

ing air. Th

e TXV is designed to maintain a constant su-

perheat.

5.601 Possible oversized metering orifi ce,

consult manufacturer’s specifi cations:

metering orifi ce is suspected of letting too much
refrigerant through. Check that the orifi ce is sized
properly. Find the metering device part number and
obtain the orifi ce size from the manufacturer or dis-
tributor and verify the size is appropriate for the air
conditioner.

5.602 Probable oversized metering orifi ce,

consult manufacturer’s specifi cations:

metering orifi ce lets too much refrigerant through.
Check that the orifi ce is sized properly. Find the
metering device part number and obtain the orifi 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-off 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 diff erence
between the liquid line at the compressor and at the
metering device.

5.7 Condenser Coil Performance

5.701 Condenser airfl ow OK:

e condenser air-

fl 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. Th

ese measure-

ments give indications of the performance of the
air conditioner including diagnoses of compressor
problems, low capacity, and low condenser airfl ow.

5.703 Low condenser airfl ow, clean condens-

er, check condenser fan motor bearings:

ere is insuffi

cient airfl ow going across the con-

denser for the needed heat transfer. Check that the
condenser coils and fi 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.