Fieldpiece HG2 - HVAC Guide System Analyzer Uživatelský manuál stáhnout pdf (Strana 22)

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5.407 High air ow, possibly reduce air ow:  e

indoor coil air ow was directly measured using the

TrueFlow grid and is higher than expected. Consider

reducing the air ow particularly if the unit is in a

damp climate. In heat pumps high air ow causes un-

comfortably low delivery temperatures.

5.408 Possible plenum temperature measure-

ment error, retake plenum temperatures:

 e reported wet and dry bulb temperature readings

from the return and supply plenums are unlikely. Re-

take the measurements in the INPUT FORM. See Re-

turn DB and Return WB sections for detailed instruc-

tions on how to take these measurements properly.

5.5 Refrigerant Charge

Incorrect refrigerant charge is the most common

problem with air conditioners and heat pumps.  ere are

widespread poor practices and misinformation regarding

refrigerant levels.

 e primary method speci ed by major manufactur-

ers for non-TXV ( xed metering device) systems is su-

perheat.  e superheat needs to be matched to the target

superheat, which changes with indoor and outdoor condi-

tions.  e optimum refrigerant charge as indicated by su-

perheat is a ected by the air ow across both coils. Repair

any air ow problems before setting the  nal refrigerant

charge.

 e primary method for TXV or EXV systems is

subcooling.  e subcooling needs to be matched to the

target subcooling.  e target subcooling is usually on the

manufacturer's ID plate along with the model and serial

numbers.

For heat pumps, it is best to set the refrigerant levels

in the summer in the cooling mode.  e HG2 can also

check the capacity of heat pumps in the winter as an indi-

cator of correct refrigerant charge.

5.501 Charge OK: Refrigerant charge was tested us-

ing the appropriate method and it is OK.

5.502 Possible OK charge:  e primary indicator of

refrigerant charge (subcooling for TXV/EXV or su-

perheat for non-TXV) indicates the refrigerant level

was OK. However, a secondary indicator reduces the

con dence in that diagnosis. Check out any other po-

tential problems indicated.

5.503 Charge unknown, check charge:  e mea-

surements are insu cient to diagnose the refrigerant

charge. For best results, measure both the suction line

temperature and pressure as well as the liquid line

temperature and pressure and press the OUTPUT

button again.

5.504 Possible undercharge, possibly add re-

frigerant: If no other conditions are triggered, con-

sider adding refrigerant to correct.  ere is possibly

insu cient refrigerant in the system.  e amount of

refrigerant necessary to add will vary based on the

size of the system and the di erence between Target

and Actual superheat/subcooling.

5.505 Probable undercharge, add refrigerant:

It is very likely that there is insu cient refrigerant in

the system. Add refrigerant to bring the superheat or

subcooling to within the target.

5.506 Undercharged, add refrigerant until ac-

tual superheat reaches target superheat:  is

non-TXV system is low on refrigerant. Add refriger-

ant until the superheat is within the proper range

(usually ±5°F) of the target superheat.  e closer the

superheat is to the target, the better.

5.507 Undercharged, add refrigerant to obtain

6°F of superheat:  is non-TXV system is low on

refrigerant. Since the test conditions are hot outside,

dry inside, or both, the exact target superheat cannot

be determined. Because the superheat is greater than

6°F the unit is undercharged. Add refrigerant until the

superheat is 6°F.

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