Fieldpiece HG2 - HVAC Guide System Analyzer Manuel d'utilisateur télécharger pdf (Page 12)

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3.1 Subcooling

Subcooling is the temperature decrease below the

boiling point (same as the condensing point) in the con-

denser. Too high, and refrigerant condenses too early in

the condenser and ‘wastes’ most of the capacity of the

condenser. Too low, and a mixture of gas and liquid can

be delivered to the expansion valve, reducing e ciency.

Subcooling is the best way to obtain proper refriger-

ant charge for a TXV/EXV system.

If the air conditioner is in good working order and

the air ow is adjusted properly, comparing the actual

and target subcooling will tell you if refrigerant needs

to be added or recovered (ensure the pressure never ex-

ceeds the manufacturer's maximum overload pressure

guidelines).

In a properly working TXV/EXV system, the super-

heat is held constant. Ensure the TXV/EXV bulb is in-

stalled properly, there is proper refrigerant to obtain tar-

get subcooling, and there are no liquid line restrictions.

Adjust refrigerant charge so that the actual subcooling is

within ±3°F of target subcooling.

Figure 11. Using the ASX14 Superheat/Subcooling Head to gather liquid line

temperature and pressure for the HVAC Guide

tester Subcooling Test.

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Fieldpiece HG2 - HVAC Guide System Analyzer Manuel d'utilisateur Page 12