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13 Subcooling Charging Method

This document discusses charging a thermostatic expansion valve (TXV) system using subcooling. It explains that TXV systems must be charged using subcooling to maintain a positive liquid seal. To determine the proper subcooling, measure the liquid line temperature and pressure, convert the pressure to saturation temperature, and take the difference which will be the operating subcooling. The target subcooling is usually between 7-12°F. Add refrigerant to increase subcooling and recover refrigerant to decrease subcooling.

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200 views7 pages

13 Subcooling Charging Method

This document discusses charging a thermostatic expansion valve (TXV) system using subcooling. It explains that TXV systems must be charged using subcooling to maintain a positive liquid seal. To determine the proper subcooling, measure the liquid line temperature and pressure, convert the pressure to saturation temperature, and take the difference which will be the operating subcooling. The target subcooling is usually between 7-12°F. Add refrigerant to increase subcooling and recover refrigerant to decrease subcooling.

Uploaded by

Kurkuma Plus
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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Subcooling

Charging Method
METERING DEVICES - TXV
Charging Thermostatic Expansion Valve
(TEV) Systems

• The TEV will maintain design superheat under a


variety of conditions
• For this reason, these systems must be CHARGED
using sub-cooling
• Proper sub-cooling will maintain a positive liquid
seal at the TEV entrance
• Determine the required sub-cooling from the IO
or the unit datasheet (usually from about 7°F to
about 12°F
Determine Operating Subcooling
111°F

Liquid Line

Suction Line (Vapor)

Measure Liquid Line Temperature


118 PSIG 417 PSIG

• Measure Liquid Line Pressure


• Convert Pressure to Saturation Temperature
• Subtract SATURATION Temperature from
ACTUAL Temperature
• The Difference is OPERATING Sub-cooling
Checking Subcooling
Sub-cooling = Sat. Liquid Temp. - Liquid Line Temp.
EXAMPLE:
a. Liquid Line Pressure = 417
b. Corresponding Temp. °F. = 120°
c. Thermometer on Liquid line = 111°F.
To obtain the amount of sub-cooling subtract
111°F from 120°F.
The difference is ° sub-cooling.
Sub-cooling should be 9 ºF (+ or - 2°F)
 Add charge to raise subcooling.
 Recover charge to lower subcooling.
Temperature Probe
Test Point Locations

• LIQUID LINE SERVICE VALVE


• (Smaller of the two copper lines)
• INSULATE THE PROBE FOR A MORE
ACCURATE READING

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