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Old 01-05-2011, 07:58 AM   #1
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Goodman heatpump subcooling too high


I recently check my 2 1/2 ton R410a heatpump for pressures and subcooling in heat mode. All pressures at outside ambient temp (47 degrees) were within extended performance data ranges, however the subcooling was 27 degrees. This is well higher than normal recommended levels for this application. My question is: Should I remove refrigerant until I reach the recommended subcooling range or should I wait until the outside temp gets up to about 70 degrees and check superheat & subcooling in cooling mode to adjusted the charge level?

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Old 01-05-2011, 06:56 PM   #2
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Goodman heatpump subcooling too high


you can't check in heating properly. leave alone until warm outside and check in cooling. or, and I do not recommend this, remove all refrigerant vacuum system and weigh in charge and it will probably still be off

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Old 01-05-2011, 08:14 PM   #3
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Goodman heatpump subcooling too high


Agreed. Since your performance matches the data then the charge is likely correct. Bet the subcool is perfect when it warms up an checked in cooling.
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Old 01-06-2011, 04:55 AM   #4
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Goodman heatpump subcooling too high


Where did you get your heating SC values/specs from.

They don't run the same SC in heating as in cooling mode.
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Old 01-06-2011, 11:27 AM   #5
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Goodman heatpump subcooling too high


Great Question "beenthere" .
When I posted this, the subcoolling value I used was a general range of 12 to 15 degrees. I got this from an HVAC article. I have since found in the technical info for my unit the recommend service manuel which contains a chart listing the servicing requirements for liquid line temp at a given liquid pressure and SC temp. The SC range on the chart only goes from 8 to 18 degrees. There is a two degree drop in liquid line temp at a given pressure across the SC temp range. If I continue the chart SC range out to 27 with a two degree drop in liquid line temp for each two degrees increase in SC I find that the liquid line temp is what I measured when I tested the unit. This indicates the unit is properly charged. The moral of the story is: Find the correct documentation before you start troubleshooting and "Don't fix it if it ain't broke!"
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