testing residential a/c's in cold outside temperature or in rain 1

[slong1]

What is the proper way to test residential air-conditoners for proper charge in cold outdoor air temperatures below 65 degrees. Also can you test for proper charge in the rain.

 

[Yorkman]

One method if it's a TXE metering device, is to reduce the condenser air flow to raise the head pressure, usually I try to achieve a stable head pressure that corresponds to 80 - 85 degrees, with a clear site glass charge to about 8 - 12 degrees sub-cooling.
With a cap tube it gets a little more challenging, and I would consult the charging chart on the unit or call the manufacturer. With a cap. tube remember that you are charging to superheat and the higher the head pressure (or ambient air) the lower the superheat. Using either method I would still make a return check in warmer weather to verity I'm not under or over charged. Rain generally won't affect the charging too much. It depends on how wet the coil is getting, since the heat transfer is designed to be sensible a wet coil would actually increase the capacity of the condenser for the given ambient dry bulb temperature. It could be possible to under charge a system in a heavey rain storm, and find you are a bit short on a hot dry day.

I'm not a real engineer, but I play one on T.V.
A.J. Gest, York Int.

 

[slong1]

Thank you for your info. I work for a HVAC company and do a lot of a/c tuneups in the spring. With the cold weather I do not feel comfortable saying that the a/c is properly charged espicially in cap tube systems. I do not like recieving call backs for any of my jobs.