freon charge in a Dometic

garysol wrote:
Hi everyone. Is there anyway to verify low freon charge in a Dometic 15,000btu without installing a line tap and ambient air temperature is to cold to really check output temperature? Compressor load test maybe?

I don't believe there is any such option as they are all sealed units.

You take a TEMP compensated AMP draw of the compressor. VERY accurate. There is a Compressor AMP draw stated on the AC model label. THAT amp draw is based on 95 degree ambient temp. So, you subtract 1 AMP for every 10 degrees below 95 degrees. ADD 1 AMP for every 10 degrees above 95. Lets say the Rating is 12.2 amps for the compressor. It is 75 degrees outside. Subtract 2 amps. The Compressor after running a minimum of 15 minutes will draw 10.2 amps. IF lower, by more than 1 amp, you have lost part of the charge. IF 80 degrees subtract 1.5 amp, same test. Doug

Thank You Doug! I had never known that. I learned something new today.

dougrainer wrote:
You take a TEMP compensated AMP draw of the compressor. VERY accurate. There is a Compressor AMP draw stated on the AC model label. THAT amp draw is based on 95 degree ambient temp. So, you subtract 1 AMP for every 10 degrees below 95 degrees. ADD 1 AMP for every 10 degrees above 95. Lets say the Rating is 12.2 amps for the compressor. It is 75 degrees outside. Subtract 2 amps. The Compressor after running a minimum of 15 minutes will draw 10.2 amps. IF lower, by more than 1 amp, you have lost part of the charge. IF 80 degrees subtract 1.5 amp, same test. Doug

If you have a low charge, it MUST have a leak. I have never seen a Low charged RV unit in 41 years as an RV tech, that did not have a leak. They only hold about 1 lb of coolant. So any leak will cause a drastic reduction of cooling. Doug

You use the old 4 point thermometer and ammeter to do it
Inlet and outlet temps both inside and out
Humidity
And compressor amperage
And then there should be a book that tells you what you need to know.
The problem is the books are specific to the make and model and I have no clue where to find it. outside temps should be over freezing. help if over 40

I think what you are referring to, is/was for commercial systems, and very likely that no such books are published pertaining to RV units
Can't read what's never been printed

I use info published by a different a/c maker.

https://www.airxcel.com/docs/default-source/coleman-mach/mach-15/evaluating_ac_performance.pdf?sfvrsn=8f50e6b_5

red31 wrote:
I use info published by a different a/c maker.

https://www.airxcel.com/docs/default-source/coleman-mach/mach-15/evaluating_ac_performance.pdf?sfvrsn=8f50e6b_5

The chart is WRONG. If you use RVP's 5 degrees instead of the correct 10 degrees, EVERY RVP unit will show BAD. I went thru this with RVP 3 years ago at the last training school. Doug