Rheem A/C confusion

[joeblo]

I looked at a Rheem A/C earlier today and I am a bit confused. Model 13aja24a01, 2 ton, R-22, 5 years old, 2 ton "N" cased coil with txv on Rheem 60,000 btu furnace. Outdoor temp.- 76*, indoor temp.- 68*, indoor wet bulb - 58*, head pressure - 180psi, suction - 74psi, coil temp - 44*, subcooling - 10*, superheat - 9*, return air temp - 68*, supply temp - 49*, temp drop - 19*. With a 68* return temp i would expect a lower suction pressure and coil temp around 30*, and on a 76* day a higher head pressure. Looking at that info it would appear that the compressor is not operating at full capacity, but if that were the case how do I get a 19* temp. drop? Air flow, duct work and filter are all good. What do you guys think? Should this compressor be replaced or am I missing something? I hate to let it go because the compressor warranty runs out in a week.

[ga-hvac-tech]

Are you sure you have 800 CFM's going across the coil?

[addamsmasher]

Our rheem rep has told us to charge in cooling to 8 deg. Sub cooling.

Ps why does the compressor need replacing?

[joeblo]

Did not measure air flow at all registers but with hotwire its around 900. If the air flow was to high I would expect a much lower tempature drop, and if air flow to low I would expect a much lower suction pressure. I also checked to make sure there was no air flow around coil, its tight.

[joeblo]

Took some refrigerant out to see what would happen, had subcooling down to 3-4 degrees, very little if any change in condition. Put it back in.

[BaldLoonie]

Looks pretty good to me. 13 SEER units run a lower head and higher suction than low SEER units.

[jpsmith1cm]

Run a total capacity calculation.

1.08 x cfm x delta DB
.68 x cfm x delta W (grains of moisture)

This will tell you with 100% certainty if you're working properly or not.


Myself, I'd be pretty happy with those numbers.

[beenthere]

Numbers looked good. Working like it should, put the gas back in.

[jpbhvac]

I would suggest leaving this system alone. Remember, every situation calls for its own individual analysis. Focus on this diagnosis and don't be bogged down by what you think it should be.


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[mustanger361]

It is important to me -- this is a priority for me -- in every charging situation, to determine if liquid is returning to the compressor. Many times, that over-rides all the other calculations. At the very least, it strongly influences my decisions about the general condition of the system.

[mustanger361]

I would suggest leaving this system alone. Remember, every situation calls for its own individual analysis. Focus on this diagnosis and don't be bogged down by what you think it should be.


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Chances are, you are using the right approach. I have rarely seen the numbers all line up perfectly by the book. And that's only with a fresh new system.

[joeblo]

Thanx guys for all your help and input. I will be leaving it as is. I thought all was well but had an odd feeling about those pressures.