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AC help! New coil installed, old compressor - ok?


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Good evening.

Question for the knowledgeable (there seems to be many here):

Evap coil on the house went bad, had new coil/furnace installed.

Higher heat, ac unit will not cool. Evening comes, and ac blows cool. AC guy said compressor is bad, but if compressor is bad, should be all the time right?

Outside units is a RUUD AUFD036JAS, Design pressure H - 300psig, Dsn Press. L is 150psig.

New evap coil is a Rheem RCFA HM3617AC, says 550psi.

Are these systems mismatched, causing my ac not to cool in higher heat conditions?

AC guy tried the parts replacement troubleshoot method, my experience with old cars says ineffective and expensive way to fix.

Any words of wisdom?



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Looking at the model numbers it looks like both are 3 tons (the 36 in the model number means 36,000 BTUs) although I haven't looked these up to be 100% positive.

What temperature is the discharge air in the house during the day and then at night? It's hard to help without knowing exact temperatures. It may get cooler at night but still not be cooling.

In 2010 R-22, the most common refrigerant for air conditioning, will be phased out for new equipment. New air conditioners will be shipped with a different refrigerant. When these are installed to an existing system the evaporator will need to be changed out as well as the copper lines going between the evaporator and the condensing unit. R-22 will still be available for another 10 years after that though. Hopefully the service technician explained this to you before he replaced the evaporator. You can read about it here: http://www.epa.gov/Ozone/title6/phaseou ... seout.html

As stated before I would get a second opinion from another HVAC company.

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There are more factors at work than what you are giving us.

The age of the compressor/condensing unit?

Overall condition; Clean, not clogged up with dog hair,weeds, dirt, no damage? Picture?

It's kind of hard to evaluate something over the internet...

What factors did your HVAC guy tell you made it necessary to replace it?

He should be checking the refrigerant pressure, the amount of current the compressor is drawing versus it's rating, noise and delta T. Probably the most important is the current draw and weather it is holding pressure.

It may be working better at night just cause it is cooler outside at night and there is not as much load on it.

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  • 1 month later...

New Here!

Just ran across this looking for code for new oil furnace install chimney liner, and wanted to give a heads up on this topic.

The coil can be changed out with another manufacturers but you have to make sure they used the correct piston size on the coil. If not then you would have a change in cooling due to the evaporator starving or flooding.

Also before condemning a compressor, make sure a hard start kit was tried!

Back to my issue!

Installing a new oil furnace, does the chimney have to be lined?



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