Greetingsfrom the Plumbing Page,
Here's my problem. Back in 87 I swapped my old pot type oil burner for a air handler and heat strip. This air handler is what the AC company was installing on the condos where I was the plumbing foreman. I used a 2 ton wall banger for the next 20 years to cool in the summer and the air handler to heat in the winter.
Two years ago the wall banger left to go to "wall banger heaven" so I had a installed a Goodman 2 ton 13 Seer compressor unit installed.
Hang in there!! I'm just giving you some background. I'm getting to the problem right now.
From time to time I noticed the air blowing from the handler was room temperature for a while and the went back to blowing cold.
When I called and questioned this I was told that this was normal because the compressor was 13 Seer and the air handler was only 8 seer.
Can this be true? I didn't like that explanation then an d I don't like it now.
What can I do. It's getting worse and it's August in SouthWest Florida. HOT!! I think the compressor's overheating and the breaker's shutting the unit down until it cools down
But what do do I know? I'm just a plumber not a AC tech.
What's it sound like to you guys? What's causing this and how can it be fixed?
Help a old retired plumber stay cool. Thanks, Tom

Try cleaning the outdoor coils... if they are dirty the compressor will overheat and could be tripping on thermal overlaod. Might also want to have the capacitors checked and maybe even check the indoor coil. Even though you have an 8 seer and a 13 I don't think it should be doing this.

Tom, I wouldn't like that explanation either. Doesn't make sense. Why after all these years? Next time blowing warm air open air handler, probably see that it is frosted or frozen up.

No A/C tec as you well know.

Tom, best I can offer is a tub of assorted beer on ice, or iced tea if you're a tea toter.

I been in Florida in July, once, that is ridiculous. My fingernails were sweating.

That heat is only good for alligators. Never again.

If I had an AC I would send it to you. No need here in Maine.

No expert on AC here, but I agree that dirty or iced up coils sounds like the problem. My window unit, when I lived in Ct, where AC is definitely needed, would ice up if I had the stat set too high.

Maybe a call into another, more reliable, service company is in order.

I sure hope you get cool soon.

I would agree about the dirty coils if this had just started but It's been going on since the installation. It just started blowing room temp air. I checked the handler coils and they weren't even cold. The compressor simply stopped running and in about ten or fifteen minutes I'll have cold air. But the place really warms up in those fifteen minutes.
The air handler was the same as installed in condos that were about the same square footage as my house . Two ton as I remember which is the same size as my compressor.
Are air handlers rated by Seer and should the difference between 13 and 8 Seer cause the problem I'm having? What can I outside of drawing a tub of cold water and sitting in it sipping a cold one? I want to thank you for all the response.
Tom

Hi Tom. Believe it or not, Im an HVAC tech too. IF compressor is kicking off(does the condenser fan stay running?) IF so, (and if you are posative outdoor coil is clean) Im afraid you will have to get someone to put some guages on the system. Since you say this has happened from the start, I suspect a possible overcharge, causing compressor internal overload to trip. Does this happen on all days, or just the really hot ones? It just really sounds like the compresser is working to hard, tripping overload, cooling off and restarting. Partial blockage in system(usually at metering device) will cause this also. One quick way to see if to get some gauges on the system. Wish I could help more, but you now how it goes. Please let me know what you find. Lee

First a 13 SEER outside unit can be hooked up to a 8SEER indoor air handler coil BUT the efficiency will suffer, To do this properly you should have a expansion valve on the indoor coil to allow the system to operate at it optium efficiency. Now just adding the expansion valve will not make the indoor coil operate as a 13 SEER style unit but it will help it to be all it can be.

Naturally this is not recommended since a 13 SEER unit should be hooked to a indoor coil rated for use with that unit so using a old coil will work just not real well for energy efficiency.

The new outside unit should not cut off at all as long as there is a call for cooling and the system charge is correct for the 8 and 13 SEER combo unless there is some other problem with the unit itself.

Questions

When the unit cuts off exactly what does it do?
Does the compressor in the unit stop running and the fan stay on or does the entire unit outside shut down?

If the contactor in the unit is opening and shuting the entire unit down then the low voltage signal source is being disrupted or is being cut off by some control somewhere. Naturally this can be tracked down and the problem eliminated.

If the compressor itself is shutting down but not the fan then it could be a weak component or the compressor could be going out on the internal overload.

When you say the unit stops cooling and then turns back on what is the time factor here? 5 minutes or one hour or?

If the circuit breaker was cutting the outside unit off you would have to reset the circuit breaker for the unit to start again. Are you resetting the circuit breaker or does the unit restart by itself?

If you can answer those questions then we can figure out if it is a low voltage control problem or if it is the compressor going out on overload.

Now it could also be the thermostat as strange as that seems. Naturally you can jumper out the thermostat on a temporary basis to eliminate that problem.

Who set the charge in this system? It could be a overcharge condition which would cause the compressor to eventually go off on overload.

There are many possibilitys so if you can answer the questions to see if we can narrow down what you should look for.

On thing I know for sure is that this is not normal so who ever told you that is not telling the truth.

NOTE No indoor coils are rated just by themselves. The rate of SEER is accomplished by the outside unit by using a known model indoor coil. The coils themselves are not rated. The newer coils are larger in size allowing for better cooling efficiency when used with the proper outside unit. The approved coils for usage with the outside unit get that way from enginering then testing to assure it meets the 13 SEER and above classification.

First, Thank you HVAC for responding,
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Quote:

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Questions
When the unit cuts off exactly what does it do?
Does the compressor in the unit stop running and the fan stay on or does the entire unit outside shut down?

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The compressor fan and the blower fan remain on but the compressor's not runniong.
2)

Quote:

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When you say the unit stops cooling and then turns back on what is the time factor here? 5 minutes or one hour or? If the circuit breaker was cutting the outside unit off you would have to reset the circuit breaker for the unit to start again. Are you resetting the circuit breaker or does the unit restart by itself?

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When the compressor shuts down it stays down for about 10 or 15 minutes and comes back on by itself. I don't have to reset anything
3)

Quote:

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Who set the charge in this system? It could be a overcharge condition which would cause the compressor to eventually go off on overload.

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The unit was charged at installation and last year My neighbors friend is a AC repair man and I had him put his gages on the unit. He said everything checked out normal.
What does a "expansion valve" look like and how would I know if I had one?
Thanks again for your help, Tom

The compressor fan and the blower fan remain on but the compressor's not runniong.

From your answer it seems the compressor itself if failing to run at all times when there is a call for cooling since the outdoor fan stays running. This means the contactor that controls the outside unit is working and the low voltage circuit is OK.

The one item that could cause this type of a problem is the internal overload that is built into the compressor. This item acts like an internal auto reset thermal circuit breaker that is designed to protect the compressor.

The compressor depends upon the low side (suction side) of the system tubing to return the cool gas to the compressor itself thus allowing the electric motor stator (windings) to stay cool in such a hot environment. (See picture and notice how the low temp returning refrigerant gas is flowing into the compressor and then around the stator (windings of the electric motor) then on to being compressed into a high temperature gas again. After being compressed into a high pressure gas the coils in the outside unit cools this gas to turn it back into a liquid for reuse in the cooling.
The internal overload is inside the compressor stator/windings so it is not a serviceable item. If this has been going on for a long time it is possible the internal overload has been weakened and if that is the case the compressor would need to be replaced to correct the problem. I am going to have more than one post to cover all the bases here so be patient.

The system could be over charged with refrigerant or undercharged.
The flow rate device piston, cap tube, or expansion valve could be the incorrect one for the size of the unit. (Normally this is checked by the installed during the install). To much refrigerant (Freon) or to little can cause the system not to perform as designed and this can cause what is happening to the compressor by allowing it to overheat due to lack of cool return gas to cool the compressor windings. The piston type device is a restrictor style and they all have different numbers for the different orifice sizes.

A weak or out of calibration run capacitor can also cause this problem. If the capacitor is not within spec for the compressor the motor in the compressor will draw over the rated amps and thus overheat the compressor windings. This is not a common occurrence and it is missed by many service personnel but I have seen it many times over the years. The run capacitor will be good enough to allow the unit to run but not good enough to allow it to run normally thus generating excess heat which in turn trips the internal overload in the compressor.

So what's your recommendation? How can this be fixed? IF you have anything more I plan on printing out all the posts that deal with the problem and take them in to the owner of the company. The owner's no stranger to me. 30 years ago he was the AC foreman and I was the plumbing foreman on several projects. So I maybe have a little edge . What do I tell him? I'm way out of my league when it comes to AC.
Thank you all for your posts. Tom

Got busy today sorry about the delay.

Without having an on site look at your situation I will list what I would do if the unit were mine. You will have to take into account that my labor and other stuff would be free. I also would not have waited so long to take action but as you said you were lied to and it all was blamed on the old 8 SEER coil if I remember correctly.

It is a good possibility the internal overload has been damaged in the compressor. Usually when they have reset so many times the overload will become weak and will trip out at a much lower temperature than what it was originally set for so I would replace the compressor while it is under warranty. As cause of failure I would list a damaged internal overload and here is the rest of the list of things to do.

Replace compressor

Remove factory liquid line drier (if so equipped) and install a new liquid line drier. (This way we will know the system will be clean and debris free.)

Replace the expansion device with an expansion valve OR replace the entire coil with one designed for the newer outside unit and the new coil should have the correct metering device or expansion valve installed also.

Check the compressor run capacitor for proper capacity plus or minus 6% maximum of the listed reading. If out of spec replace.

Add the following to the unit since an expansion valve has been added.

A five minute time delay on break component (helps to prevent the unit from short cycling and helps save the new compressor.

A factory start component kit designed for the new outside unit. This will consist of a start capacitor and a relay. OR you can also use a universal hard start device (kick start and other brands but I do prefer the separate factory kit with separate relay and capacitor).

The next item will be the most difficult to do.

Find a qualified service person to do all the work. Not your neighbors buddy or the guy down the street. I mean a real service person who knows exactly how to do the work and also takes great pride in there work. There are many Freon Jockeys out there and you want to stay clear of them. All good refrigeration practices should be followed. IE purge, vacuum, nitrogen flow while brazing (which most do not due). ETC.

The compressor could still be good but I have no way to tell from here and if I were there I still do not have x-ray vision to see it anyway since it is in the windings inside the compressor tin can.

This info being supplied by me directly attributed to your post and the items you posted that your unit is doing. A on site survey of the situation by a knowledgeable service person could turn up other items as the cause and cure but this is the way I see it from here.

I want to thank every one that responded to my question. Especially HVAC1000 for the extra effort he put into his answers. I'll be taking your posts down to the owner and will keep you informed of the results. Again, thank you so much. Tom

Anytime Tom. You have helped many folks out on the plumbing board so I am sure everyone here hopes you can get to the bottom of the problem and have a trouble free unit to keep you cool.