Heat Pump failure NEED HELP

Old 04-11-03, 12:24 PM
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Angry Heat Pump failure NEED HELP

I am new here and need help!

I have a Lennox Elite 3 ton electric heat exchanger (HP29) and I think the compressor just went south on me. It keeps tripping the breaker to it (30A, 240V) and has welded the contractor shut. I had a dealer come look at it and he said the compressor internally faulted. I am just naturally skeptical since it is a problem you can not see.

How can I verify his conclusion? I tried using my continuity tester in my multimeter and this is what I found. There are 3 terminals on the compressor, and I can get continuity between each of them and a ground (one of the copper pipes coming out of the compressor). I can also find continuity between any 2 of the 3 terminals. This seems like a sign of internal fault but I am not sure.

What are my option? I was quoted roughly $1500 to replace the compressor and roughly $1900 to replace the entire condensing unit. Is it in the right ballpark, it seems high to me but this is my first runnin with HVAC problems. I will be getting more quotes in the next few days hopefully. Can I get a different brand condensing unit installed on the Lennox system or is that a bad idea? Can the compressor be fixed? Any help would be greatly appreciated.

Thanks in advance,
Old 04-11-03, 01:59 PM
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If you have less than one megohm resistance between any terminal and ground you have a shorted condition in the compressor motor. It is done. Normally you take a reading from C to S and C to R and add them up and that should be the reading from S to R. But you are beyond that. From here it is a job for a professional. Make sure you get someone knowledgable. They should check the compressor oil for PH to make sure you don't have an acidic condition from a slow burnout.

The $1500 sounds high for a compressor. You will need to shop your locals for the best value.

Old 04-11-03, 03:51 PM
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The reading from a terminal to ground is only a good indication of compressor winding failure if all the wires are removed from the compressor terminals first. If you don't you could be getting a reading from any of the other electrical components.

When you are shopping for someone to repair your unit, ask them to include a new liquid line and suction line filter/drier.
Also ask them what micron level they usualy evacuate to and see what they say.
Old 04-11-03, 04:01 PM
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Thanks Greg. I failed to mention that and it is very important. Good idea on the deep vacuum. Anyone who gives you the answer in inches is not an ace hvac mechanic. I would look for someone who holds 1000 or less microns for 5 minutes and charges the system by weighing in the refrigerant. It is not as important on cooling-only units but it can make quite a difference in a heat pump. (My opinion on some of that)

Old 04-12-03, 05:17 AM
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Dear Scott--

If you're reading ohms to ground then you do have a compressor problem. No it can't be fixed since the compressor is hermetically sealed (in other words, the housing is welded shut).

While the replacement cost of the compressor is a bit high--in our area, a 3 ton compressor change out properly done runs from 950-1100 depending on brand--changing to a new outdoor unit is usually the better option if the old unit is more than 7 years old. You'll get a better warranty, increased efficiency and less chance of future problems with the system resulting from the current compressor failure. The pricing on the replacement condensing unit is in the ballpark.

Concerning the installation of a different brand...yes, you can have a different brand installed as long as the coil and refrigerant metering devices are compatible. I would recommend using an Armstrong or Ducane unit, as their simplicity and reliability is much better than Lennox eventhough both are part of the Lennox Industries (would have never thought the generics would be better than the parent company...go figure)

GregH and Kfield are right about finding an experienced reputable company to do the installing. Be sure they will install the proper filter/drier (both suction and liquid line for compressor only replacement...bi-flow liquid line drier if it's a heat pump outdoor unit replacement), evacuate the system, and charge the unit with refrigerant by weight (if you just have the compressor replaced) and then double checked by the superheat method (which is much more accurate than weighing in the refrigerant since it automatically takes into account changes in tubing length when done properly...much personal experience on that)

Check with your neighbors, co-workers and friends about who they use for HVAC work. Find someone local who has been around and licensed for more than just a few years, ask for references, and get at least three bids to help you tell whether or not your being over priced.

Wish you the best
Old 04-12-03, 06:05 PM
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hi. when you test the compressor terminals you should have continuity from one to another.you should not have continuity from any of your compressor terminals to the compessor casing this would indicate a motor winding short.in your question you stated the contacter had been welded shut, this could be caused by compressor failure or maybe something else.if you are comfertable dealing with electricity you can xxxxx xxxxx xxxxx xxxx xxxx.but keep in mind you are dealing with 240 volt and if you have locked rotor effect in your compressor it will pull alot of amperage very quickly potentialy enough to kill you so be very very careful.but any way by doing this you may find the compressor runs fine.or not.just a thought.

Moderator note:

poleaxed: Please do not take offense but what you are suggesting is extremely dangerous, especially if one is not intimately familiar with ohming out the load.
We only want happy DIY members, not dead or burnt ones.

Last edited by GregH; 04-12-03 at 07:12 PM.
Old 04-13-03, 11:50 AM
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Unhappy replacement

Don't screw around with it....replace the outdoor unit.....especially if it's a burnout! The carbon deposits are most likely in the reversing valve which is a critical component that will screw up the whole ball of wax! Then the compressor fails again shortly there after, and the tech says the compressor is covered, not the labor.... boy is that gonna cost.... Also is the contactor in the replacement cost? How about the return trip to change out the filter driers to regulars after the clean up?... If it's a straight AC then replacement of the compressor is no big deal, and even then I use a HH clean-up filter.... twice as expensive but much better, also if he does do the compressor, make the filter drier twice the required size, and he changes it out a few days later.... Do the replacement on a clear hot dry day to get the best result. Heat pumps are hard top get the charge just right and a nice warm day makes getting it right easier. Remember...charging the heat pump is done in the cooling mode!

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