Any Ideas as to What Could Have Caused this AC Compressor to Fail?

This requires on-site examination, there are too many variables involved to troubleshoot without hands on....I can tell you any general information, but need specific accurate feedback for certain things....You should have 1 sqft of return for each ton of a/c....The duct size is critical to proper performance, but the velocity of air flow can be manipulated to some degree....What is your geographic location? What is the brand and model number of your condenser and air handler?

The most common cause of compressor failure is low charge, leading to failed capacitor, leading to overheating of compressor, leading to wiring short or open circuit....

Thanks for the quick reply!

I live out side of DC. I will get the model # when I get home It is a Lennox. I can also give you the sq ft of the duct work.

I am interested to learn some theory. I am not too worried about duct size since it lasted for 9 yrs. If it lasts for another 9 yrs I will consider the unit doesn't owe me anything. The larger unit gets to the set temp much earlier in the evening than the smaller unit that didn't hit the set temp until some time in the wee hrs of the night.

I am still interested to learn about duct sizing. I am more interested it what might break a compressor after being shut down for a month or more and hadn't been used for cooling in 6 months. I do know the compressor is a scroll compressor. None of the techs are engineers even the better one told me he thought it was vapor not liquid that broke the compressor. I have learned a little theory can go a long way when trouble shooting.

Generally speaking scroll compressors are not damaged by liquid slugging the way hermetic compressors can be....Failure can be caused by many many different things, including failure to evacuate system and install filter driers when installed...Yes it could take as long as 9 years to fail.....Failure can be caused by lightning, fan motor failure, dirty filter or obstructed coil, either one...low voltage condition, bad wiring or connection, short cycling, bugs, snakes, lizards, frogs, ants, floods, corrosive environment, and the list goes on, sometimes there is no apparent reason, the windings in the motor had a thin spot of coating and arced, a piece of metal in the compressor had a contamination flaw....but the most common is as I stated in #1....

Did the compressor fail during the first usage for the year? How do you shut down and start up your system with season change? Your post indicates your in the MD/VA area, so I assume you have to change between heating and cooling operation. If you shut power off to the condensing unit during heating season, it's possible the crankcase heater was not on long enough to drive the refrigerant from the compressor can. Refrigerant in a dormant system will migrate to the coldest part of the system. If this is the compressor, it can result in valve damage from liquid refrigerant being forced through the discharge reed valve. It also could be a fatigue failure of the valve, or I've seen the discharge flex line inside the compressor fatigue (the compressor motor assembly is suspended from springs, and every start stop cycle results in torque of this assembly causing strain on the hot gas pipe), and cause circulation of the hot gas, until the motor windings overheat, and it does not draw enough current to trip any overload device.

As for the duct work sizing, have you considered a mini-spit system, or such (air handler in attic space). This would be a separate system from your downstairs, giving you a separate zone for the bedrooms. How is the hot air at the ceiling of the second floor returned to the evaporator. Without lots of air flow to your second floor stagnation is possible. A small fan can fix this by mixing the air at the ceiling, with cold air if this is delivered at floor level.

you have me shaking my head in disbelief. you have a lousy install, you will continue to have poor performance and continue to eat compressors until you get it set up correctly. your last compressor didn't just fail. you beat it to death. its really your choice, waste money and put in a new compressor in a known poor install. or stop the bleeding now and go back and get your airflow right, there is no magic trick here, I suggest you forget taking advice from a GC, and talk to a real AC contractor, NOT a reefer guy, maybe I have no idea what I'm talking about but my 35+ years in commercial ac service tells me I just might be right, the HVAC contractors license on my wall agrees. Fix your airflow or just keep shelling out money to guys like me

I'm with Fredski here. In my experience, many AC installers cut to the bare minimums (sometimes below) and rarely put in excess capacity. In my case, a 5 ton R-22 split system, they installed 7/8" suction tubing because the condenser and evaporator both have 7/8" fittings. But Carrier's installation manual says that even below 50' line length, the suction should be 1-1/8". And the ducts and filter registers sure aren't sized for any additional capacity. I'm not sure they didn't size the duct and tubing for 4 tons and then decide to put in a 5 ton unit. You haven't said what size tubing you have, you could have a similar situation. And what size are your main and return ducts? I think 16" diameter is minimum for 3 tons (don't hold me to this).

While you're looking up information, what brand was your old compressor and your new one? I think Milennium's had lots of problems - Copeland's seem to be better. When my Milennium went out after about 10 years, I cut it open and found the orbiting frame (it has a proper name, but I'm too lazy to look it up right not) which was made of cast zinc or aluminum, had broken and caused the compressor to lock up. Looking back, I'm pretty sure I had overcharged it, partly because of the original installation. It wasn't shorted to ground or, as far as I could measure, coil-to-coil.

I'd be sure and get the same model compressor as you got 9 years ago. Anything else may die much sooner under these conditions.

I have no expertise. I can find the thermostat and that's about all.

Thanks for the replies

Did the compressor fail during the first usage for the year? It completely failed once after 9 yrs. Over the first few yrs, sometimes we would get a freeze up near the air handler. I have learned to keep the fan on vs automatic to eliminate the frost. I have no idea if I had the fan set that night.

How do you shut down and start up your system with season change? We just turn the system off at the thermostat. It takes a rest for between 4 and 8 weeks. The power to the condenser is only shut off when there is a problem, which is usually every few years or less. This was at least 8 weeks. This was the latest summer we have had in 20 yrs. We actually had a fire about a week before it got hot. The compressor would be the coldest part of the system. It is in the shadows and outside.

How is the hot air at the ceiling of the second floor returned to the evaporator.

We have 2 returns. The top floor return might be 5 degrees hotter than the thermostat. They are near each other but the top of the return is almost 4-5 ft higher. The top intake could be as much as 90 in the day. It is in the hall which has no out vents. The other intake might be below 70 at any given time.

As for the duct work sizing, have you considered a mini-spit system, or such (air handler in attic space). This would be a separate system from your downstairs, giving you a separate zone for the bedrooms. How is the hot air at the ceiling of the second floor returned to the evaporator. Without lots of air flow to your second floor stagnation is possible. A small fan can fix this by mixing the air at the ceiling, with cold air if this is delivered at floor level.

Not necessary. Since the slightly larger air conditioner was installed, the cost of electric went up 30% then even more. I more than doubled the insulation in the attic. That was a super investment. The bedrooms are still a bit warm in the day 80+ but it starts to cool down as soon as the sun goes down. I normally have an attic fan. That is also dead and I bought 3 motors this time. By the time the motor dies, they don't make that model any longer. Then you have to find a compatible one. I got lucky and found 3 of what is broken on the internet and bought them all. I have 2 attics and 2 fans. Plus the attic is not load bearing. We were told not to store anything up there.

Our county is know for brown outs. I don't have to go any further than that. If that can weaken the unit we get them all the time in the summer.

The refer guy did not put in our unit; an authorized dealer put it in. I am not convinced that there was ANYTHING wrong with the installation. I am careful and like to even check out what a dubious person tells me. The person that said it was wrong was not from an authorized dealer and the company has a 2.5 star rating. The second opinion was also an autherized dealer 5 star rated also did not see a problem. Why get on my case for being a moron?

The freeze up of the evaporator coil and lines, particularly the suction or larger line, leading from the air handler, would most probably indicate a low freon charge, this would be congruous with probable cause of compressor failure, add to that the stress of brown out voltage conditions thrown in from time to time, would definitely take their toll...

The AC is on and fine. The start up was uneventful and only the compressor was shot. I have a 3 ton unit and 2.5 SQ ft duct. I am guessing the original unit was 2.5 ton. So the duct work is 16% undersized. Should I be worried about that?

Air handler CB26UH-036

Condenser 3006LO3864

That is too small, you need 3 sq ft as a minimum, I would go with a larger return, or possibly add an additional one, I like a 24" x 36" filter back return air grill on a system this size.... they make all sizes of filter back grills , and they are cheap and easy to install.......In any case the system will still work just with reduced output...If you do increase the return, you may need to add some freon, as the charge is set according to present condition....

Do yourself a favor and get a popular size so the filters are easy to find and cheap...

basically you can't have too much return air, the more you add (up to a point) the quieter the system will run without whistling

I suggest that you seriously consider checking the TX valve or other solenoid valves if they exist in the system.

If one of those is blocked or partially so, which could be indicated by the freezing, then lubricant is prevented from circulating to the compressor and it will fail.

The problem is your technicians ,there are a number of factors and components that contributes to the problem.Since you said for sometime now no cooling from the A/C ,if its a heat pump ,that means the reverse valve was stuck on the heating mode.If your machine is cooling only ,tell your technical guys to check their manfold gauges for possible pressure abnormalities in the system.Check both low and high pressure sides.I suspect your system have a partial blockage in the filter drier ,on the expansion valve or on the distributers.Check your duct if there is no loose VCD that can obstract the smooth air .Pumping efficiency of your comressor could be another fact.This can only be seen on the manfold gauge when your machine is running.You might wrongly condemn the compressor when its not the problem.

The circuit breaker is there to protect the cables downstream.

...as is the fuse. If either of these blows/trips, then it's time to correct the wiring fault before re-energising. If in doubt, consult a qualified Electrician.

I'm feeling generous for some reason today so I have a few more thoughts...you suspected a slug of liquid might have caused your problem. this condition certainly will cause mechanical damage, it was correctly pointed out that a scroll type compressor deals much better with a slug than s reciprocating compressor. but the real question is why did it slug to begin with? usually this is a piping design/install issue. you provided no pictures or technical data on pressures or temps, so we can only guess, I also wonder if your system has a crankcase heater, was it checked? is it wired in and online at all times?, this will also contribute to slugging.. and btw, the Carrier system with the 1 1/8 suction line is well known to people like me as a problem to recharge, you must weigh the charge, the standard refrigeration gauge method can throw you off . someone mentioned a TXV and solenoid valves, no pictures, you might have an Accurator, or other fixed metering device.....maybe even a cap tube or two. I am however sure you have an airflow issue and because of that you'll never have aproper charge or provide your compressor with the correct superheat to keep it at the proper design temp.

also an overheating compressor has nothing to do with your supply voltage protection that is provided in your circuit breaker. you're looking at the wrong end of the horse

Re: the Carrier 5ton R-22 suction line sizing. Are you saying the 7/8" suction line causes a problem, or a 1-1/8" would cause a problem? By the way, Goodman specifies 1-1/8 for 3-1/2, 4, and 5 tons, while Carrier specifies 7/8 for 3-1/2 and 4, and 1-1/8 for 5 tons. I discovered this situation while considering replacing my old R22 system with R410. I was curious whether the suction line could be re-used, since mine runs inside the brick veneer.

Thanks for all your help. I have a much better understanding of some of the issues surrounding my heat pump.

The system is silent other than a slight popping of the ducts as they pressurize. You can only hear that in the laundry room that holds the air handler and the ducts are exposed in that room. Changing the ductwork would be a huge job since most of it is between walls and floors. Labor is very expensive in this area and I am guessing the cost to swap out would be between 2 and 4 units. I doubt that I will be in this house for more than 20 yrs. The filter is the bottleneck for the duct system. By using a 50% less restrictive filter, I am more than compensating for the 16% reduction in ductwork. The company that installed the unit knew what they were doing or talked with the manufacturer before the installation to get their blessing.

Most of you understood my description of what happened between the heating and cooling cycle but not all of you. The climate was warm enough to turn off the heating in the beginning of April I didn't turn on the cooling till the end of May. The unit was at rest for almost 2 months because we didn't need it not because there was something wrong with it.

After reading all your comments, I suspect the compressor died of old age. I have one of the worst electrical suppliers in the US. Summers are plagued with brownouts and power failures. Letting the unit sit for two months might be a bad idea. Between seasons instead of saving a few $s on electric we can keep it running a bit. We may have to adjust the set temperature so the unit runs a little while each day. If the heat or AC fails we will know about it before the seasonal rush. Our summers begin hot and without notice. Everyone puts out grass seed in late March because summer starts in May. That way the new grass will live if summer comes in early May.

The wiring is fine. The original wiring was for very inefficient systems built in the 60s. The new system uses less energy even though it is a little bigger.

you might want to Google "barometric damper, eliminate your popping noise

Could have been an electrical power surge.

Could have been a starting capacitor failure.

Could be due to condenser fan failure or poor performance allowing the head pressure to get too high. (Very important to check this before you start the system back up.)

Could be 9 years of heavy use service wear.

Could be that the last service technician put the wrong or too much refrigerant in the unit.

Could be from too many compressor starts due to poor system design especially since you indicate that the electrical consumption was increasing.

Lots of possibilities all of which really do not matter at this point.

However if you really want to know the" root-cause" of failure send the compressor back to the factory for analysis. (If it is under warranty they will most likely require the compressor to be returned for testing and you can request a copy.)

$2,500 for a 5 Ton compressor? There are numerous outlets where you can purchase a high quality 5T Copeland scroll compressor for less than $500.00.

The high cost of repair is usually due to the labor required to remove compressor, clean the internal system, replace the compressor, then vacuum and recharge the system.

If you are making ice at the evaporator either the system was not charged properly or the air circulation across the evaporator coils is not of high enough volume. (Duct work too small)

Most units can be properly orificed at the inlet of the evaporator to limit the cooling capacity so that the technician can properly size the AC for the application.

Could have been an electrical power surge. Probably not

Could have been a starting capacitor failure. Both techs knew their stuff one just was 'sales driven' I can't imagine BOTH techs missing something like that.

Could be due to condenser fan failure or poor performance allowing the head pressure to get too high. (Very important to check this before you start the system back up.) The fan was working fine after the failure

Could be 9 years of heavy use service wear. Most likely - not so much of heavy use as multiple severe brown outs every summer and that we shut it down between seasons.

Could be that the last service technician put the wrong or too much refrigerant in the unit. This is the first servicing the unit has had other than occasional air handler cleaning.

Could be from too many compressor starts due to poor system design especially since you indicate that the electrical consumption was increasing. I never stated the electrical consumption was increasing. Someone asked me that and I said no.

Lots of possibilities all of which really do not matter at this point.

However if you really want to know the" root-cause" of failure send the compressor back to the factory for analysis. (If it is under warranty they will most likely require the compressor to be returned for testing and you can request a copy.) Great idea!

$2,500 for a 5 Ton compressor? There are numerous outlets where you can purchase a high quality 5T Copeland scroll compressor for less than $500.00. Yes I saw the exact model for $900. They gave me the wrong price in case the part wasn't under warranty. I would never have let them put it in for that.

The high cost of repair is usually due to the labor required to remove compressor, clean the internal system, replace the compressor, then vacuum and recharge the system. Labor is very high here because no one is handy and too many totally trust the repairmen. The installation was about a grand. I have been quoted $300 for a 15 min max job to replace a $22 part and another $300 to replace a sweat pipe valve that is very close to wood in a tight spot. I had replaced the part several times before but the supply stores have kept closing.

If you are making ice at the evaporator either the system was not charged properly or the air circulation across the evaporator coils is not of high enough volume. (Duct work too small) Yes the duct work is a bit small.

Most units can be properly orificed at the inlet of the evaporator to limit the cooling capacity so that the technician can properly size the AC for the application. What does this mean? Change the inlet orifice?

By now plenty was said, in good faith. I have no reason to believe half of it. But, badly designed ones can be repaired until the cows come home to no avail.

Two added factors. Low freon does cause bad freezeup of the coil, as only a lesser part does actual cooling.

The other comes from the left angle of a personal experience. An uncle and wife from the old world was here in one hot and muggy summer. Absolutely nice people. He was a professional gardener. She cooked something wonderful.

Well, one day I come home. The house is hot as Hades, and they are in despair, that they broke it. After a few question we walked down to the AC. Took the cover off. The ice was TWO INCHES all over the coil. By old country custom they "aired" the house, while the AC tried valiantly to keep it cool. The high moisture of the seaside air did the rest. A good hour of defrost, a bottle of good vine, and later closing the door did soothe the nerves.

MUCH LATER, it was all funny.

IF The operating conditions are abnormal, anything can happen, that the innocent owner have difficulty to settle with.

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By now, I do not even know, that compressor cut out on low pressure, or high, or Iust because.

Any chance you could separate the systems and put an air handler in the attic for the upstairs separate from the downstairs unit? I understand that might cause problems if you have a gas or oil burner for heat.

No, the attic can't hold much weight. I am not going to redo the attic for something I think is a non issue. I do not have that kind of money nor would it pay for itself if I lived here till I was 100 years old even if the unit life is cut in half. I would also have to buy 2 new units. I would prefer to buy a smaller unit then just be hot. From all the info I have received I see the real problem is the electric not the installation. Our electric provider has performed so poorly they are under fire from the local govs. Brownouts are constantly frying something in our house in the summer time. We lose something almost every summer.

I clearly understand the rule of thumb 1 sqft of duct space for each ton but no one has given me any clue as how that would hurt my compressor unless I keep getting freezeups in the evaporator. Note I have had one big freeze up in 9 yrs and that was 7 or 8 yrs ago. I understand how it could effect the blower in my air handler.

As I think back, the repair company had to OK a variant installation with the manufacturer for the installation to be warranted. We had to wait for an approval before we could move foward.

We have no heater we are warm enough that a heat pump works fairly well in the winter. I also had a second opinion by a tech from top rated firm in our area and authorized by Lennox. He couldn't see any problems with the installation.

This is the reason why highly experienced technician is recommended for this competitive job. You should have hired the professionals, then you wouldn't have required the two repair men for the job. Yeah, compressor costs nearly $2000 - $2500, but these technicians would repair it in an affordable rate.

I have a recommendation, you should hire technicians from amtekair, as they are known for their skills and precision time.