A/C Compressor Shutting Down Lennox HP21


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Old 04-28-16, 06:50 PM
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A/C Compressor Shutting Down Lennox HP21

HP21-60-230-03 outdoor unit
CB31MV-51 Air Handler

Unit is 16 years old or so. Compressor was replaced less than 5 years ago. WHole thing is way out of warrranty. Anyway, AC runs great all day long, on and off, sometimes all night long, then randomly, the compressor shuts off. Air handler continues to run. I can only catch it when I realize the air is coming out the vents but not cold. If I shut off all of my thermostats for a few minutes, then turn them back on, AC starts up and all is well until the next time.

This unit has diagnostic code led, and what I see is 1, 2, and 4 lit up, which means "7 Hot Compressor > 5 min. (or open sensor)".

I replaced all of my filters yesterday wondering if that was the cause, dirty but not THAT dirty. What can the cause be here?

Id like some input from someone other than my AC company because the unit has done this in the past, and thats why I had the compressor replaced. At the time I was told it could be the compressor is worn out, it could be this, it could be that....call up our customer service team and lets get you into a new system for 18,000 bucks!"

So...I expect the same kind of thing this time, but surely there is a way to diagnose and be SURE of the cause.
 
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Old 04-29-16, 04:08 AM
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It appears that the compressor is overheating and the thermal protection is kicking in to prevent the motor from burning out. While the cause could be one of several things, the first thing I would suggest you do is to clean the condenser coil. If the condenser coil is dirty, it won't cool as well which will make the compressor work harder. To clean the coil, remove the condenser fan from the top of the unit. Take a garden hose and very carefully spray water through the coil from the inside of the unit. In other words, you'll move the hose around inside the unit, spraying water so that it passes through the coil to the outside of the unit. Go around the entire unit, "backwashing" the dirt out of the coil.

Also be advised that another cause of the compressor overheating is the condenser fan stopping. The condenser fan serves a dual purpose: pull outside air through the condenser coil and expel it out the top, and secondly to cool the compressor.
 
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Old 04-29-16, 08:15 AM
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I checked the unit outside, the fan is working, and there isnt a blade of grass in the fins, they are all clean. Ill backwash anyway though in case its dust clogged. What about capacitors? Can those be bad and cause this? I have not tested them, but they were replaced last year. I have three. A big cylinder multi-capacitor, a smaller cylinder, and then there is an even smaller square-rectangluar one. What about refrigerant charge?
 
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Old 04-29-16, 08:24 AM
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We'll see. its a much bigger company than I first started using them. Used to, I knew all the techs and they were all good. That business model changed drastically, and I dont know them now. They dont stay long enough to get the same one every year. But at least this way, I know some potential causes and perhaps can suggest things if they dont do it on their own.
 
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Old 04-29-16, 08:50 AM
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It's remotely possible that it's a capacitor, however since they were replaced last year and the compressor & condenser fans startup, it's unlikely that is the cause. However, capacitors are relatively inexpensive if you want to try replacing them. When the A/C has been running for awhile, can you feel the temperature of the condenser fan motor? There's a chance that the fan motor is overheating, stopping the fan, and therefore making the compressor overheat, although that's a longshot.
 
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Old 04-29-16, 09:49 AM
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OK, so I have a plan of action, its been running for almost 2 hours now. The coil is not dirty, if its not capacitors, and the fan is still going, what ELSE could possibly cause it? What would the next step be?
 
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Old 04-29-16, 10:04 AM
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You will probably need external static pressure, indoor and outdoor delta t, superheat, subcool, voltage and amperage to make a diagnosis.

Measuring the capacitors and checking wire connections would be a place to start.
 
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Old 04-29-16, 10:07 AM
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I'm not sure what to tell you. You mentioned in your first message that the system often runs fine the whole day and randomly shuts down. To know what's really causing the problem, you'd need to check everything just before the system shuts down: is condenser fan running at normal speed? If there's nothing obviously wrong, you may have to call an A/C tech to come in and check the pressures. Perhaps that might give him a clue as to what the problem may be. Note that I'm going on the assumption that the compressor is overheating, since that is what the diagnostic LED's are showing.

Houston posted while I was typing this. Follow his advice, he's the pro, I'm just a homeowner.
 
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Old 04-29-16, 10:28 AM
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Cool

Cool. Will schedule a technician to come out. I am confident I have done as much as I can on my end. Time for a pro! Thank you all for your advice!
 
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Old 04-29-16, 01:41 PM
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Another thing I dont get is that the thermostats have been turned OFF for like 3 hours now, and the unit will not come on. The compressor is blazing hot out there to the touch. You can't hold your hand on top of it. Why is it hot when its not running!?
 
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Old 04-29-16, 03:32 PM
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The compressor should not be hot if it's not running. There should be an electrical disconnect near the outside unit. I would use it to kill the power to the outside unit and let the unit cool down.
 
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Old 04-29-16, 04:03 PM
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If the compressor is hot without running it may indicate a shorted winding. Many condensor units use a single pole contactor which keeps one leg of power on the compressor at all times.
 
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Old 04-29-16, 06:08 PM
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Tech looked at it. HEre are the bullet points of what I was told:

compressor is dying
Its coming apart on the inside
Its drawing 26.8A (which I saw on the meter)
Its a 30A motor, so its almost maxed out and its 75* out, so when it gets hotter, its going to draw more
Charge is low, which means it has a leak. Probably in inside coil. Coil is rusted.
Not good to recharge because more refrigerant will cause it to draw more power and just thermally shut off.
Its a 15 year old heat pump.


And...I need to call them about replacing with a Daikin system. Does this sound legit?
 
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Old 05-03-16, 04:39 AM
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Well, we have a diagnosis. I have had three people out to do it. Finally got someone that was able to diagnose and give me a real reason the things he wants to replace are needed. I trust the diagnosis. Its the first on that wasnt wanting to throw parts at it. Problem is the repair costs seems crazy high. I need a sanity check on it. Its like twice what I would have expected.

new TXV, filter dryer (there are two, both need replacement, one has restriction), new start kit, evacuate and all new R22 due to concern of contaminated system, test system after repair to verify correct.

How much should I expect for this?
 
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Old 05-03-16, 08:07 AM
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You need to get multiple prices. I don't give estimates here as the prices are all over depending on location, quantity and price of R22, difficulty of job.
 
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Old 05-03-16, 05:25 PM
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So, I figured out what the huge difference in cost was about. It has to do with the diagnosis.

TechA requires only the TXV to be replaced, which means they dont need to replace or remove refrigerant.

TechB says there is a restriction in the drier outside the unit as well, and that needs to be replaced. Recommends replacing BOTH driers since he suspects it has failed and contaminated the system. Suggests flushing system out and replacing R22 with new. Also says I CAN just do the TXV which will save money, but he is pretty sure based on what he sees that the rest should be done as well.


R22 is expensive. Labor is much more in time on the second repair and on par with how long I think it should take based on reading and others who have had the repair done. I do trust the judgement and agree, but thats based on taking his word that the drier is restricted.

One is cheaper and less involved, and the other is more thorough. Im leaning towards the more thorough one since I dont want to chance having to REFIX the txv if I dont clean the system. I can account for all of the cost with average R22 cost per pound and cheap labor rates. So, I feel better about it.
 
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Old 05-03-16, 06:07 PM
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If the system gets opened.... then the filters need to be replaced.
 
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Old 05-04-16, 03:30 PM
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Right. But the deal is, I am paying a HIGH dollar for replacing the R22 with new. This is all based solely on the premise that the filter/drier is 'falling apart' and has a restriction. So it's prudent to flush and refill with clean. However, I don't understand how one tech can possibly know if the filter/drier is 'plugged' without tearing it apart. There is absolutely ZERO temperature difference across EITHER filter drier. I checked with my hands, and I checked with my IR thermometer. 90-92 on BOTH sides.

This causes me great concern. Because if thats the test for it, then im being told a lie....a lie that is going to cost me about 1000 bucks more than the tech that told me exactly the opposite.

Tech A says there is absolutely no restriction in teh filter drier. The problem is ONLY with teh TXV. His method replaces that, pumps the r22 to the lower unit and requires no NEW refrigerant, saving me a ton of money.

So...which is it? How do I know who is giving me the run around.
 
 

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