[sidejobjoe]

Well, I think I know the answer so kind of looking for an affirmation or some small miracle that I overlooked something .

So a relative of mine had HVAC problems with no cool. They called a tech out and he said the condenser (outdoor) unit compressor is dead and needs to be replaced.

Skeptical that a 5 year old unit would die like this (given how common compressor failure misdiagnoses is) I went to check it out for myself.

The symptom is, the condenser immediately trips the breaker whenever cool is called for. Just trips over and over again every time it is reset.

When I get there to look at it, I noticed the suction line insulation going into the unit is soaked (I mean soaked) in refrigeration oil.... 1st thought was uh-oh leak somehere in these brazed joints.

The capacitor(s) "looked" fine in that it wasn't exploded or bulging.

To cut to the chase, disconnected the leads running to the compressor (verified with the schematic) and measured the resistance....

This is what I got:

56 ohms between the start and run winding.....
56.5 ohms between the start and common.
.8 ohms between the run and common.

The .8 ohms suggests it is fried......

Yes/No?

Did I miss anything?


Thanks......

 

[roughneck]

Do any of the terminals ring out to ground?

 

[sidejobjoe]

Funny, I didn't test that... though I did think of it as I was driving away....

That would show if the winding is shorted to the compressor case, right?

 

[sidejobjoe]

Also, if it helps, the model number is RHP13410A36J.

 

[roughneck]

Funny, I didn't test that... though I did think of it as I was driving away....

That would show if the winding is shorted to the compressor case, right?

Yes, correct

 

[user_12345a]

check resistance between each pin and the compressor case.

if u get anything but open it's shorted to ground.

the refrigerant oil suggests a leak.

5 year old unit is worth replacing a compressor on, just make sure the cause of failure is rectified. I don't know what if anything can cause a compressor to short, just that it happens

would want the unit checked for leaks, bad capacitor, acid.

would want a new filter drier.

 

[sidejobjoe]

I will try and get out there to test that short to ground but given the resistance I got on the run coil and the breaker immediately tripping, what else could it be? Would a faulty run capacitor cause this? Could the resistance legitimately be .5 ohm (my leads are .3 ohms themselves)?

 

[user_12345a]

yes, if there's a short inside between those terminals, damaged insulation?

a short somewhere in the unit will do it.

condenser fan motor, wire damaged, touching the case.

 

[supers05]

0.8ohms is close enough to av dead short to me. (i call it phase to phase short as opposed to phase to ground) He mentioned that he disconnected the leads so that rules out the rest of the unit for that resistance. I would condemn that compressor too. If the unit was registered it should be under warranty. (You'll have to pay for labour though) It sounds like you have a major leak, and with it running with a lack of refrigerant caused the windings to break down. That will have to be repaired too. (A nitrogen purge and a new filter drier is highly recommended)

At 0.8 ohms, for a moment that compressor would draw 300A. (not accounting for sag and other electrical characteristics, at 240vac) That would trip breaker even if it was only a split second. (before inductance plays a part)

Cheers!

 

[beenthere]

5 year old unit is worth replacing a compressor on,

If it has a 10 year compressor warranty it is. If it doesn't, then it may not be worth it, since the new compressor will only have a 1 year warranty.

 

[user_12345a]

Unless there's something wrong with unit or system which killed the compressor, replacement compressor should last many years. less wasteful too for those who care.

Could also do a condenser-only change-out.

 

[beenthere]

Unless there's something wrong with unit or system which killed the compressor, replacement compressor should last many years. less wasteful too for those who care.

Original compressor should have lasted a lot longer then 5 years, but didn't. If a new one is installed, and the cause is not found. Then the OP gets to pay for a new compressor plus all cost of changing it out if the compressor goes again after the 1 year part only warranty. Very wasteful of the OP's money.

Could also do a condenser-only change-out.

Condenser only change out is an option. OP would get a 5 year warranty on the new condenser's compressor at least.

 

[supers05]

It's quicker to change out the whole condensing unit then the compressor. This will show up in the labour price.

Cheers!

 

[sidejobjoe]

I'm going to see if I can get at the terminals on the compressor itself to test the winding (if it has one).....but barring something extraordinary like a worn wire shorting to ground, something shorting the terminals at the compressor etc... looks like it is dead.

Been thinking about just replacing the compressor but it is somewhere around 5-6 years old so reversing valve could give out (heat pump), electronics etc.. etc.. so even if it is a bit cheaper it may be penny wise and pound foolish.

I just wish I looked at it earlier, the insulation soaked in oil would be a tell tale sign of a problem before the compressor died.

 

[BayouRunner]

Don't try the compressor any more. It's making a mess inside the system that will have to be cleaned up.

 

[user_12345a]

a matter of personal preference, i hate the throw-away society. what ever happened to a piece of equipment lasting 30 years?

5 years is nothing. better efficiency, but it gets offset by repairs and high labour costs.

 

[beenthere]

a matter of personal preference, i hate the throw-away society. what ever happened to a piece of equipment lasting 30 years?

Unfortunately, American society happened. People wanted things for less, but they also want paid more for their labor at their jobs at the same time. So manufacturers had to cut cost to pay higher wages and sell their products at a cheaper price, which meant/means using lower quality parts, and often having a low standard of quality control.

5 years is nothing. better efficiency, but it gets offset by repairs and high labour costs.

As a rule. If it was installed properly. Then it will last a long time. More then long enough to see/realize a ROI.

 

[supers05]

As a rule, i push my customers to change the reversing valve at the same time. It's only an extra hour and whatever the valve cost is. Other companies will be different though.

We've changed enough, and had reversing valves stick in less then a few months. (usually found on testing after recharging.) The windings will be breaking down. The resulting crud and carbonised oil from the arcing inside will plug the little pilot tubes on the reversing valve.

Cheers!

 

[beenthere]

As a rule, i push my customers to change the reversing valve at the same time. It's only an extra hour and whatever the valve cost is. Other companies will be different though.

We've changed enough, and had reversing valves stick in less then a few months. (usually found on testing after recharging.) The windings will be breaking down. The resulting crud and carbonised oil from the arcing inside will plug the little pilot tubes on the reversing valve.

Cheers!

Yeah, its a real bite if you change out a compressor on a heat pump, and then find out the RV isn't working. And was the cause of the compressor failure.

 

[user_12345a]

Unfortunately, American society happened. People wanted things for less, but they also want paid more for their labor at their jobs at the same time. So manufacturers had to cut cost to pay higher wages and sell their products at a cheaper price, which meant/means using lower quality parts, and often having a low standard of quality control.

Don't forget the corps maxing profit for their shareholders and the reasons why people need to be paid more and buying things for less in the first place -> aka inflation, especially in housing costs, health care, education. (all three turned into major rackets)

crony-capitalist rackets happened, big government & big business screwing people over

but i digress.