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Mike Lamb

A/C compressor unit clicking - Split system

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In multi unit buildings the AC compressor units are usually all bunched together outside with no identification. I know they should not be run in cold weather but I have started in the last couple of years to briefly turn them on so I know which one belongs to the condo I am inspecting.  I use my cell phone to communicate with my client and when the compressor fan comes on I tell them to shut it off so it is never on for more than 15 to 30 seconds if that.  It is my understanding that running them briefly in cold weather will not hurt the compressor. Today it was about 40°.  I had my client turn on the AC and all I got was a loud click at one of the compressors. No fan. I waited about 20 seconds and told him to shut it down, and again I got another loud click. What do you think this means?

P4030298 AC.JPG

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I just received this remark from an HVAC forum where I asked the same question:  You have a big set of onions doing what you did. Most times the compressor WILL BE DAMAGED by starting in cold ambients.

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When it's much colder outside than inside, the refrigerant will condense there, on either end of the compressor.  Conditions most likely to result in damage to the compressor are: a larger portion of the condensed refrigerant is inside the hermetic unit (at the compressor intake) instead of in the condenser coils (at the compressor discharge); it's a piston unit instead of a scroll; colder temperatures.

I don't see how anyone can say that a certain condition is gonna blow the compressor.  Factors have to add up to get that perfect storm.  As for the clicking, if it was the compressor capacitor, the fan would have started.

Compressor contactor is all I can figure out, in regard to the clicking but I'm a little handicapped in that department.

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Lennox scroll compressor units have one dual capacitor for both compressor and fan. When the capacitor fails, nothing runs. 

Not worth fixin' - it's 19.5 years old. Most Lennox HPs from that era usually don't make it to 15.  

 

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1 hour ago, Marc said:

When it's much colder outside than inside, the refrigerant will condense there, on either end of the compressor.  Conditions most likely to result in damage to the compressor are: a larger portion of the condensed refrigerant is inside the hermetic unit (at the compressor intake) instead of in the condenser coils (at the compressor discharge); it's a piston unit instead of a scroll; colder temperatures.

I don't see how anyone can say that a certain condition is gonna blow the compressor.  Factors have to add up to get that perfect storm.  As for the clicking, if it was the compressor capacitor, the fan would have started.

Compressor contactor is all I can figure out, in regard to the clicking but I'm a little handicapped in that department.

Trouble with the compressor contactor is also suggested on the HVAC forum.  And about a half-dozen other remarks that I'm an idiot and that home inspectors in general are idiots.

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It's possible, but difficult to damage a scroll compressor by running it in cold weather. 

It's much easier to damage a piston-type compressor in cold weather and the first few seconds will be the moment when it happens as the pistons try to compress fluid. 

 

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Mike,

 

Just for the fun of it, where is the low voltage transformer? On a split system, when you call for cooling, doesn’t the outdoor relay/contactor click on even if you don’t have power to the unit?

 

If there is no power to the unit due to a blown fuse or circuit breaker being turned off, I suspect that you may still hear the contactor turning on or off.

 

Jeff

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3 hours ago, Jim Katen said:

It's possible, but difficult to damage a scroll compressor by running it in cold weather. 

It's much easier to damage a piston-type compressor in cold weather and the first few seconds will be the moment when it happens as the pistons try to compress fluid. 

 

It's the reed valves that go bad when liquid refrigerant enters them.  Blows them right quick.

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