Home Air Conditioner unit grounding .. any fix?

[Alex]

Hello everyone,

Monday night our AC unit (electric central air and heat) started making a strange squeeling sound (like a loose belt on a car) then acted like it was loosing power... going normal then slowing down then normal again, etc. I turned it off and called a local repair shop which I've used in the past.

They came out today, and after turning the break back on, the repair guy touched the outside of the unit to get a shock which threw him back a few feet -- he touched the outside of the unit, nothing internal. After turning the power back off he did more digging and said the compressor was grounding and either the compressor needed to be replaced or the entire outside unit needed replacing.

This AC is about 23 years old and a 3 ton unit, and though we didn't expect to spend the money now, we hoped to upgrade to a larger unit at some point as we hoped to convert our garage into another room within the next year.

Just thought I'd put this out there for others more experienced then I to review. As I said, I've used this company before, and I have no reason to not trust them... but before spending $3500 or more I just like to do some digging.

Take care --

Alex

[Paul A]

Whatever else you do, have the wiring to the unit checked. There is supposed to be a ground that should trip the breaker with a fault like that.

[DK]

No. There is no breaker on the ground and the actual breaker doesn't trip on a bad ground. It trips on excessive current thru the hot wire with the breaker on it and this situation is bad but it doesn't trip breakers.

[HeyBub]

Huh?

There are two moving parts - that could cause a screeching noise - in the outside unit: the compressor and the fan.

My bet is on the fan (a $300 item).

I'd have someone else have a look. It's customary, when a repairman doesn't know what's wrong, to replace the whole thing.

You may just have a burnt wire...

[Richard J Kinch]

The proferred diagnosis is consistent with what you've described. You've gotten your money's worth and more out of a 23-year-old unit, and it's time to replace.

You can search grainger.com to see what these units really cost uninstalled.

[Joseph Meehan]

At 23 years old, my vote it to replace it with a modern more efficient model. In the long run it is likely to be less expensive to do it that way.

[Paul A]

With a good ground (which is missing) the breaker on the hot wire(s) will likely trip on the short to the case that gave the guy the shock. (depending on the restance of the short)

In any case, with a proper ground there would be no shock.

[Tom Horne, Electrician]

And again the reason it did not trip the breaker is that a required Equipment Grounding Conductor is open or missing. The EGC, if present and intact, will fault out the circuits Over Current Protective Device (OCPD) by conducting the stray current back to the source so that the OCPD opens. In a properly wired and maintained unit that would happen the moment the fault occurred.