House air conditioning problem

[chassis]

Hey folks,

Seems my compressor/motor is kaput. The house was hot last night, and the interior temp never reached the thermostat set point. Looked at my condensor/fan/compressor behind the house, and heard a humming sound. Though it might be the fan motor but no humming from it. I also tried moving the fan blades with a screwdriver to see if the motor would kick over. No dice. The fan blades spin freely with no drag.

The humming is definitely coming from the compressor. It is a Copeland Compliant Scroll. Couldn't see what displacement or model number it is.

Can anyone give me an idea of how much pain $$$ I might be in for? As a starting point, I would like to have an idea of the price for a compressor in the 1.5hp - 4.0hp range. I believe the refrigerant lines would also have to be evacuated, leak checked and recharged. Let's hope the reason for the compressor failure wasn't a leak, because the lines are run under my brick patio. :(

Thanks for any advice.

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[Davestone]

I've had this problem, and it was the little thing that kickstarts the fan..a small electrical part, only $100.00 for all.I'm obviously no a/c guy, though. :shrug:

[chassis]

Dave,

Thanks! Did you replace the electrical part, or did you have an HVAC guy come and do it? Hope that's my issue.

[Davy]

Yeah, it's hard to say. I've had the fan motor go out a couple times, had fire ants get into the connections and contact couldn't be made. My unit will be getting changed out next week, upgrading to a bigger unit, hope the electric bill doesn't bite too bad. :)

[cx]

Might be something as simple as a start capacitor, Will.

Or it could be the compressor, of course. The age and efficiency rating of the unit would dictate whether repair or replacement is the best option at that point. The newer 14-SEER heat-pump units pay out in seven to ten years when replacing an older 8 - 10-SEER unit in my part of the country, frequently with dramatically improved comfort in the living space. You'd need to check with a well-informed AC contractor for the cost/benefit ratio for AC-only (I presume y'all don't use heat pumps) units in your part of the country.

Davy: A bigger unit ain't necessarily a better choice for your replacement unless your existing unit was clearly undersized. You can have serious humidity problems with a unit that's too large in cooling capacity for the conditioned space. Gimme a call on the cell number if you like. :)

My opinion; worth price charged.

[jdm]

I second CX's sizing comments.

Remember that a big part of the comfort that A/C provides is from the reduction in humidity. When you walk into a stifling house and flip the A/C on, the house feels much better in about 15 minutes, during which time the temperature has only fallen a few degrees (if that), but the humidity has dropped dramatically.

But, the thermostat that controls the system responds to temperature only. Too large a unit can keep the house cool (once the initial cooling has been achieved) by staying on for too little time. The end result is a house that is cool, damp, and uncomfortable.

[NVC]

Hi Chassis,

Like the other gents have said, it could be a lot of things.

If the compressor is humming and it's just the fan not turning, I'd start with the contactor and verify power out to the fan/fan capacitor. It could just be the start cap as CX mentioned.

A fan motor and cap should be less than $200 (your labor)

'If' it is the compressor, yes the refridgerant needs to be recovered, a new one brazed in and vacuum pumped down and freon put back in. I don't know if they're still using R-22, but if not they would have a replacement (perhaps with a possibility of replacing the expansion valve at the A coil) but I think this was more for commercial refridgeration using R-12 and 502 (purple can, if I member right)

hope this helps,
Mark

[jjwq8]

Check if there is any ice on the outlet pipe. If yes then chances are your compressor simply needs refrigerant top-up.

Other than that it could be the stator/clutch. Anything electric and you wouldn't have power to provide a hum.

No clue as to costs.

If your insurance ar warranty covers it then liberal applications of a mancunian screwdriver will make you feel better even if it doesn't cool you off.

[chassis]

Thanks for all the input guys. I have some more data.

I took the outdoor electrical access panel off, and found the transformer (contactor?) is humming. I tried the old tapping with a screwdriver trick (plastic end ;) ), and it didn't help. Nothing else was humming except the transformer.

My thinking is it's the transformer/contactor. I'm going to see if I can source a replacement locally and replace it myself. It's made in the USA by "Products Unlimited", and to my eye looks like a transformer. I learned the whole compressor/fan/condensor unit was installed in 1998, so it's not all that old.

I guess the question arises - how can you verify it's not a bad capacitor? I have a Fluke multimeter that I'm pretty good with. What terminals can I measure to see if the right voltage is at the right places?

cx, yes some people here use heat pumps, but my house has electric a/c and gas forced air for heat, and no heat pump. You do heat your houses down there in that furrin land, don't you? ;)

[John Bridge]

Will,

I think you and I are at about the same level of expertise when it comes to AC. I was thinking tap it with a screwdriver. :D

[jdm]

Be careful around that capacitor. The start capacitors tend to be quite large and can deliver a dangerous shock from stored charge even when the power is off. The one in my Dad's unit died some years ago -- it sort of exploded and oil was everywhere.

I presume that the contactor you speak of is a relay that allows the 24 volt thermostat circuit turn on the 240 volt compressor. I would call the local distributor for the compressor to find spare parts -- that's where I've twice gotten parts (inducer motor and ignition module) for my gas furnace.

[Scooter]

Starting solinoid would be my first looksee.

[GraniteGirl]

Ours did the same a few weeks ago. Baffled everybody including the HVAC guy we had come out to look at it. Turned out it was the quick disconnect switch they install outside for the convenience of the service guy. The switch/plug thingy came dislodged when they were banging on the walls installing siding. A simple reseating of the switch fixed the problem. :stupid2: Talk about relief! Thought for sure it was something real $$$$$eriou$!

[Chris the Rep]

I wonder if the heating and air conditioning experts are at their on-line forum, speculating about the reasons for one of their owns' tile/stone problems?


Chris

[NVC]

Hi Chassis,

Chris :D

What Jeff said re: the cap. And only a meter that reads micro farads will do you any good, and few of them do. (Fluke does make 'em though) It needs to be discharged first with a screw driver across the terminals, but wait on that.

Odds are that if the hum was the contactor, it's engaged, and it's sounding more like a power problem as Granite Girl mentioned. Check the disconnect, it should be either fuses in there or a breaker.

If fuses, shut off the disconnect and pull 'em and you can meter 'em with the continuity tester on your Fluke (the setting that emits a beep when you touch the two leads together. Touch a meter lead on either end of the fuse and if it beeps, it's good.

If breaker, try turning it off, then on again.

If the power is ok at the disconnect follow it out of the conduit to the contactor (turn off aforementioned power first) If everything looks ok, I'd suspect the contacts on the contactor might be fouled.

Note: a lot of condensers have a time delay, which prevents people from turning on, then off, then on the unit (slugging the compressor) so if it starts working after an above fix, and you turn it off, then on . . . it might not come back on immeadiately.

hope this helps,
Mark

[chassis]

AC is working! :)

Granite Girl and Mark win the prize - it was bad power. One of the two 40A breakers feeding the contactor was bad. So bad that it completely vaporized the busbar lug on the panel. So I replaced the dual 40A breaker and moved it down a space so I have two good lugs.

The question remains as to why the lug was burned. I suspect corrosion, because I've replaced other breakers on this panel that were badly corroded inside the breaker as well as on the busbar lug.

So either I need to pull the busbar and replace it, or call someone to do it. Is it possible to replace just the busbar conductor as a stand alone component? It looks like it is a bolt-in affair, but have never done this before.

[jdm]

Glad to hear that the A/C is back on.

What make is the panel and how old is it? You should be able to replace the bus bar if you can locate a replacement.

Another question is why you're having corrosion problems. Is the panel getting damp?

You may be better off replacing the entire panel. If it's surface mounted (not recessed in a finished wall) it's not that hard to do. You may have to pull the meter to cut of the power above the main breaker in the panel.

[MHI]

The connector on the breaker must have been loose, and caused arching. The arching burned the bus-bar.:)

You may be able to get it replaced, or just replace the whole panel. Either way you have to get an electrician to do it.

You weren't thinking about doing this yourself were you? You have to pull the meter unless there is a disconnect on it. Otherwise you are working with live feeder wires.

[titmas]

My brother is a licensed electrician and does a lot of panel replacements. One of the many reasons that breakers and panels burn out is old age. Some go bad at 20 years and than some go at 5 years. But its the constant heating up and cooling down because of the heavy load put on the breaker is what causes the metal spring connectors in the breaker to loose its spring and arc out. Just short of a complete panel replacement, the next best thing is to replace any suspect breakers and use some anti spark gel on the connectors and the bus bar. Most electrical supply houses and even Home Depot carries the gel. I think the brand name is 'No-Lox'. It is possible to replace just the bus bar, but only if they still make the panel. Many brands of panels are no longer produced and part are hard to find. Good luck.

[NVC]

Hi Chassis,

I'm glad you're cool again. :cool:

It really depends on your panel. If it's less than 10 years old, and depending on the brand, you might be able to buy a new panel, and just swap out 'the guts'. I've never tried ordering a bus from the panel manuf. so I don't know if that is an option. (We would just replace the guts or whole panel)

Corrosion/oxidation can cause the connection between the bus and the breaker contact point to start arcing, which removes more metal, which makes the gap bigger, and more and bigger arcing, etc.

You might be able to give it a bit of a rehab, by killing the bus power, removing all the breakers, keep the wire attached and number them first, and give the bus a gentle scrubbing with a brass wire toothbrush, followed by a light coating of 'Noalox' made by 'Ideal' which is an anti-oxident/anti-corrosion goo that is conductive (hence a light coating and not making contact from bus to can) I don't know if the big-box stores carry it (elec. dept) but an electrical wholesale house would have it.

hope this helps,
Mark

[Davy]

Kelly, our old unit was undersized, we added a bedroom and gameroom on to the house about 10 years ago and never upgraded. The three ton unit would run all the time and never really get the house cool. I'm having a five ton installed with a two speed furnace. The guy that's installing it works with some of the builders I've worked for, known him for years and says the 5 ton should be okay. We did talk about the humidity problem with an oversized unit. :)

[chassis]

Thanks again folks. It will be nice sleeping in comfort, as opposed to the hot sticky oven we slept in last night.

I think Matt has it right. The breaker switch was completely floppy, no resistance or spring to it. Not sure why it got loose but I do believe the looseness caused arcing, which caused the eventual bye-bye of the bus lug.

Just checked my meter, there is no disconnect. So an electrician will have to come pull it.

The panel is readily accessible. Any idea how much $$ it would cost to have someone put in a new 200A 40-place panel? Ballpark guesstimate is good enough, I realize prices vary in different parts of the country.

[NVC]

We'd get $1200-$1500 here, but I think we're a bit steeper price wise in CA, because insurance, cost of living, etc.

It will have to be permitted if the power co. comes and lifts/disconnects the drops (overhead) because they won't reconnect 'em w/o seeing the final inspection OK.
Some electricians will lift and re-connect the power co drops, sans permits, because many cities (at least in SoCal) could 're-locate' the new panel, which I always thought was lousy, because it typically increased the customer's cost. Lifting live utility lines is definately NOT, a DIY job. It was 1 of only 2 things that would make me hold my breath. (which I never did, because permits were always pulled . . . :yeah: )

A few calls to local electrical contractors, and ask what an average range for replacing a service would cost, including permits, etc should get you closer.

I rarely say this, but replacing a service, is getting out of the DIY realm (I don't think you're thinking of DIY'n it, but just in case :)). Not that it's too technical or complicated, but rather too many variables that could make big differences if not accounted for. Because of the variables, it's hard to say via the Internet just do this, this and that, and it will work, because one size doesn't fit all and seeing something first hand is worth far more than a picture's 1000 words and what would seem like a minor mistake could end up making someone graveyard dead or smoking a plasma TV.
Sorry, if it sounds 'lecture'ish', not my intent. I just don't want anybody to bite off more than they might realize they're chewing.

Cripes, I'm exhausted. I feel like I just wrote 'War and Peace' :D

If you got to the bottom,
I hope this helps,
Mark

[cx]

All sounds like good advice, Mark. :)

I've never had a service entry replaced here, but I'd expect it to be more like about $800. I know I'd sure as hell try to replace only the guts if I were doing it. Gettin' all them wars out of the old box and into the new one, 'specially if it's an old installation, don't strike me as a fun day at all. :crap:

Glad you got yourownself back in service, Will. :)

Davy: I guess I shoulda knowed you woulda been payin' attention. :tup2:

[Tool Guy - Kg]

About $900-$1100 around these parts for a new 200 AMP panel. :)