A/C Help...

[rjwaldren]

The A/C was out when I got home today, I need some tips before I have to call a tech out.

The blower is working and the thermostat will kick the compressor/fan relay but the one leg of the 240V condenser breaker pops at the panel. Last year I replaced the run and booster caps when it was doing the same thing. That got me through another year, but I doubt I'll be so lucky this time around. Last year had doubts about the circuit breaker that is again tripping. Both the fan and compressor run momentarily prior to the breaker tripping. Laster year , before replacing the caps the compressor just hummed and set there until the thermal protection circuit kicked in or the breaker popped.

I have 2 questions. First,what kind of DC resistance should I see at the compressor? Second, what size breakers should I have at the panel?

The Condensor unit shows the following:
Min Circuit Ampacity 33/33
Min Circuit Breaker 40/40
Max Circuit Breaker 50/50

At the breaker panel, I have 2 - 20 amp breakers - separated by 2 - 50 amp breakers for the stove. I can't get my head around it - but that doesn't seem right. In this config, do the 2 breakers add together to make 40A or is the plate on the condenser telling me I need 2 breakers each rated at 40 amp min at the panel. The wiring is fine for the later.

[Daryl]

You should have a pretty low resistance across the terminals I think.
Also I am pretty sure the breakers for the ac should be tied together so that if one trips the other does too. Other wise you run the risk of it sucking too much juice thru one leg and damaging your motor. Are the breakers on a separate buss? You should check your hard start and run caps to see if they are still working, maybe some moisture got to the terminals. You could clamp an ammeter to one of the wires and see how much current it is pulling.

[DUD]

I am not an Electrician, so that being said. I think You should have a single 40 amp breaker for 220Volt. It should be a single throw. Bill

[charliex]

You are correct in "that doesn't seem right". The A/C should be connected to a 220 volt 40 amp breaker,(the 2 toggles are connected, just like the one for your stove) not 2 individual breakers. From the amp rating it sounds like this unit is old. Mine, 8 years old is on a 20 amp breaker. Or maybe it is just a very large A/C.
Could be:
One of the fuses in the box by the A/C unit may be blown. (has a flip-up lid with fuses inside, There should be a handle that you use to pull the fuses inside) FIX Replace fuse. If one is blown I'd replace both.
Weak or bad breaker. FIX Replace breaker.
Unit is low on freon (or whatever it uses) FIX Get it recharged (pro work) and can be expensive. If it is really old, Replace unit with a new hi-efficency unit. Expensive but has a pay-back time if you live in a warmer climate. Many communities have an incentive plan where they reimburse you several hundred for replacing an old unit.
Hope this helps
Chas

[rjwaldren]

Daryl,

Yes, they are connected with a bar that looks to have a seen alot of use and no longer pulls both down breakers. That needs replaced either way. It the outer two breakers with 2 50A breakers for the stove in between, so yes the bus they are on separate buses. The breakers themselves are installed correctly I just question the rating.

I've read a few tips about some builders under sizing the breakers like this situation implies, (If I'm reading it right) I intend to replace the breakers as I have my doubts about them anyway. I just need to know if I should replace with the same 20A breakers or if the circuit should have had 40A breakers to begin with.

Unfortunately I don't have my clamp meter right now and I my Fluke DMM is only rated to 20A.

Charilex...

At the unit is just a bridge type disconnect no breakers/fuses.

[Hellrazor]

I'm the first person to check any A/C problems at work, before we get one of our contracted HVAC techs out. Bridged breakers can be a piece of junk and only 'half' trip. The bad news is that allows your motors/etc on a 220/240 unit to single phase which can and will burn up the motors.

The 33A is the max the unit should pull. You can't have 40A constant load on a 40A breaker or it would trip.

I am not sure how that would be running off a 20A breaker without serious problems. How long has the unit been installed like this?

[ssmith1627]

Make sure the wire can handle the load as well. The breaker is there to trip before the wire is overloaded. You don't want to replace a 20A breaker with a 40A and take away that protection unless the wire is rated for 40A.

Just my 2 cents.

Steve

[gjat]

Breakers can go bad as well. I'd replace the breaker and give it a go before calling a tech.

[rjwaldren]

Okay here's the deal. I was mistaken and the breakers are in fact 30A. Still lower than the data plate requirement, so they will need to be replaced. The existing wiring is sufficient. I'm don't know guages lower than 10AWG by sight, but it's a larger guage than the 50/50 circuit going to the stove. And it's larger than the Condensor wiring it is directly connected to.

It was installed by the builder in 2002. We've been in the house for about a 18 months. It's a basic 3 or maybe 3.5 ton split "Weather King" (Rheem off brand).

Last night I disconnected the fan and compressor and attempt to run them separately. The fan was fine, but the compressor stalls until the breaker trips. Last year replacing the caps got it through til now without issues. I'll replace the Start/Run cap tonight and see if it will go, that's cheap and quick. I'm not going to replace the aftermarket booster cap yet - It only there to keep a failing unit going. I'll have my Clamp Ammeter back tonight to. I know the breakers are under spec, but it seen the unit is the "bad" part, I'll upgrade breaker on my next day off.

Either way there's a tech coming out tomorrow to check out the unit. I have a feeling I'll be spending some money shortly.

Has anybody replaced a condenser unit lately? Did you get away with just replacing the Condensor/Compressor - Or were you pushed into a complete new system?

[crokett]

Not knocking the members of this forum but over on WN there are a few guys who work in the HVAC industry that hang out in the Home Improvement forum. You might want to post there also.

[cgallery]

Did you get away with just replacing the Condensor/Compressor - Or were you pushed into a complete new system?

I believe you get a pretty limited (short) warranty if you just replace the compressor. If the subject comes up make sure you find out what kind of warranty you get and don't just consider the difference in cost.

[rjwaldren]

The unit is undersized to the house and not an energy efficient model by any stretch, so the right thing to do is replace it with a larger one. I think compressor replacement would be the minimum required at this point that's if they can do it without additional work. A properly sized system would require complete replacement, but would likely pay for itself over time. I'll see what the tech says tomorrow, then decide where my repair/replace break point is.

At this point I hope to spend as little as possible upfront as we are stuffing as much money away as possible (baby due within 3 weeks, and an uncertian job future). Hopefully we can get it working through this summer, we know it needs to be upgraded, but it's a very bad time.