My central AC unit has the following product specs:
AC voltx = 208/230 Phase=1 Hertz=60
Voltage range min=197 max=253
Min Circuit Amps=22.7
Max fuse Amps or HACR Type Circuit Breaker=35

It is currently wired with AWG 10/2 and connected to a 220v/40 amp breaker. The wiring is approximately 4 years old and the breakers are around 10 years old.

Is the wiring size and breaker size correct? Is there any life span on the breakers where after a certain age they should be replaced?

Thanks in advance

Can't answer all your questions, but to my knowledge there's no normal "lifespan" for a circuit breaker like there would be for light bulbs (for example).

I've never had to replace a circuit breaker because it wasn't any good, but that occasionally does happen. Circuit breakers can go bad, it's just that it's not very often that they do. The time honoured tradition is to try replacing the circuit breaker if you can't find the problem anywhere else.

However, reading between the lines, if you're having a problem with your circuit breaker tripping as a result of your air conditioner going on, then I'd be inclined to try replacing the breaker. I know that in my building it was COMMON for tenants to keep blowing fuses with window air conditioners. The solution to that problem was to install "Slo-Blo" screw in type fuses in the fuse boxes for those circuits.

I really don't know if there's such a thing as a "slo-blo circuit breaker", but hopefully someone in here will.

This message has been edited. Last edited by: Nestor,

Your breaker size does not match the AWG properly according to the NEC. A 40amp breaker will need to have #8 copper to be sized correctly. I also wonder why 10/2 is in place as methinks 8/3 should [if Romex] be in place for a 230v feed. I might be missing something via the net though.

An addendun. I think you should have this wiring setup checked by a HVAC tech. The more I think about the less confident I am about it. I have seen and wired more that and few units, but never wired one in the fashion you describe. As stated earlier, I may be missing something via the www, but when in doubt call a pro.

quote:

Originally posted by CommonwealthSparky:
Your breaker size does not match the AWG properly according to the NEC. A 40amp breaker will need to have #8 copper to be sized correctly.

Not at all true, especially for an A/C unit.
What part of the NEC are you referring to?

quote:

I also wonder why 10/2 is in place as methinks 8/3 should [if Romex] be in place for a 230v feed. I might be missing something via the net though.

An A/C condensor with a MCA of 22.7 is perfectly fine on #10. Also, WHY would you suggest XX/3 wire? A 240v load, like this condensor, does not require a neutral.
Again, 10/2 would be typical. You say you've wired a lot of these units. Do you always run3-wire?

Now, the 40A breaker is a violation because the Max fuse or breaker listed for the unit is 35A. I bet the installer could not find a 35 and put in a 40.
A 30 would still be fine and likely not trip.

Are HVACs wired with a neutral present ? In these parts they always are. Surely a regional thing. With out one the circuit would be flagged in a nanosecond. But we also factor in a 125% overload taking into consideration a HVAC also has a defrost cycle load as well.

quote:

Originally posted by CommonwealthSparky:
Are HVACs wired with a neutral present ? In these parts they always are. Surely a regional thing. With out one the circuit would be flagged in a nanosecond.

I know that PA is very much parallel to NY State with regard to many things. That said, I have NEVER seen a typical split-unit central A/C condensor that required a neutral.

quote:

Originally posted by CommonwealthSparky:
But we also factor in a 125% overload taking into consideration a HVAC also has a defrost cycle load as well.

You mean you figure in another 25% on top of the rating plate MCA? WHY???

This message has been edited. Last edited by: Speedy Petey,

In my experience that is fine ! I see no reason 10G wire wouldn't carry the load. A 40A breaker is actually oversized, should be 35 but the installer probably only had a 40 with him. In most instances a 30 would be adequate.

I heard what you are saying, but will your inspectors not require a neutral and ground for the control circuits to be complete ? I realize that it may be 10% or less in total power consumption, but 100% important as well.

Question from The Red One:
"My central AC unit has the following product specs:
AC voltx = 208/230 Phase=1 Hertz=60
Voltage range min=197 max=253
Min Circuit Amps=22.7
Max fuse Amps or HACR Type Circuit Breaker=35"

The voltages in residential electrical services (in USA) are correct. The nameplate on the A/C specifies the minimum circuit required is 22.7 amps. A 10 gauge copper wire is rated at 30 amps. So the wiring is sufficient. The circuit breaker should be down-sized to a 2-pole, 30-amp breaker becasue the 10 gauge copper is RATED at 30 amps, AND the AC specs indicate 35 amps MAXIMUM fuse or HACR type breaker. Nearly all modern 2-pole breakers are HACR rated.

If a circuit breaker is installed properly in a relatively temperature stable environment and average humidity, it should not need to be replaced after 7 years. Of course, this point is moot in your case. You need to change the breaker to match the amperage rating of the wiring.

In response to an additional point added to the discussion, a neutral is NOT required on a balanced 240-volt load, which AC compressor units are. (At least EVERY one I've connected in the last 34 years has been.) If a neutral were required, the manufacturer would have indicated such in the wiring diagram.

Good Luck
Gary K
Licensed Electrical Contractor