15 amp circuit versus 20 amp

[Art]

The genius who installed the 3 ac units in my house 8 years ago reversed 2 and put a small compressor in the highest floor and a bigger compressor for the smaller finished basement. They switched the 2 when I pointed out the obvious mistake and they swore that they checked the inside units of each to make sure no other changes were necessary.

However for years, the slightest burp in electricity makes the circuit breaker go on the larger unit. Took me 8 years but it suddenly dawned on me that they did not move the breakers when they moved the 2 units. Sure enuf the smaller unit is on a 20 amp breaker and the larger is on a 15 amp breaker. Usually I have to reset the breaker for the larger unit 4 times a year when there is a blip in the power supply.

Anyway, I'm thinking that I should switch out the 2 breakers so they match the correct compressors respectively. My question is whether I need to worry about the wiring... would a 15 amp circuit and 20 amp have the same wire size... or is that another problem. I intend on examining the wiring but sometimes after 8 years it can be impossible to read the faded text.

Anything else I might be forgetting? Thanks.

[Greg]

The 15a could be wired with #14, the 20a should be #12. You can tell the difference just by bending the wire a little. To find out if your "big" unit can run on 14 ga wire you will need to read the plate on the condenser. It should give you the full load amps and branch circuit ampacity.

[Jeff Wisnia]

That's assuming you already know how it /should/ feel whn you bend it. And, only if the piece you are bending is virginal and hasn't been work hardened by someone bending it before you do it. So it's not really a very good measuring system....

If the OP can lay his hands on a micrometer or a vernier or digital caliper he can measure the wire diameter. 14 gauge wire has a diameter of .064", just a RCH larger than 1/16". 12 gauge wire has a diameter of .081". (Those dimensions are with the insulation stripped off of course.)

Jeff

[toller]

Code requires you to replace all cable that has faded beyond recognition. Good luck.

[Joseph Meehan]

As already noted, you can't just switch breakers, the wire must equal or exceed the size required by the breaker. In this case that is #12. With luck #12 was run for all three. Don't even think about moving a 20A breaker to a circuit with #14 wire.

I will add one additional note. Assuming you can move the breakers, you may still have the problem with the smaller breaker. That is because all the time it has been overloaded and tripped often enough that it may now be below specs and may trigger sooner than it should. If so just replace it.

[Red Neckerson]

"Art" wrote

Yeah. You forgot you weren't an electrician......

[Doug Miller]

What article would that be?

[Mle]

Those $1.98 Romex strippers have holes in them for matching wire sizes. Go to your local Ace or True Value hardware store, or HD or Lowe's or wherever.

Bob

[Travis Jordan]

Just out of curiousity, was this installation ever inspected? Any competent mechanical inspector would have found this right away.

[Greg]

That is not exactly true on a motor circuit. Under some circustances you can have up to a 40a breaker on #14. You size the conductor to 125% of FLA and you CAN use 310-16 for this, nort 240.4(D). (That is the 15a=14ga, 20a=12ga rule) These 430 rules are best intrepred by a licensed electrician but it is usually done for you in the manufacturer's instructions and the tag on a HVAC system.

[Greg G]

I use #12 whether the circuit is going to be 15 or 20A. The difference in cost is minimal, at least when you're dealing with the amount one homeowner is likely to use. I find #12 to be easy enough to work with and I lke the "headroom", should the current demand on the circuit be higher in the future. I can't help feeling that using #14 will cause me extra work someday.

I put in a circuit for an air conditioner in my kitchen with a 20 A breaker, but this time I used #10 wire, again in case I get a bigger air conditioner in the future and need a 30A circuit. I'd much rather spend the extra few cents now than open up my (plaster) walls again later.

Greg Guarino

[Jeff Wisnia]

Yes, I'd appreciate learning that one too toller. That might create some great business opportunities for those in the electrical installation trades.

Please tell us,

Jeff

[Jeff Wisnia]

A much better idea Bob...

Jeff (Whose tools are so old they don't have those niceties...)

[F.H.]

LOL, I'll bet you don't find RCH (the way you meant it) on acronym.com. To be more precise it's one and one half thousandths (.0015). 1/16 is .0625.

Frank

[Greg]

That was actually what I was hoping to be the case here. Why would an HVAC contractor carry 12 and 14? I wouldn't be surprised if it was #10.

[Greg]

If you can't feel the difference between #12 and #14 you might not have the dexterity necessary to swap the breakers.

[John Hines]

The electrical to a gas furnace, and A/C air handler is often handled quite well by a 15 amp circuit, which should be dedicated and unlikely to be expanded.

As always, in a pro job, the bottom line $$ counts. If money is not an object, then yeah you can compromise on the safe side if you like.

[Jeff Wisnia]

There I go, showing my age again. Aging is like a roll of toilet paper, the closer to the end you get the faster it gets used up.

Should I enlighten the young 'uns re that acronym?

Jeff

[mwlogs]

Maybe I'm missing something here, but should a breaker blow with the 'slightest burb' in electicity? My understanding was that the breaker was blown by the load placed on it.

[Art]

Well the compressor was supposed to be hooked to a 20 amp circuit but instead it is hooked to a 15 amp circuit which is clearly ok for normal start up and running but if the power blinks while the compressor is running the breaker is overloaded.