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.
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
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 Wisnia (W1BSV + Brass Rat '57 EE)
"As long as there are exams in public schools there will be prayer in
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.
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 15aga, 20aga 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.
On 31 Jul 2004 14:48:30 GMT, firstname.lastname@example.org (Greg) wrote:
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
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.
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.
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