Wire Size For A 60 Amp Breaker ,.According To The NEC ??

[CADplans]

Is there EVER a situation where it is legal to run a 10 gauge wire into a 60 amp breaker?
I am not a NEC guru, but intuition would tell me that the answer is ,,,NO!
But, I am guessing, please help!

My heat pump air handler has two breakers on the front panel, they are rated 60 amps (both 220 volt single phase)

The installer wired from the electrical service with 10-2 wire to one of the 60 amp breakers.
(He did use larger wire to the other breaker, I could not find the wire size on that wire.)

Now, maybe, the incoming panel may have a lower rated breaker, which will protect the 10 gauge wire,,
but, if the breaker on the air handler is meaningless, I would assume there would be a disconnect, not a breaker.

The old air handler had fuses, so it had protection, I assume the manufacturer wanted the breakers on the air handler to provide protection?

So, is the 10 gauge wire, in this case, acceptable, or does the installer need to come back, and increase the wire to some size that is rated for 60 amps?

Thank you,,

 

[Damifino]

Not a electrician by no means...but that being said, I've always seen #6 copper when it comes to 60 amp.

 

[Diggin It]

The Duck quacks 6, or maybe 4 depending on distance.

 

[Slowpoke Slim]

Not an electrician, but I work with a bunch of them regularly.

My electrician buddy told me to run #8-2 for my new 50 amp breaker. There was an existing 30 amp circuit with #10's in the same location, but we ran this additional #8-2 circuit to the same part of the shop (new to me shop, wiring up my 220v compressor) to be able to use a 50 amp.

So if #10's won't work for 50 amps...

I'd say "No." to #10's at 60 amps.

 

[duffer]

It sounds like you have a similar set up as I did. A heat pump/AC condensing unit outside, and an air handler inside.

The heat pump requires anywhere from 30-60 amps depending on the load requirements. The air handler only has a squirrel cage fan to run, and possibly some emergency heat strips. A 10-2 wire is sufficient to run those. The 60 amp breakers on the air handler (?) may just be a convenience for hook up and not required.

Check your breaker box and see what the amps on the 220v breaker are for the air handler. Those control the inbound amps to the downstream load. If it's more 30 amps for the air handler breaker, you probably need a larger wire, like 8, or 6, or....

 

[Diggin It]

My heat pump air handler has two breakers on the front panel, they are rated 60 amps (both 220 volt single phase)

Now, maybe, the incoming panel may have a lower rated breaker, which will protect the 10 gauge wire

The bigger question here is the specs for the unit. If it has 60A breakers, the specs must call for it to be able to draw that high at some point. Smaller wire and lower rated breakers at the panel end might create performance issues or motor problems.

 

[LouNY]

What size breaker is feeding that #10 wire?
If it is a 30 amp feeding #10 going to a 60 amp disconnect for a 30 amp or less load your fine.

Also now many disconnects look like breakers but they are not breakers just switches (legal disconnects)

 

[CADplans]

It sounds like you have a similar set up as I did. A heat pump/AC condensing unit outside, and an air handler inside.
The air handler only has a squirrel cage fan to run, and possibly some emergency heat strips. A 10-2 wire is sufficient to run those.

The 60 amp breakers on the air handler (?) may just be a convenience for hook up and not required.

.

What size breaker is feeding that #10 wire?
If it is a 30 amp feeding #10 going to a 60 amp disconnect for a 30 amp or less load your fine.

OK, more details,,
This is a retrofit, of a replacement air handler.
Coincidentally, the 40 year old Carrier, and the new Trane look so similar, I would have bet both were built in the same building.

The old unit had big cartridge fuses, 4 of them, those fuses were as big as my index finger, they were white, with red lettering.
the new unit has two breakers exactly where the fuses were.

The original install had two sheathed gray cables, each as big as my middle and index finger, put together.
those big cables run from a dedicated panel twenty feet to the air handler.

I assume, the installer did not know how to connect those big aluminum wires to the breakers in the air handler,,
so, he mounted two disconnect boxes above the furnace, big aluminum coming in, small copper coming out.

So, I have huge, like #2 aluminum for 20 feet, then #10 for a few feet,, then into a 60 amp breaker.

Here is my concern, Suppose, this installer hits the lottery, and in 5 years, he is GONE, sitting on the beach, earning 20%,,,

The breaker in the incoming panel goes bad. a new guy looks at it, and says,
"OH the breaker went bad, because it is too small, this #2 wire needs a 60 amp breaker,,,"

Now, I have a 60 amp breaker, feeding #2 wire, that is then reduced down to #10, then connected to a 60 amp breaker.

To me, I could EASILY see that happening, and then the few feet of #10 wire,, it becomes a fuse,,
the #10 wire overheats, and burns the house down,,,

A 23 year old SW Virginia electrician , in the year 2025, is not gonna check the load on a wire that is coming into the main box.
He is gonna look at the wire size, and think the #2 wire needs a 60 amp breaker,, and he pops it in,,,

I think the #10 wire might be incorrect, but, I do not know,,,

 

[bnold]

Don’t care as much about the breaker in the air handler itself, those breakers are for protecting the wire in the AHU and have zero to do with protecting the wire feeding them from the panel.

Panel breaker is what matters. What is the breaker size feeding those wires?

If #10 is Hooked up to a 60A in your panel, that is bad news.



Generally AHUs with dual breakers are for splitting the stages of electric heat strips (either primary heat or secondary/emergency with a heat pump). The fan and controls in the unit are very low amperage. Heat strips can be low to high KW and should be indicated on outside of unit or inside a unit panel.

 

[LouNY]

Are you sure that the AC unit has breakers in it,
many of the newer disconects look like breakers but are not.
QO2TR - Square D QO2TR - 6A Non-Fused A/C Disconnect w/ Top Open (24V)
I could see your concern about a future electrician not checking the complete circuit out before replacing a breaker,
how is the old cable terminated in the original breaker panel to what size breaker.
Most of the time a 30 amp breaker does not have a lug capable of accepting #2 wire wire,
many will take a #8 as a maximum, unless it is given a haircut which is not a recommended procedure.