[theatretch85]

So I just had my furnace and air conditioner replaced in my new house and wired up a new A/C disconnect (the old one was in bad shape and was run with 12 gauge romex on a 30 amp breaker). The furnace guys told my brother that they couldn't turn on the A/C since the breaker for it was too big and it needed to be a 25 amp breaker to pass code/inspection. I kept telling them that they don't make a 25 amp breaker (not that I have seen in the US anyway) the 30 amp is the next available size.

Am I completely wrong here on the 25 amp breaker or am I right that this guy doesn't know what he's talking about? I already had intentions on re-wiring it once they were done, but I was just getting it hooked up for a temporary solution.

They also had problems with the 8 gauge aluminum feeding the disconnect box for the a/c, but the new whip I installed is 8 gauge copper. I figured the scrap 8 gauge aluminum from off the 40 amp stove circuit was a better fit on a 30 amp circuit than the existing 12guage wire that was feeding the old A/C!

 

[Grampa Bud]

I do believe those boys may be a little short on freon up there in their think locker. Take a look at the rating plate on your package unit. I'm betting the FLA rating is 25amps or close to it and they were using that for their breaker value. For 2 to 4 ton units, depending on their age of course, usually are carrying ganged 30 amp breakers around here. You are also absolutely right in getting rid of your aluminum wire. Copper is so much more stable and has much less resistance per foot resulting in less voltage loss; also current. The only good use for aluminum that I've found is beer cans and boats.

 

[Rivethead]

No - I did not know this existed either


5B723
Circuit Breaker,25 A
QO Circuit Breaker, Current Rating 25 Amps, Number of Poles 1, Minimum Wire Size 14 AWG, Maximum Wire Size 8 AWG, Plug On
>More Details...
SQUARE D
QO125 1Today

 

[HouseHelper]

25A breakers are available. And the 30A on the 12ga wire for the AC compressor could well have been correct as it is perfectly OK to wire HVAC equipment this way. Check the AC name plate.

 

[theatretch85]

Wow! I can't believe they actually exist! I have never seen where one has actually been in use or sold anywhere in local stores. The other problem I am going to run into, I still have this FPE stab lok panel to replace yet and I am not about to start buying breakers for that.

Do I really need to special order a 2 pole 25 amp breaker for this A/C unit to "pass" inspection on this? I can't imagine they require every other homeowner out there to change the breaker to 25 amps when most often the A/C breaker is 20 or 30 amps already.

Btw, the 12 gauge romex was fed all the way through the disconnect box and into the A/C unit.

Here is where the romex and two separate thhn style wires pass through the wall to the outside disconnect. The wires were fed through a short piece of PVC to use as a sleeve, and the romex returned through the sheetrock while the individual wires went up to the ceiling.

One feeds the A/C, the other feeds the downstairs bathroom (well they did)

The old disconnect box outside....

 

[williswires]

1) Please post a clear, focused picture of the nameplate on your unit showing the electrical data.

2) Please make sure that you fix the code violations in your panel as you do this work. For starters, the cables need clamps as they enter the enclosure - you can't just poke the hole and stick 'em through.

3) If you post clear, focused, higher resolution pics of your panel and installation then we can let you know of other safety issues that might be present.

 

[micromind]

I've installed quite a few 25 amp breakers. 1, 2, and 3 pole. For a 4500 watt 240 volt water heater, a 25 amp 2 pole is my standard.

I've installed 35 and 45 amp ones as well.

To connect an A/C unit, the amperage listed on the nameplate as 'minimum circuit ampacity' determines the wire size based on table 310.16, 75C column. The 'maximum breaker or fuse size' is exactly that, a maximum. You can go smaller, but not bigger.

It's common to have a larger breaker than the wire is rated for here. The wire is protected against overcurrent by the A/C unit, the breaker provides only short-circuit protection.

Rob

P.S. The standard breaker sizes are listed in table 240.6

 

[Stubbie]

As mentioned look at the units nameplate if it was manufactured after UL and the NEC mandated maximum breaker or fuse and minimum circuit ampacity these will appear on the nameplate. Like this.....notice you are allowed 40 amp fuses on 12 awg.

 

[theatretch85]

The pictures I posted are not how it looks now, thats how it was done by someone else. I have since removed the disonnect box and the 12 gauge wiring and replaced the disconnect box with a new one that includes the 20amp GFCI outlet in it for the service personel. The circuit breaker panel is on just the other side of the wall from the A/C disconnect, in fact the A/C disconnect is mounted next to the meter outside. The run of wire from the disconnect to the panel is less than 5feet.

I did not have a chance to look at the nameplate on the A/C last night as I had other things that needed to be addressed. I will try and take a look at it tonight and see what it says.


As for the GFCI outlet, can the wire for that run through the same 3/4" conduit as the wires for the A/C? In total there would be 3 #8 (could be 3 #10) and 3 #12 unless I can use the #8 ground for the GFCI as well, then it would be 2 #12 and 3 #8. In the pictures above, i'd be looking to run it out of the disconnect into the bottom of the panel crossing through 1 joist with just 2 90 degree bends, total length of the conduit section will be maybe 2 feet.

 

[HouseHelper]

As for the GFCI outlet, can the wire for that run through the same 3/4" conduit as the wires for the A/C? In total there would be 3 #8 (could be 3 #10) and 3 #12 unless I can use the #8 ground for the GFCI as well, then it would be 2 #12 and 3 #8. In the pictures above, i'd be looking to run it out of the disconnect into the bottom of the panel crossing through 1 joist with just 2 90 degree bends, total length of the conduit section will be maybe 2 feet.

You can run them in the same conduit, but why 3 #8 (or #10)? The 240V AC only requires two conductors. So you would have two #8 (or#10) for the AC, two #12 for the convenience outlet, and one #10 for the ground.

 

[theatretch85]

Well the ground I run will probably be a # 6 because I have plenty of green #6, I also have plenty of #12 THHN/THWN (dual rated), probably will just pick up a couple feet of #8 for the A/C hot conductors. I could use the 3/4" conduit as a solid connection back to the main panel as the ground for the whole box (A/C and the outlet), but I prefer to run the ground wire anyway. Plus this run of wire will be pretty short to begin with.

 

[theatretch85]

Ok, well per the pictures below, the minimum circuit ampacity is 15 amps, the minimum circuit fuse size is 20 amps and the max circuit fuse size is 25 amps. I think I will just install a standard 2 pole 20 amp breaker and be ok. If I have issues with the breaker tripping then I'll look into ordering the 25 amp breakers (which I am still baffeled that they do exist).

 

[Stubbie]

There you go... max fuse/breaker is 25 amps and minimum wire size is 14 awg copper.

I thought you were supposed to post a FOCUSED picture.....

 

[dSilanskas]

Of course they make a 25 amp breaker. Not popular but they do make one