We currently have our AC ran to this breaker box:

enter image description here

It has a 2 pole 30a tandem breaker in there now: http://www.homedepot.com/p/GE-Q-Line-30-Amp-2-in-Double-Pole-Circuit-Breaker-THQL2130/100356511

We are looking at adding a ductless mini split which would need its own breaker, and from conversations, the box has the capacity to handle the 15a unit, but not the space for another breaker.

I've seen quadplex breakers used for this type of situation, but based on the breaker boxes sticker, I cannot find a quadplex breaker that would fit this.
Does anyone know if/what would fit?

If possible, I'd prefer to go this route vs a whole new breaker box to accommodate the single additional tandem 15a breaker.

Edit: Here is a picture of the breaker actually installed. enter image description here

  • Can you post a photo of the actual breakers in the panel? The THQL line uses half width breakers instead of normal double-stuff/quadruplex ones, which means that your description of the configuration sounds...confused to say the least. When you say "tandem" do you mean "two pole?" – ThreePhaseEel Jun 13 '17 at 3:15
  • @Harper -- I think the box was originally installed to serve as the AC's disconnecting means, hence its small size (most AC disconnects are this dinky) – ThreePhaseEel Jun 13 '17 at 3:58
  • @Harper -- also, it seems that the panel is using a full-width 2 pole breaker so it should have room for 2 more slots, however, the layout on this panel may not be the normal interleaved one... – ThreePhaseEel Jun 13 '17 at 4:01
  • (this was comment #2, I deleted to improve it) @ThreePhaseEel Yes, now the diagram makes sense. This is a 2-space micro-panel (well more of a breakered switch). It is able to use half-width breakers (he has a full-width 2-pole breaker) so 4 circuits. Whoever bought it was fairly shortsighted and now OP is paying the price. Hard as it is to swap a panel, better now than after you've added more circuits. I would suggest swapping it now for a 12 or 20, to not have that problem in the future. Spaces are cheap, way cheaper than regrets. – Harper - Reinstate Monica Jun 13 '17 at 4:02
  • Yeah, that makes sense, he's trying to turn it into a real boy, er, panel. But it's not replacing the A/C?? (sure be simpler if it was). My issue is: if a second load has arrived out here, will a third? And can the supply to this "panel" handle more load, because who brings out 6AWG to a 30A shutoff switch? (after all, both being A/C units they will presumably run at the same times, so the wiring/panel must handle both at once). – Harper - Reinstate Monica Jun 13 '17 at 4:05

This thing is a shut-off switch, basically.

Many air conditioning units have a shut-off switch near them. This panel is designed to be that, and also provide overcurrent protection, and optionally GFCI. It is a 2-space "panel" which is designed to fit exactly one 2-pole common breaker. (any of the THQL THHQL TXQL or QPF types). It is designed to provide a) a shut-off, b) overcurrent protection, and optionally c) GFCI to a single load. It'd be a great hot-tub shut-off.

GE's slick design with THQP and THQQP breakers uses a clever way to do double-stuff 2-pole breakers. Since it uses half-width breakers, it simply uses a 2-pole breaker that sits in the halfway position, one contact on each bus bar. Any number of 2-pole breakers can be stacked like this, if your panel is wide enough. which yours isn't. As such, the only supported 2-pole configuration with these breakers is the 2-pole THQP sitting in the middle, in the 2-3 position, with a half-width breaker on either side. You cannot handle-tie the two outside 120V breakers because GE is quite specific that these breakers have an internal common trip mechanism. Handle ties only assure common shut-off, not trip, so one side tripping could leave the other side energized - bad!

However GE doesn't seem to make a quadplex 2-pole for it. That makes sense. The whole selling point of THQP is to avoid the duplex/quadplex model entirely.

The bigger problem is your wiring.

This really nags at me: Why would someone run 6 AWG to a shut-off switch to a single 30A load? Makes no sense. An installer would install 10 AWG throughout, unless he was some sort of visionary genius, and if he was, he'd have installed more than a 2-space "panel"! So I deduce the wire back to the panel is probably 10AWG and cannot support a second circuit. You would need to replace it with 6 AWG to support a 23-30A main air conditioner and a 15-20A auxiliary load. In fact, in some conditions 12AWG would be legal here!

Given that you may have to replace all that anyway...

...you might go ahead and replace that tiny panel

Normally changing panels is a bugbear, but you've only got 2 cables coming in/out of it so far. So now's the time.

I recommend people get 2-3x the panel they think they need. In your case since you need 2 240V circuits (4 spaces), I'd say go for a 12 or even 20 space panel. Panel space is cheap, unlike regrets, and panels often come with free breakers!

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  • 1
    This is a good answer. We can make it simpler. Take a good look at the label in the picture top right. It clearly states in bold "4 poles only". That's not suggestion or a recommendation, it's an instruction. All other argument is mute – Retired Master Electrician Jun 13 '17 at 13:04

It says right on your breaker box label that to only use these types of breakers with that panel:

GE Types

  1. THQP
  2. THHQP
  3. THQL
  4. THHQL
  5. TXQL

Siemens Type

  1. QPF

So you will have to go search out an electrical supplier that carries these types or their equivalent replacements to see what is possible in your box.

The label also says that a breaker max rating is 80 amps.

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  • This doesn't really deal with the problem he's having though (trying to wedge a 2nd common trip 240VAC circuit into the box) – ThreePhaseEel Jun 13 '17 at 3:52
  • I see the types it supports, but none of those types seem to carry a quadplex model, hence my question of if the unit could even support quadplex. – Fuzz Evans Jun 13 '17 at 15:45
  • What is the maximum allowed size of breaker for the existing condensing unit? This will be on the sticker on the side of the condensing unit. Right now what is the size of the feeder breaker for this circuit in the main panel? – Jim Stewart Jun 13 '17 at 16:21

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