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Hello,

I am needing to install a 240V outlet for a welder in my home garage. Unfortunately, my home's breaker panel is full and I need to make room for a 30A 2-pole breaker for said welder.

I have a TM3215CCU panel installed in the basement of my home. From the documentation GE provides, all I can determine about this panel is the following:

T GE Indentification

M Main Breaker

32 Maximum of 32 1" spaces

15 150 Amps (total max current of panel)

C Combination surface/flash

CU Copper Bus

The only helpful information regarding specific breaker criteria that comes from parsing this model number is the fact that there are a maximum of 32 1" breaker spaces.

My question is: How many 1/2" GE THQP Thin style breakers will this panel accept? I need to install 4 thin breakers total in order to make 2 x 120V slots available for the 2-pole 30A breaker for the welder.

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As others say, this GE panel does not support the THQP, their unique type of double-stuff.

Yes, you are past the point of needing a subpanel because you are already consolidating circuits to make space. This is a great example of why 30 spaces is a desperation minimum for a house. Even 42 will leave you with only 7 spaces spare when you unconsolidate the basement circuit and add the welder. Too close to the bone!

That is a fine panel so just install another one right next to it, or wherever else you please. Now you have 64 spaces, and that's a happy number.

You could get clever and make the new sub a 225A, so if you ever upgrade service, you just swaperoo so the new one is the main panel and the original is the sub. Doing the forward thinking to make sure all the details are right is worth the attention of an expert.

Subpanels are well within the range of a well-read home improver. The sub is entirely cold until it is connected to the main panel, where it hooks up like any other load such as the welder you are about to install.


One last thing: we have searched high and low in Code and there seems to be nothing that disallows having as many receptacles as you want on a 30A circuit. So you absolutely can have the dryer circuit power both dryer and welder. Do not extend off the dryer circuit (do a homerun instead) if it is wired with 3-wire cable (hot hot neutral) to a 10-30 receptacle. if it is 4-wire (10/3+ground) cable then you can extend off it.

In fact that is a good safety upgrade to do anyway! The old NEMA 10-30 type receptacle is dangerous, that third pin is neutral not ground, and a neutral wire failure will electrify the chassis of the dryer. Switch the cable to modern 10/3, receptacle and cord to a NEMA 14-30, and sever the neutral-ground tie in the dryer.

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According to this link your panel DOES NOT support the use of 1/2" mini breakers. If your panel is full, your only option is to add a subpanel. This will involve some work and I highly recommend hiring a licensed electrician. Also note, that your panel is rated for 150 amps.

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Your panel indeed does not support THQP (aka "thin" or "double-stuff") breakers

According to the catalog entry for the TM3215CCU, your panel has 32 full size slots and no half-size slots -- giving you 32 circuits maximum. There are three options available to you here:

  1. Have the service panel replaced with a larger panel (42 spaces minimum, preferably more, with 200A or 225A bussing and a 150A main breaker if you wish to keep your existing service size). This may be tricky, depending on whether your existing panel is surface-mounted or flush-mounted and what sort of wall it's attached to, and may require an electrician due to local code requirements. Considering that your panel is of recent make and in good condition, this probably isn't the greatest option unless you want to upgrade to 200A service while you're at it.

  2. Install a conventional feeder and subpanel, moving some breakers to the subpanel to make room for the feeder breaker. The downside to this is that it takes up a fair bit of space and requires the shuffling of circuits around considering that your existing panel is utterly full, but it is likely the best option unless you want to upgrade to 200A, as it allows you to put in an ample supply of spaces -- once again, 42 spaces for the subpanel with 200 or 225A bussing is not out of place here. (If you had my vote on what to move, the air conditioner breaker is a good candidate -- the lack of a neutral on that circuit means that you can "switch loop" the A/C wires back with the feeder conduit, and if you are mounting the subpanel so that there is less than 24" of conduit between the two, then you don't need to worry about derating either.)

  3. Have the existing panel interior swapped for the 32-space/42-circuit interior used in a TM3215C42 loadcenter. This would give you the ability to use double-stuff breakers in your reworked panel, but has the downside that double-stuff/thin breakers aren't very useful. In particular, the electronics needed for a GFCI or AFCI do not fit inside a thin breaker's frame, rendering them much less useful than one thinks. It also may be difficult to find the interior in question by itself -- you'll need to have an electrical supply house order it in for you if you go down this road.

Reusing the dryer circuit is an option

If the dryer circuit homerun is modern -- i.e. a 10/3 W/G cable with a NEMA 14-30R at the dryer end -- then you can tap into it for your welder receptacle, as there is nothing in Code that prohibits multiple receptacle outlets on a 30A branch circuit. The one downside here is that running the welder and the dryer at the same time will most likely trip the breaker, but given your situation, this may be the easiest thing to get you by for now until you can upgrade the panel. I would make this tap at the panel end, using 10AWG pigtails from the breaker and suitable connectors (such as wire nuts or 3-hole "Polaris connectors" rated for the wire gauges in question), by the way.

  • The best option for me at this time would be to tap into the dryer circuit at the panel - I have the NEMA 14-30R plug type. I picked up some 6-2 wire to run from the garage/welder to the main electrical panel, so the gauge is pretty big for wire nuts I would think. Is there some kind of screw terminal that may work better for tapping this into the dryer circuit rather than using wire nuts? Is there a guide on the best way to go about doing this? – Jacob Anderson Oct 9 '18 at 3:32
  • @JacobAnderson -- you are right that it's on the big side for wire nuts -- 3-hole mechanical setscrew ("Polaris") connectors are a better option for this – ThreePhaseEel Oct 9 '18 at 11:43
  • To be more clear - it sounds like the largest wire gauge I can use as a pigtail off the GE breaker is 10 gauge whereas my 6-3 wire that runs from my garage to my electrical panel is 6 gauge. I chose this size so that when and if I do run either a larger welder or subpanel, the wire gauge will support my needs. What is the best way to attach the 10 gauge pigtail to both the existing dryer wire as well as the 6 gauge run to the garage? – Jacob Anderson Oct 9 '18 at 11:44
  • The Polaris connectors seem to be a viable solution, but not readily available at your typical home improvement store. What I ended up getting were a pack of 6 gauge wire nuts. These 6 gauge wire nuts should fit (2) 10 gauge wires with (1) 6 gauge wire easily. I plan to bend the wire to accommodate the 3-wire connection as well as electrical tape the point where the 3 wires enter the nut so there is no tension at the point the wire comes together. – Jacob Anderson Oct 9 '18 at 19:34
  • @JacobAnderson -- you're best off checking with an electrical supply house for Polaris-type connectors (home improvement stores I've seen don't even stock the baseline 14-4 size sigh which is kinda sad, considering that they are far more universal than any wirenut you'll ever buy). The 10AWG pigtails will do for now, and I understand why you want a 6AWG homerun in case you put in a bigger welder in the future, but a future subpanel will go alongside the main panel in this case, not somewhere else. – ThreePhaseEel Oct 9 '18 at 22:31

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