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I have a 60 amp circuit in my garage with one outlet that was installed by the builder. I want to use that circuit to have a 30 amp outlet for a welder and 20 amp outlet for a table saw. Can I use the wires feeding the current 4-wire outlet to install a sub-box and add a 30 amp and a 20 amp circuit? They would feed their corresponding outlets respectively.

Skipper
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2 Answers2

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The big question is what you currently have as a 60A outlet. But assuming that you don't actually need 60A (or 48A continuous) from that outlet, the usual solution is to replace the single outlet with a subpanel. 60A is a typical feed for a subpanel. In that subpanel, you can have any combination of:

  • 15A and 20A 120V circuits for convenience receptacles (tools, chargers, garage door opener, etc.) and lighting.
  • 20A or larger 240V circuits for tools, EV charging, HVAC, etc.
  • 20A or larger combination 120V/240V circuits for dryer or other things that need both 120V and 240V

There are a lot of rules for subpanels. But some key ones getting started:

  • Space, the final frontier - you need a 30" wide x 36" deep empty space - no permanently installed anything in that space, and no shelving, major appliances or other semi-permanent stuff either
  • Neutral and ground need to be kept separate in the panel. Typically panels sold as subpanels will have this by default (but make sure) and panels sold as main panels will have ground and neutral bonded (but make sure), but any new panel can be used either way. Just make sure neutral not bonded to ground/case and all neutral wires on the neutral bar and all ground wires on the ground bar.
  • Load calculation - You need to make sure that the expected load will fit in the designated 60A. There are ways to calculate this formally, plus informally by adding up all of the "constant" loads (EV charging, HVAC, etc. that could all be on even when nobody is doing anything) and all of the "temporary" loads (tools, lights, appliances, etc.)
  • A subpanel does not generally need a main breaker or disconnect if it is in the same building as the main panel. But it can be a good idea, and simply getting an inexpensive large main panel can make a lot of sense - a 30 space panel might not cost much more than a 12 space panel. Really.
  • Almost everything in a garage requires GFCI, except hardwired loads, though it does depend some on NEC version and local rules. GFCI can be provided at the breaker for 240V circuits and at the breaker or receptacle for 120V circuits.

Note that if you currently have a 60A circuit specifically for EV charging, you can install a subpanel and cut the EV charging back to a smaller size (e.g., 30A) in order to make sure you don't overload the panel, without having to actually replace the EV service equipment.

manassehkatz-Moving 2 Codidact
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  • What EV charging, the OP is not talking about that – Ruskes Dec 01 '22 at 21:38
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    Actually, OP doesn't say the current use of the circuit. But except for EV charging, 60A is an unusual size for a builder to put in a garage. – manassehkatz-Moving 2 Codidact Dec 01 '22 at 21:41
  • `30 amp outlet for a welder and 20 amp outlet for a table saw` – Ruskes Dec 01 '22 at 21:43
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    @Ruskes that's what OP wants to add. Doesn't say what is there now except "60A". – manassehkatz-Moving 2 Codidact Dec 01 '22 at 21:46
  • `Can I use the wires feeding the current 4-wire outlet to install a sub-box` would be pretty clear question, still no mentioning of EV – Ruskes Dec 01 '22 at 22:20
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    @Ruskes In most places, the EV charging circuit is installed as a matter of building code. A solution that eliminates EV charging capability may cause problems in the future, like if the house is sold or renovated. Therefore, it is valid to consider that. – user71659 Dec 01 '22 at 23:35
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    @user71659 Agreed. If it is required, you can't get rid of it - but you can put in a replacement. And I find it hard to believe a builder would put in a 60A circuit if it wasn't required. They don't even put in ceiling lights in bedrooms because they can save $20 by using a switched receptacle... – manassehkatz-Moving 2 Codidact Dec 01 '22 at 23:37
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    Wait, installing EV charging in a garage is now a code requirement? Sheesh! – FreeMan Dec 02 '22 at 15:19
  • Quite the nit pick from the guy who provided a "one sentence answer"... – FreeMan Dec 02 '22 at 15:20
  • @FreeMan It is gradually being added as a requirement. It is a somewhat interesting requirement, IMNHO, because while it promotes electric cars, it is an explicit strike against public transportation (which is arguably *far* more efficient and is also converting to electric power). At the price of new cars (i.e., even fossil fuel cars, for anything fully road legal in the US) if someone is going to buy a car they pretty much dump public transportation even if it is relatively convenient. (I have a public bus stop two blocks away and have used public transportation probably less than a dozen – manassehkatz-Moving 2 Codidact Dec 02 '22 at 15:32
  • times in the past year, and that was unusual - prior to that it was more like once or twice a year in the past 10 years, probably longer.) Why spend $20k or more for a car and only use it half the time. – manassehkatz-Moving 2 Codidact Dec 02 '22 at 15:33
  • Why have a car & use it only half the time? Because you live in Manhattan (NY, not KS). Source: My grandparents lived in midtown, owned a car, took the bus or subway everywhere. Would, occasionally, walk to the car to drive out of the borough. – FreeMan Dec 02 '22 at 15:49
  • @FreeMan - indeed, even if I had a bus stop outside my door I'd still have my truck. Hard to get to the middle of nowhere to go camping on public transport. But, the nearest bus stop is roughly as far away as my job, so... – Jon Custer Dec 02 '22 at 15:50
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    @manassehkatz-Moving2Codidact That sounds like a mix of crappy public transport with some sunk cost fallacy on top. I also have a car, yet I only use it rarely, because it almost never makes actual sense in terms of time efficiency. Living in a city with a decent public transit network, taking the bus takes about as much time as going by car (when you consider time spent parking etc.). However, time on public transport can be spent productively, while you can hardly do your e-mails while driving. Unless it's an hour-long trip with three changes, the car simply never comes out ahead. – TooTea Dec 02 '22 at 15:52
  • @TooTea I agree with most of your points. But that is the situation in, arguably, most of the US except in a few (but not all) large cities. A lot of people I know who live in those cities just don't own a car because the cost to park it is ridiculous. The solution *may* be Elon Musk's Robotaxi concept (you get to sit by yourself and go directly where you want to go) plus car-sharing services (far more flexible and affordable than traditional daily car rentals) but both of those do *not* need personal car charging locations - they would use central locations of some sort to do the charging. – manassehkatz-Moving 2 Codidact Dec 02 '22 at 15:57
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    Transport times in large cities with good public transport are roughly equivalent and usually better than driving. I spent a summer living & working in Manhattan with said grandparents. Walking, taking the bus, or taking the subway to/from work all took the same amount of time for me. The determining factors were weather, if I had something to read, how tired I was, and whether I felt like spending my $1 to save the walk (yes, it was a while ago). Taking a car would have probably taken the same amount of time there - there was a garage I could have parked in. Finding parking at home, though... – FreeMan Dec 05 '22 at 13:15
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Yes, that's not a problem. In the subpanel you will need to keep neutral and ground totally separate. That means buy an accessory ground bar (if it doesn't come with one) and remove any neutral-ground bonding screws or straps.

However, I am suspicious about your "60A" circuit since there is no such thing as 60A wire. I suspect you have 55A, 65A or 90A wire (90A is at a pricing sweet spot). While it's perfectly OK to have 55A wire on a 60A breaker, I would first want to know to see if I could use a bigger breaker, and second to know how much stuff I could power.

Remember - anytime you have a large 240V receptacle or hardwire junction box point in your garage, before you put your house on the market install signs that say "Level 2 EV charging". Home buyers go crazy for that! This isn't deceptive either: 20-30A is ample for EV charging if it's 240V.

Harper - Reinstate Monica
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  • Did you mean to say it's legal to have 55A wire on a 60A breaker? That sounds backwards to me. – Patrick M Dec 03 '22 at 04:31
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    @PatrickM yes, that's allowed because 55A breakers are not made. You are still required to assure the branch circuit or feeder load is (with normal derates applied) <= 55A. For instance for a continuous load, the max is 44A (x 125% = 55A). EVSE's typically don't provide a "55A circuit" option, so you are forced down to "50A circuit (40A actual)". – Harper - Reinstate Monica Dec 03 '22 at 20:01