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I bought a new Master Blaster that draws 18 amps when using both of its motors that I intend to use to when washing/detailing my car.

In my garage, I currently don’t have a 20 amp outlet. I have two 15 amp outlets and then I found a single large round dryer outlet that was rated for 30 amps and 250 volts. When I pulled it out of the electrical box, I found one black wire, one white wire, and one ground wire.

The part that’s confusing is that to shut off electricity to the black wire I had to flip one 15 amp breaker and to shut off electricity to the white wire, I had to flip another 15 amp breaker (see pictures). I’m guessing they added the two to get the 30 amps for the dryer plug.

I purchased a single (only one outlet) 20 amp receptacle that has a brass screw, a stainless screw, and a ground screw. Can I swap the 30 amp for the 20 amp without running into any problems? The single 20 amp info on the box says that the wires should by up to 10 AWG for this receptacle. I’m not sure if that’s what I have running through the wall.

I’ll likely use the 18 amp Master Blaster for maximum 10 minutes at a time with a 25 foot 12 AWG extension cord.

Is this wire setup in the wall up to code?

If not up to code, is this still safe?

Any issues with this setup (two 15 amp breakers for two different wires, the 20 amp single outlet, the 25ft extension cord, and the master blaster)?

Most important is, what do I need to do to set up the 20 amp single receptacle where the dryer plug used to be and not burn the place down?

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    It doesn't work that way, you don't add up two 15As to get a 30A. You stack two 15A@120V's to get 15A@240V. But this was done very improperly because of the overstuffing in this panel.
    – Harper - Reinstate Monica
    Oct 5, 2020 at 5:32
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    Yes. There are 2 exceptions: 15A receps are allowed on 20A breakers (so you can wire 20A circuits with common receps)... and 50A receps are allowed on 40A breakers (since 40A receps do not exist).
    – Harper - Reinstate Monica
    Oct 5, 2020 at 6:52
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    Just curious, was the original receptacle really a proper dryer outlet (NEMA 14-30, left one) with the neutral or ground contact not connected to anything (or worse, bootlegged), or a legal hot-hot-ground NEMA 6-30, or the old-school hot-hot-neutral NEMA 10-30?
    – TooTea
    Oct 5, 2020 at 15:27
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    As someone who has had to deal with 1/2 tripped circuits before (dryer was on two fuses, only one tripped, so it lit up and & spun but wouldn't dry) ... and then after getting panel replaced with circuit breakers, the AC was on two separate breakers, and it only one leg tripped when we attempted to rotate the outlet to fit a right-angle plug). It will save you a lot of hassle in the long run to get this fixed right, as it's obnoxious to debug when it happens.
    – Joe
    Oct 5, 2020 at 17:46
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    that doesn't look like 10/2 NM cable.
    – JACK
    Oct 6, 2020 at 0:26

4 Answers 4

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What a mess...

Assuming that your diagnosis is correct - two wires in the same cable connected to totally separate breakers, you have several different problems going on:

  • A 30A dryer receptacle should be on a pair of 30A breakers. This is 2 independent 15A breakers. You don't add (though it sounds logical) 15A + 15A to get 30A, because the 30A refers to 30A @ 240V. Each of those 15A breakers is actually 15A @ 120V. The two existing breakers together gives you 15A @ 240V.
  • Breakers for a dryer or similar 240V load need to be in a pair that trip at the same time. That is important for safety. As you already discovered, you could turn off one breaker but still have power in the box. If you had a dryer plugged in and it tripped one breaker but not the other, you might think there was no power in the box and get zapped while trying to fix it. The only way to do that properly is with a pair of breakers that are side by side and connected together (really "one device").
  • Most of your breakers are "double stuff"/"half size". That is not in and of itself a problem. However, a pair of breakers to provide 240V needs to be either 2 full size breakers side-by-side or the middle set of 2 pairs of double stuff breakers, as I believe is the case with the 40A pair in the lower left.
  • A dryer normally needs two hots + neutral + ground. There is a grandfathered way of two hots + neutral, no ground. Your cable just provides two hots + ground or hot + neutral + ground. My guess is that it was wired up using the ground wire as the neutral wire, since black & white were definitely hots. That is another Very Bad Thing.

So what you had before was:

  • Wrong size breakers - 15A instead of 30A
  • Wrong arrangement of breakers - not next to each other
  • Not common trip
  • Neutral on the ground wire

Basically, a disaster waiting to happen.

On to your new setup. You did not indicate if this is a 20A 120V device or 20A 240V device. My guess is that it is 20A 120V. If that is the case then:

  • You need to determine the size of the cable wires. My guess is either 12 AWG or 10 AWG. 10 AWG is what you need for 30A. 12 AWG is the minimum for 20A. 14 AWG is the minimum for 15A. If it is 14 AWG then forget about it and start over.
  • You need a single 20A breaker. You should be able to replace one of the existing double stuff breakers. You can replace the 15/15 with a 20/15 or the 15/20 with a 20/20. Do not upsize anything else at the same time - i.e., if you replace the 15/15, you can't put in a 20/20 because you have to assume that at least some of the wire on the other 15 is only 14 AWG.
  • In the panel: The black wire from the cable goes to the new breaker. The white wire goes to the neutral bar (except...GFCI, see below). The ground wire might be going to the neutral bar or the ground bar right now, or (hopefully only if this is the main panel) neutrals and grounds mixed together. But seeing what a mess you already have, anything is possible.
  • This will leave you with one unused 15A breaker, which can be used for another new circuit.

GFCI could complicate things here. Generally speaking, new receptacles in a garage (among other places) need to have GFCI protection. That can be at the panel, except not normally as part of double stuff breakers, and you are out of space to do anything except double stuff without a lot of extra work. So that means taking back the single plain receptacle and getting a GFCI receptacle (single or double) instead.

But I'd be really concerned about other problems. Knowing about problems with just one dryer circuit, who knows what else is possibly wrong. Touching "anything" in the panel could be a recipe for disaster.

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    I definitely have a lot to learn before I start rewiring the circuit breakers. But I do thank you for helping me understand all this better. I can’t believe a new condo would have such a botched electrical setup. So I guess I should be calling a professional at this point...
    – Popcorn Bad Dude
    Oct 5, 2020 at 3:57
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    Maybe "new to you". I would assume this is a relatively old building. Why? The tiny panel. Normally a tiny panel (12 spaces) is an indication of an older installation from before the need for AFCI or GFCI circuits (the two with test buttons in the lower right) and all the other things that ended up requiring all the double stuff breakers. Replacing panels is not always cheap or easy, so it is understandable to get as much as you can from an old panel. But in a new installation, a bigger panel costs very little extra. Therefore, likely old.
    – manassehkatz-Moving 2 Codidact
    Oct 5, 2020 at 4:04
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    Just saw the comment - 2008! That is awfully new for a panel this small. Makes no sense whatsoever.
    – manassehkatz-Moving 2 Codidact
    Oct 5, 2020 at 4:07
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    Something doesn't add up. I can see a developer cutting corners - save $20 by using a tiny panel, etc. But wiring up a 240V receptacle that way is absolutely crazy. Even if the developer got a cheap electrician and managed to slide through inspection, it makes no sense at all.
    – manassehkatz-Moving 2 Codidact
    Oct 5, 2020 at 4:39
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    Between the questionable judgement with the tiny panel, and the idiocy with the 30A outlet, hiring an electrician to spend a few hours auditing the homes wiring for other dangerous blunders might not be a bad idea.
    – Dan Is Fiddling By Firelight
    Oct 5, 2020 at 15:59
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Unless your appliance likes 240V, this is a very bad plan. Measure between the black and white wires when the breakers are on. Then turn them off and rip this mess out.

That's a very not remotely to code outlet. Nor is what propose doing (if this were not all the things it is) remotely to code or safe.

3-wire dryer outlets have been off the table for 20 years now.

Wiring a 240V outlet on two separate 120V breakers that are not (at minimum) handle-tied is unsafe and a code violation.

Your proposed approach of paralleling two breakers to one outlet (if you had a different starting point than you appear to) is also very much unsafe and a code violation.

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    Really appreciate the input. The Master Blaster draws 110 volts. I’m surprised at your comment about 3 wire dryer outlets being out for 20 years since the condominium I live in was only built in 2008.
    – Popcorn Bad Dude
    Oct 5, 2020 at 3:35
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    Code change was the 1996 edition. But the wiring for that outlet is a blatant violation, so it may have been a homeowner special using parts you can still buy to "maintain" your pre-1996 installation. Or else the "inspector" was simply inspecting a briefcase full of cash or drugs, not the worksite.
    – Ecnerwal
    Oct 5, 2020 at 3:40
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    Considering that it is fed by an illegal breaker configuration, and the box is a remodel box I would suspect it was never inspected. The NEC has prohibited installation of new 3 wire dryer receptacles for around 20 years, it is possible your local jurisdiction doesn't adopt the current code in a timely manner. KS and IN are currently still using the 2008 edition.
    – NoSparksPlease
    Oct 5, 2020 at 3:41
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    IF the wire is 12Ga and IF you can source a "tandem 20A" to replace your "tandem 15&20A" (or a 15& 20A to replace your 15&15) you might be able to install a 20A 120V outlet. If the wire is 14Ga you will need to pull new wire.
    – Ecnerwal
    Oct 5, 2020 at 3:45
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    Depending on state law your only recourse would likely be against seller if they indicated on the form 17 that all work performed was legally performed, but this really should have been discovered by the buyers inspection.
    – NoSparksPlease
    Oct 5, 2020 at 3:51
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Somebody probably switched the plug on the factory cord to run some 240V device - could be a welder, a table saw, etc., so they could use a 20A 120V receptacle they had on hand, then made bootleg connections in the panel. Their creative wiring made a number of code violations and safety issues.

In the panel, you can't use separate breakers for a 240V receptacle, not even with a handle tie; you need common trip, where the breakers both open on any overload.

At the outlet, you must use a receptacle made for the voltage and current of the circuit, you can't use the wrong receptacle and cobble together an adapter cable or put a new plug on your equipment.

The fix might not be too hard, re-terminate the wire for one of the 15A circuits in the panel (the white jacket indicates the NM cable is only suitable for a 15A circuit), terminate the outlet with a 15A receptacle, and the violations are corrected. However that doesn't fix anything if damage was done to the wires or connections. That's not likely since ultimately the breakers were sized to the wire. Still, it couldn't hurt to have things checked out and see if any other hazards are present.

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    See NEC 240.15(B)(2) for use of single pole breakers with handle ties on 240v circuits.
    – NoSparksPlease
    Oct 5, 2020 at 13:54
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    Your first paragraph seems to be based on confusing what the OP intended to do (install a 20A 120V receptacle) and what they actually had (a 30A 240V outdated dryer receptacle bootleg wired to two separate 15A breakers)
    – Ecnerwal
    Oct 5, 2020 at 15:37
  • "In the panel, you can't use separate breakers for a 240V receptacle, not even with a handle tie" I thought you only needed common trip when the same circuit has both 120V and 240V loads on it, and that handle ties were generally fine otherwise.
    – Joseph Sible-Reinstate Monica
    Oct 6, 2020 at 6:10
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Jacket on your Romex is white. That means 14 Guage wire, 15A max. Google "Electrician near me" because you have a maxed out panel my friend

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    @ThreePhaseEel according to this question it was 2001 when the color coding came into existence. I built my garage and updated in-house wiring in the early 90s, and both #12 & #14 NM-B came with white jackets. (Did I just correct TPE? He must have been drinking... ;) As this is ID'd as a 2008 build, the wire color comment is correct. However, it doesn't really stand as a good answer on its own according to Home Improvement standards.
    – FreeMan
    Oct 7, 2020 at 13:43
  • @FreeMan -- yeah, my memory must have failed me on that one
    – ThreePhaseEel
    Oct 7, 2020 at 23:42

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