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I need to wire a 240v outlet in my garage for a table saw, there’s only one open space on our box so I was wanting to use an existing 240v breaker, (I guess another question is are double pole breakers 240v? Or do they have to be in two separate columns in the breaker box?)

The dryer uses 25amps.

My saw uses 13amps, right now I have a 40amp double pole for the dryer, is it safe to run the dryer and saw off that breaker? Or should I get a bigger one or maybe should I do separate?

Also, if I do put a junction box on that dryer line and run a separate line to garage, what gauge wire should I use? Normally for that size breaker you would use a higher gauge but does that change if your only needing 13amps? The garage is maybe 20-25 ft. From my panel.


It’s a square D 200amp panel. Based on the responses on here I’m thinking of adding a subpanel for the saw and dryer and another line I want to run to my shop, the dryer should probably be on a 30amp so I was thinking if I had a 60amp subpanel added I could then run new lines for both off that,

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  • Depending on your country and building code you may need a pony panel in your garage. Furthermore, you'll need a license electrician for the connection to the breaker panel.
    – Louis
    Jan 24, 2022 at 3:06
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    Yes, a double breaker is 240V. Any wiring, receptacles etc. connected to a 40 amp breaker must be rated for 40 amps. You need to add a 15 or 20 amp, 240 volt breaker. You may need a building permit. If this in in the USA, the State or local codes determine the requirements. All such codes are based on NEC, but add regulations about permits, inspections etc. Some add or delete details and may not immediately adopt the latest editing as soon as it is released.
    – Charles Cowie
    Jan 24, 2022 at 3:18
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    Can you post photos of the existing panel, including the label on the inside of the door please? Jan 24, 2022 at 12:33
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    2 people in the same day that have "unusual" breaker sizes for their dryer? Virtually all North American residential dryers are sized for #10 wire and a 30A breaker. A company that tried to sell a 40A-breaker dryer would get 2/3 of them returned by angry customers. Jan 24, 2022 at 20:41
  • @Harper-ReinstateMonica I find it curious that so many people have 40 amp breakers on their dryers because when I had my breaker panel replaced it appeared that there were no 40 amp breakers in the entire county, they are just not that common. At least that's what I picked up on by overhearing the electrician speak with suppliers on the phone. I'm seeing new "ventless" dryers on the market rated for 16 amps that come with a 30 amp cord, certainly because it allows for not needing to modify existing wiring most people have. I'd expect 40 amp dryers to be rare, as in build to order rare.
    – MacGuffin
    Jan 24, 2022 at 21:33

2 Answers 2

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You can have any number of 30A receptacles on a 30A circuit.

As long as they don't serve certain loads for which dedicated circuits are required (EVSE's come to mind). "Dryer" is not on that list.

Unfortunately, you own one of the two residential dryers in North America that take larger than a 30A circuit. I doubt that; Occam's razor suggests it's really manufactured for 30A breaker/10 AWG Cu wiring, however, you were preceded by a "nitwit" who liked to oversize breakers.

I suspect that consulting the dryer's nameplate, and its installation instructions (find model number; use Web) will affirm it's made for a 30A circuit.

If that's all true, please - correct the breaker, particularly if the wiring is only #10.

First, correct the dryer circuit to a full 4 wires.

Unfortunately a lot of dryer circuits were installed 3-wire, with a 3-prong plug. "what's wrong with that?" Dryers use 240V but they also use 120V - so they need 2 hot wires and a neutral. But you want ground, and you need it for a circuit extension.

From 1966 to 1996 they allowed 3-wire dryers and ranges, mainly to soak up existing stocks of wire that was otherwise illegal. That included /3 NM (black, white, red, no-ground) and SE cable (black, black, mesh neutral). Once those stocks exhausted they were to use /3 w/ground. Unfortunately some used /2 w/ground (abusing ground as neutral, which it isn't insulated for); that was never legal and must be removed on sight.

If the installation was legal, you can retrofit an actual ground.

Converting the dryer to 4-wire is trivial: google the instructions and they will show what to do.

Here's where I'm fuzzy on Code: Can you extend a circuit with a retrofit ground? I argue "yes". If not, change the dryer circuit to 10/3 w/ground.

Then you can extend the dryer circuit to another 30A receptacle. It doesn't need to use neutral, so a NEMA 6-30 socket can be used. A NEMA 10-30 can never be used; all NEMA 10 sockets should be smashed to prevent re-use.

Down the rabbit hole of NEC Article 430 - motors.

The saw is a motor load, but there isn't a separate article carved out for it (as there is for air conditioners, 440). This section gets pretty weird.

You didn't give us the nameplate data, so it's impossible to do a proper analysis. But most likely:

  • You need to derate by 125%, so "13A" becomes 16.25A and you must put it on a 20A circuit not a 15A circuit.
  • Notwithstanding nameplate data, You are probably allowed to go to a larger breaker to prevent nuisance trips, within certain limits. 30A is most likely within that limit.

So if you were hardwiring it dedicated, fair chance you could wire this with #12 on a 30A breaker. Really.

However, since you'll be plugging it in, that doesn't really work. You could plug in anything which means 240.4(D) kicks in, requiring #10 wire on 30A breakers. Which requires 30A sockets. 210.21. And multiple sockets allowed on 30A. 240.something.

So yeah. Extending the dryer circuit is probably legit.

Has the red queen lost her head?

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Bottom line without seeing actual installation from both appliances is you need a separate circuit for the dryer fed by a 2-pole/handle tied breaker, fed from two adjacent spaces in your panel. Your saw also needs to be fed separate from the dryer by a two-pole/handle tied breaker, and if plug connected could share with other receptacles of similar configuration, but not with the dryer.

To be NEC compliant you have to install appliances as instructed in the Installation Instructions. The Installation Instructions are part of the (UL/CSA/ETL) Listing which only certifies any appliance when used as tested and approved.

These instruction override general NEC rules about 125% ratings or 250% for motors, maximum ampacity for cord connected devices, sizes and numbers of receptacles on branch circuits.

The installation instructions for your dryer are probably quite similar to my 28A Whirlpool dryer which says (italics mine):

To supply the required 3 or 4 wire, single phase, 120/240-volt, 60-Hz., AC only electrical supply (or 3 or 4 wire,120/208-volt electrical supply, if specified on the serial/rating plate) on a separate 30-amp circuit, fused on both sides of the line. Connect to an individual branch circuit. Do not have a fuse in the neutral or grounding circuit.

Your 40A breaker is likely too big for your dryer and not providing a safe limit of current for the dryer. A 40A breaker will typically hold 110%, so that's an extra 19A over nameplate, 19A@240v means 4500 watts extra watts of heat and not trip the breaker! Current always produces heat. 4500 watts is a lot of extra heat.

Your saw probably has similar wording, or comes with a plug that fits a specific configuration receptacle. That specific configuration of receptacle will indicate the allowable overcurrent protection allowed by Code. For a 13A saw that circuit would likely would not exceed 20A, but again the specific Instructions that come with the saw need to be followed.

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  • I think you are in MO, which seems too allow local inspection authorities to adopt updates to the NEC rather randomly. The 2020 edition of the NEC would require Ground-fault protection in garages for both of these circuits if fed by receptacles. Jan 24, 2022 at 17:01

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