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My wife purchased a kiln that requires a 30 amp breaker, has NEMA 5-20 plug. We are going to put it in the shed but the price to run electric to the shed is not affordable.

Can I use the 240v outlet for my dryer to run a NEMA L6-30P extension cord with a 30Amp L5-30P to 15/20Amp NEMA adapter to the shed?

kiln - http://www.clay-king.com/kilns/skutt_kilns/skutt_km_614_3.html

extension - https://www.amazon.com/gp/product/B07K7X7W61/ref=ox_sc_act_title_2?smid=A15AM8MHT45F3Q&psc=1

adapter - https://www.amazon.com/gp/product/B002MGJ2F4/ref=crt_ewc_title_dp_3?ie=UTF8&psc=1&smid=ATVPDKIKX0DER

Thank you.


FOLLOW UP QUESITON:

Thank you all for your time. Very much appreciate it.

It does appear there is no ground wire, however, there is a outlet right next to it that does have a ground wire. Can it be utilized?

enter image description here


UPDATE:

I think there is a ground wire hiding under the black..

enter image description here

  • 1
    Is it a 3 prong or 4 prong cord for the dryer plug? If it's 3, then you don't have an actual ground wire there. That extension cord you show doesn't fit into a dryer plug. That's for an RV "shore power" box. – JPhi1618 Aug 26 at 19:23
  • 1
    Please edit your question to add information, or add a comment. Answers are only for answers. This is a Q&A format, not a discussion forum format. If you prefer the latter you can try diychatroom or reddit, but forums tend to be VERY noisy with the correct answer splayed across 4 posts and buried among 45 other posts, many of which are wrong. – Harper - Reinstate Monica Aug 26 at 19:40
  • Also, repeatedly guessing at products and posting their links and asking for confirmation... Is a highly ineffective way to do this. You should tell us what you have (you haven't yet!) and then listen to what we tell you. – Harper - Reinstate Monica Aug 26 at 19:41
  • Hello, and welcome to Home Improvement. It looks like you now have two separate accounts; you should request that they be merged. And, please take our tour so you'll know how best to contribute here. – Daniel Griscom Aug 27 at 1:47
3

No. Just no.

  • Current

Your kiln specs are for 20A. Your dryer breaker is (or should be) 30A. 30A is a lot more than 20A. If you had a failure where the kiln pulled 30A for a while, the breaker would not trip and your kiln might be damaged...or start a fire.

  • Ground/Neutral

Your kiln needs hot, neutral and ground. A 6-30 is a 3-wire connection. It will likely have hot, hot, ground, in which case you don't have a neutral and would then be piggybacking neutral for your 5-20 on ground, which is not to code and not safe.

Your dryer receptacle is actually more likely a 10-30, which is an obsolete-but-grandfathered type with hot, hot, neutral, in which case you don't have a ground and would then be piggybacking neutral for your 5-20 on ground, which is not to code and not safe. It is considered "safe enough" for dryers but your kiln does not fall under that limited exemption.

Your best bet to avoid running a new cable from the panel to the garage would be to see if you can retrofit ground. There are rules for doing that, but if you can legally do it then you could:

  • Replace the 10-30 with a 5-20 (no dryer any more) and replace the 30A breaker with a 20A breaker.
  • Install a subpanel. Not sure if you can use retrofit ground for a subpanel though - Harper or one of the other pros can answer that (and fill in 100 other details I missed). Then connect a 14-30 (replacing the 10-30) for the dryer, a 5-20 (for the kiln) and other circuits as well. As long as you don't run the dryer and kiln at the same time, this would probably work quite well.

Double-check the specs - and safety - of the kiln

The specs are a bit confusing:

  • 120V
  • 20A
  • 2,300W
  • 5,940 BTU
  • 10 AWG
  • NEMA 5-20

20A specifications: 20A (obviously), 5-20, 5,940 BTU (1 kWh = 3,412 BTU, so 5,940 BTU = 1.74 kWh = 14.5A @ 120V, which fits just fine on a 20A circuit)

30A specifications: 10 AWG (it is perfectly fine to use 10 for 20A circuits, but code normally only requires 12), 2,300W (2,300W/120V = 19A and since this is continuous usage it needs a circuit rated for higher current - and the next typical size is 30A)

Just doesn't add up... That could be laziness, specs not up-to-date, etc. Or it could be a sign of poor and possibly unsafe design.

  • If you click the link to the kiln, the manufacturer actually lists it for use on a 20A 120v outlet protected by a 30A breaker. I guess this means they expect that to run on 12ga wire, but OP would have at least #10 for a dryer. The marketing looks like they think they have some "special" exception to run it on a 30A breaker. – JPhi1618 Aug 26 at 19:52
  • It is all messed up, I think. Adding more notes...hang on. – manassehkatz-Reinstate Monica Aug 26 at 19:53
  • ...only electric kiln in the KM series that can be fired on common household 115C current using a special 30 Amp outlet. Yea, this is weird. They say "common household", but then say it needs a 10ga, 30A 120v circuit which doesn't really exist outside of some specialty circuits. Sounds like they want you to pull out a dryer outlet and install a 5-20, but that's just not how things work. – JPhi1618 Aug 26 at 20:04
  • But if they want you to pull out a dryer outlet, why not just use the dryer outlet and run it at 240V. – manassehkatz-Reinstate Monica Aug 26 at 20:06
3

This is kind of a "code mess" because this kiln manufacturer is good at making kilns, not so good at complying with NEC/UL rules, especially in 120V/16-20A current draw. As such, they unable to achieve UL/CSA listings in the US.

The hangups are twofold: first the device needs a 30A plug, and these are highly uncommon in US homes. And second, your dryer receptacle needs to provide both neutral and ground - and if it's a 3-prong Halloween outlet, it does not have that (possibly because the ground wire isn't there). Let's solve each, one at a time.

Plug

Your device draws 19A actual, and you need to provision power for 125% of that since it could run continuously. Therefore you are talking 23.75 amps, too much for a 20A circuit obviously, and you need to upsize to a 30A plug, socket, wiring and circuit breaker. This makes it a good fit for that dryer breaker and wiring.

That means you need to use a NEMA 5-30, or a NEMA L5-30, or the odd TT30 (intended for small travel trailers).

However, since you want to co-use this socket for your dryer, I suggest simply fitting a NEMA 14-30 plug. This is a 30A 120/240 hot-hot-neutral-ground plug, which is overkill for your needs, but will fit your dryer outlet. Quite soon.

Socket

This may get a little convoluted, depending on the age of your wiring.

If your dryer outlet is already a 4-prong NEMA 14-30, then you're done. Congrats!

Get a NEMA 14-30 dryer cord for your dryer. Install it according to the dryer's instructions. This will include a step to remove the bonding between neutral and ground. Very important, or it will defeat the safety protection we're about to add!

Now, pop off your obsolete NEMA 10-30 dryer receptacle and see the wiring behind. If a ground wire is present (but not hooked up), then install a NEMA 14-30 receptacle. You're done. Congrats!

If you don't have a ground wire, but can confirm the conductor wires run inside a metal conduit from the dryer all the way back to the panel, then look in the back of the junction box for a hole a bit smaller than the rest. It will take a #10-32 ground screw, and they sell green ones 10 for $1. Attach a 10 AWG ground pigtail to that, then install a 14-30 receptacle using that pigtail and the 3 conductors. You are done!

If you have the physical access to physically retrofit a 10 AWG bare ground wire between the dryer receptacle and the service panel, then definitely do that. Use that ground wire on a NEMA 14-30 receptacle and you are done.

If none of those are possible... Replace the dryer's circuit breaker with a 30A 2-pole GFCI circuit breaker. Make sure this is possible before continuing. Once that is done, install the NEMA 14-30 receptacle with nothing connected to the ground screw. Then, stick two labels on the receptacle (these come with the GFCI): "GFCI Protected" and "No Equipment Ground".

At this point you're all set for using that receptacle for both dryer and kiln.

Frequent use: Second receptacle

These large receptacles are not made for frequent use. This can break them. If you need to do this often, then get a "junction box expander" for the physical space, and splice on a circuit extension to go to a second receptacle. That way the dryer can stay plugged in all the time.

Since it is a separate receptacle, it can be any 30A rated type - NEMA 14-30, NEMA L14-30 (locking) or TT30. It does not need to be located right next to the dryer.

Yes, it's legal to have two receptacles on a 30A circuit. In recent years we researched the heck out of this, because most people here didn't believe it.

Big extension cords - avoid

There are three huge problems with big extension cords. First, if you get a long cord, you will be tempted to leave most of it coiled up. The extension cord will melt and catch fire if you do this.

Second, long extension cords are vulnerable to voltage drop, especially when you chintz out on them. For instance you are proposing 20A extension cords and your need to provision 24A, so you're running at hard thermal limits (worsening the "coiling" problem) and will experience voltage drop as high as 5%. That will reduce performance of the kiln.

Third, long extension cords are frickin expensive. The ones you linked are $2 to $2.50 a foot. Building hard-wiring is cheaper and higher quality by far.

"Hard-wiring" can include a pendant connection, which is stopping at a junction box then splicing to 10 AWG cordage with proper strain relief. The cordage can be any length, then end in the appropriate inline socket. The cordage must be 10 AWG, but if the socket is 3-conductor, the cordage can be too.

  • There is a NEMA 5-30, and I'd recommend it for this application over the TT-30 – ThreePhaseEel Aug 27 at 1:54
  • I have never been able to find anything like that @ThreePhaseEel but apparently my local stores stock some of them. Edited. – Harper - Reinstate Monica Aug 27 at 3:42

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