Correct way to put a 110V (three-prong) dryer onto a 240V circuit? Or should we just throw it in and get a new one?
May 17, 2012 8:45 PM   Subscribe

We've swapped out a three-prong dryer cord with a four-prong one but not wanting to plug it in and potentially blow something up. Approach from here?

We have a Maytag 5000 Series with Steam dryer (as far as I can tell, this is the manual) and have just moved it to a new house. It had a three-prong adapter to a 120V connection at our old house but the new place has a four-prong connection (which I'm assuming, from what I've read) is 240V.

I purchased a four-prong power cord (Amazon) and swapped out the cords (using this guide) but decided to stop before plugging it in and go "hmm, this is a 120V device..."

Since then, calling and searching haven't really turned up anyone trying to do this---I have yet to find stories of people blowing out their dryers with too much voltage and similarly haven't found much about people trying to run them on different circuits with success or failure besides a couple people trying to run a 240V dryer on a 140V circuit. I found a few references to the existence of transformers for this situation but not a lot about installing them or whether that's appropriate or not.

Is there a simple way to approach this problem so that we can have laundry this week or should we just scrap it and get a new dryer?
posted by jgunsch to Home & Garden (12 answers total) 1 user marked this as a favorite
I don't think you should plug it in. Unless I'm mistaken, that guide is for converting a 240-V/2phase 3-pin (hot-hot-neutral) appliance to a 4-pin 240V2/phase outlet (hot-hot-neutral-ground). Your appliance, according to the PDF you linked, is 120V/1phase and expects hot-neutral-ground.

What does the appliance's old plug look like? Can you find it on this list of outlet types?

You might be able to convert it by ignoring one of the hot leads— this should work electrically, but may be unsafe or not-code for some reason I don't know about.
posted by hattifattener at 9:02 PM on May 17, 2012

From your Wikipedia list, new plug is NEMA 14-30 (left plug in this diagram) and old one is NEMA 10-30 (wiki picture).

I'd be curious to approach it with the "only plug in one hot lead" approach. My introductory-circuit-class-level knowledge seems to say "yes, that sounds reasonable" and the rest of my sense says "that's probably a bad idea for some reason I don't know about." Does anyone else have advice to offer on this front?

Alternately, if we were to call a technician (I imagine it'd be quite a bit cheaper to try to "fix" it one way or another), what approach would we likely want to take? Pros/cons of "install a new outlet in the house" (we're only renting, so it's not like it'd be a permanent change for us for the next decade) vs. "get the dryer tweaked with a transformer" vs. "get a new dryer"?
posted by jgunsch at 9:30 PM on May 17, 2012

Huh, the NEMA 10-30 you linked to is listed as a 240V / 2phase ungrounded plug. Maybe your dryer actually is 240V? Does it have an electrical specification plate on the back somewhere? Is there anything written or stamped by the terminals where the cord connects to the appliance, that might indicate what it's expecting?
posted by hattifattener at 9:53 PM on May 17, 2012

Something isn't making sense. The manual you linked is for a 120v gas dryer; the cord you linked is for a 240v set-up. Can you confirm via the model number what the actual requirements are?
posted by Forktine at 9:57 PM on May 17, 2012

The manual you link to is for a gas dryer, and, as hattifattener points out, both of those plugs are for 220/240V.

I think you need professional help to do the plug conversion safely, but I doubt you need a new dryer.
posted by jamjam at 10:00 PM on May 17, 2012

I'm not an electrician by any means, but according to the manual you linked (assuming that is the correct one for the dryer you have), it only expects a 120V 15- or 20-amp connection. In other words, a standard household outlet. They do recommend that it be placed on a separate circuit serving only the dryer, which is a good idea. This makes sense since it's a gas dryer: it doesn't need a ton of power for heating like an electric dryer would. You do have gas available right?

You could get an electrician to convert the four-prong 240V outlet to a normal 120V one, or you could just connect the dryer directly to a normal three-prong 120V outlet, keeping in mind that it should really be on its own circuit. The manual recommends against extension cords, and I'd really advise against long-term use of an extension cord for a dryer; that's a fire hazard waiting to happen.

I'd second hattifattener's advice to check the dryer for some kind of marking indicating exactly what its power requirements are. The NEMA 10-30 cord you say it had before is for an ungrounded 240V connection, but the manual says the dryer wants 120V grounded. The marking plate probably has the full model number of the dryer if nothing else.
posted by zachlipton at 10:04 PM on May 17, 2012

The manual should be this one.

The installation instructions are here.

The manual you link to is for only the gas version of the dryer, which only requires 120V. You have the electric version of the dryer. The electrical connection is called 120V/240V because the dryer motor is 120V and the heating elements are 240V. The three or four wire connection provides both required voltages.

If your 4-wire cord matches your outlet, then it will properly provide the both 120V/240V voltages required for your dryer. See the installation manual above.

One extremely important step is to remove the white wire on the dryer that was connected to the green ground screw on the dryer and instead connect that white wire on the dryer to the same center screw as the white wire on the cord. This connects neutral to neutral. Then connect the green wire on the cord to the green ground screw where the white wire used to be. The red and black are two legs of 120V that go to the two outside terminal screws. The two legs are each 120V and 180 degrees out of phase so that they provide 240V for the heating elements. One of the legs provides 120V for the motor.

Make sure you understand that previous paragraph. With your old 3-wire cord, there is no separate ground in the cord, so on the dryer, the little white pigtail on the dryer was connected to the green ground screw so that neutral and ground are connected together. This is no longer allowed in the electrical code. There must be a separate green ground wire. So you must remove the white wire on the dryer that was connected to the green ground screw and instead connect it to the center neutral screw.
posted by JackFlash at 10:04 PM on May 17, 2012 [3 favorites]

@JackFlash et al.: thanks, I think that likely cleared up a lot. I see now that I definitely linked to the wrong manual, and that probably caused a lot of the confusion in the above answers (and a lot of correct guesses that my assumptions were wrong)---we have a pure electric dryer, no gas involved.

Looks like we'll be going forward with double-checking the wiring and using the new plug! Thanks all.
posted by jgunsch at 10:48 PM on May 17, 2012

Most importantly, make sure you connect the green ground wire on the cord to the green ground terminal on the dryer. That is your safety ground.
posted by JackFlash at 10:57 PM on May 17, 2012

I would really call an electrician. Dealing with high voltage like that would make me nervous. Especially with something like a dryer which is the cause of a lot of house fires.
posted by majortom1981 at 4:54 AM on May 18, 2012

Since you are renting, do not throw out the old cord. I have had to exchange cords on my dryer with every move. While not a major expense to buy a new cord if needed, it is a hassle. It's so much simpler if you can just reach in the bottom of the tool box after moving all your appliances and finding that you need the three-prong cord and have the four-prong installed.
posted by Talia Devane at 6:13 AM on May 18, 2012

Do not do this on your own.

If you're asking this question, the only right answer is "get an electrician".
posted by chrisfromthelc at 9:28 AM on May 18, 2012 [1 favorite]

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