Is there a safe way to convert a 4 prong dryer plug to a 3 prong?
August 3, 2013 2:30 PM   Subscribe

I just bought a used dryer on Craigslist that has a 4-wire plug (14-30). My apartment has a 3-wire receptacle (10-30R). Is there a safe way to switch the plugs without an external ground?

I live in an apartment complex so outside installations are out of the question. The installation manual provides instructions for switching out the plug but stipulates in the 'Optional 3-Wire' section on page 9 that the previous steps are viable only if you follow codes. My state follows the 2011 NEC codes without alterations and, as far as I can tell, this means that it's legal for me to convert 4-wire to 3-wire because of the older model plug but it still has me a little bit worried.

Electrical engineering is a inside baseball to me but it seems that some internet commenters are worried that wiring the ground back into itself could electrify the frame. I've also read that bonding straps alleviate this problem somewhat but wouldn't this just create a pathway back into the wholly metal frame anyway?

Additionally, I called my leasing office and they apologized profusely for not knowing the rating on the plug. My dryer offers the option between a 208v/120v connection and 240v/120v connection so is it is within reason that the utility closet could provide enough power for the heating element in the dryer? Or should I just DTMFD at a recycling center and buy an older three-prong model on Craigslist? I've seen some go for >$50 and I'm guessing that's cheaper than hiring an electrician.

Snowflake: I'm somewhat poor and unemployed at the moment and I'd like to minimize the chance of accidentally electrocuting myself, my girlfriend, or our cat due to my incompetence. I'd also like to be able to pay rent for the next month ;_;

Thanks for your time!

Somewhat previously (but sort of the opposite)
posted by dubusadus to Home & Garden (14 answers total)
No, there isn't. 4-prong means it's a 220V appliance, and 3-prong is 110V. A step-up transformer will cause enough current draw to blow a fuse/trip a circuit breaker.
posted by Sintram at 2:40 PM on August 3, 2013

Your building has the newer style outlet, so I think you're better off with a newer dryer.

Sintram: I think you are confused. The 3-style plug dubusadus is talking about is 120/240/neutral with no separate ground. It is obsolete and used with older dryers and air conditioners.
posted by Pruitt-Igoe at 2:44 PM on August 3, 2013

Oops, I'm confused too. You said that the dryer is 4-prong and the outlet is 3, not the other way around.

I would get the outlet rewired. Unless your building wiring is very old (ungrounded outlets in other spots) I doubt it would be very expensive.
posted by Pruitt-Igoe at 2:53 PM on August 3, 2013

My building has the older 3-prong outlet but the dryer has the newer 4-prong plug. My understanding is that my dryer's plug is too new for the apartment. I'm guessing that means that the dryer will have enough energy to spin but not enough to heat up.

If that's the case, damn.
posted by dubusadus at 2:53 PM on August 3, 2013

No, grounding is the concern, not power or voltage.
posted by Pruitt-Igoe at 2:55 PM on August 3, 2013

Great. I'll talk to the leasing office then. Thanks, Pruitt-Igoe.
posted by dubusadus at 3:02 PM on August 3, 2013

You can switch the plug on the back of the dryer to a three prong style. Takes ten minutes with nothing more than a screwdriver. I've had to swap both ways, and I've even had an appliance repair guy cap off a wire in our code approved four prong outlet because the electrician who installed it years ago did it improperly.

Ground to the dryer frame. It won't be electrified. Every other dryer in your building is done this way. Even modern dryers often include instructions for old three prong wires.
posted by shinynewnick at 3:05 PM on August 3, 2013

When I went to buy a dryer, I just told the guys at the hardware store which kind of outlet I had - it turns out buying the plug was separate from buying the dryer, and the dryer would work with either. I would, frankly, write down what kind of dryer it is (heck, maybe even take a picture of where the cord connects in the back and the metal plate with the model information), and head down to your local hardware/appliance store, and ask the folks who work there if you can buy a 3-prong cord for your dryer. If it's a major brand, I bet you can.
posted by amelioration at 4:37 PM on August 3, 2013

As shinynewnick says, you can swap the 4-prong cord on your dryer for a 3-prong cable. 4-prong outlets were only required for construction after 1996 and the existing 3-prong outlets are grandfathered in and allowed.

Having the outlet upgraded to 4-prong is preferred but there is an expense involved in rewiring. 3-prong cords were used for over 60 years and are less safe sort of like a car without airbags and anti-lock braking system.

Most dryers provide instruction for connecting a three or four wire cable. This is standard procedure, not anything unusual. For example see here on pages 6 through 13.
posted by JackFlash at 4:37 PM on August 3, 2013

Or see these instructions at
posted by Pater Aletheias at 4:57 PM on August 3, 2013

At least in my neck of the woods, walking into any appliance or big box hardware store and asking for a three prong 'pigtail' plug for a dryer will get what you need.
posted by ndfine at 5:04 PM on August 3, 2013

Switch to the 3 prong, the same dryer can use both cords. If you want extra grounding (overkill, but cheap and easy to do) add an extra ground wire. Most dryers have a green screw on the back, run a wire (10 gauge solid single strand) from it to a nearby water pipe (not valid for plastic pipes!) and attach it with a pipe grounding clamp.
posted by 445supermag at 5:42 PM on August 3, 2013

If you want extra grounding (overkill, but cheap and easy to do) add an extra ground wire.

DO NOT DO THIS. When you make make the 3-wire connection, you also connect the chassis to the neutral. If you then also make an external connection between the chassis and some other ground, you will have made an inadvertent connection of neutral to ground outside of the breaker box. This is a violation of the code and a very bad idea.
posted by JackFlash at 6:47 PM on August 3, 2013 [7 favorites]

Update: leasing office said they weren't interested in installing a new plug so I ended up swapping the four-prong for the three-prong with no issues. Dryer ran just fine today. Thanks everyone.
posted by dubusadus at 11:53 PM on August 5, 2013

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