Is the internet wrong about dryer outlets?
January 26, 2017 7:57 AM   Subscribe

Our (new to us) dryer has no heat. The (newly installed) 4-prong dryer outlet in our rental is measuring ~0VAC across the two hot lines, but 120V between each of the hots and the ground/neutral. The contractor/electrician has insisted this is normal, but everything I'm seeing online says the voltage between the 2 hot lines should measure 240VAC. Background and what-now questions follow.

When we moved into our rental home about 8 months ago, the electrician/contractor had installed a range outlet where the dryer outlet needed to be. No big deal, we weren't planning on getting a washer and dryer soon anyway.

Fast forward to a week ago, when we picked up a hand-me-down washer and dryer from family, who had tested everything before they were shipped. The electrician came over and rewired the outlet to be a 4-prong dryer outlet. Great! But when we started using the dryer, it wasn't heating up.

I checked the newly-installed dryer outlet and it's measuring 120V from the hots to the neutral/ground points, but hot-to-hot is 0V. Everything on the internet says that this should be 240V. I've mentioned this to the electrician, who has insisted that because we're getting 120 to ground from each hot, it's actually 240 and the outlet is fine and he's done this dozens of times.

By showing him youtube videos of people measuring 240 across the hots on a voltmeter, I finally persuaded him to call his electrician buddy for verification (he'll get back to me today). I don't really trust this either, as this buddy was apparently the guy who taught him everything he knows about electrical work.

I'll do a check of the heating element for due diligence, but at this point I'm practically convinced the outlet isn't wired right, so I'm not sure what to do if the guy's buddy comes back saying the same thing.

I think my next steps would be to tell the landlord I'll have an independent electrician check the circuit. I'll eat the cost if they says the outlet's okay, but insist the outlet get fixed at the landlord's cost otherwise, whether by using our current electrician or someone new.

Am I wrong? Might the outlet actually be working this way and I should trust these guys? Is there something about older wiring that might be contradicting everything I'm reading? Would a request for third-party verification be unreasonable at this point? I'm worried I'm missing something and starting to make a fuss about a non-issue.
posted by enigmango to Home & Garden (14 answers total)
You are correct. In a NEMA 14-30R receptacle the voltage measured from both hots to ground/neutral should be be 120V but 240V when measured from hot to hot. That receptacle should be wired such that each hot is 120V but 180° out of phase, resulting in a 240V when measured from hot to hot. Most likely the cause of the problem is that the two hots are connected to the same phase on the circuit panel.
posted by RichardP at 8:07 AM on January 26, 2017 [10 favorites]

I'm not an electrician but when I purchased a house from HUD built 1917 there was a dryer hooked up to an outlet, spinning but no heat working, same with the electric stove. Turns out there wasn't a 240 line going to the house. My contractor said the only way to get it to 240V is to have a 240 line put in. If I could have gotten around it I would have, but on the other hand a working 240 is a minimum luxery, think of resale too. Maybe your 240 line into the house is malfunctioning? But maybe there's an alternative when a 240 is absent.
posted by waving at 8:08 AM on January 26, 2017

I agree with richardp, they're on the same phase.
posted by H21 at 8:13 AM on January 26, 2017

Also, If your dryer circuit was installed by a less-than-professional electrician, you may have the wrong breaker in your panel. Make sure your dryer circuit is protected by a double-pole 30A breaker (some jurisdictions also allow two single-pole breakers each rated for 30A and connected by a handle tie).
posted by RichardP at 8:20 AM on January 26, 2017 [3 favorites]

Yeah, if someone used two single-pole breakers, one for each of those 120volt legs, it's easy to get them set up wrong in the breaker box so that they're both pulling off the same phase. Totally not the way to do it, but that doesn't mean someone didn't do it that way.
posted by BillMcMurdo at 8:38 AM on January 26, 2017

By showing him youtube videos of people measuring 240 across the hots on a voltmeter, I finally persuaded him to call his electrician buddy for verification

Don't let this guy wire anything else.
posted by jon1270 at 8:40 AM on January 26, 2017 [21 favorites]

See this link.
posted by JayRwv at 9:07 AM on January 26, 2017

(he'll get back to me today)

You should get back to him first to let him know you will no longer be needing his services.
posted by humboldt32 at 9:07 AM on January 26, 2017 [1 favorite]

Yeah, if he doesn't know how 240V outlets work, this guy is not an electrician. The other guy very well may be, and is who you should be dealing with (well, or an actual electrician of your choosing) going forward.
posted by Huffy Puffy at 9:12 AM on January 26, 2017

Update - apparently his buddy does know his stuff, and we've got heat in the dryer now. He was indeed connecting the two hots to the same line. As others have noted, I'll be pushing the landlord to use an actual electrician for any future work.
posted by enigmango at 10:19 AM on January 26, 2017 [3 favorites]

Perhaps because my FIL was an IBEW electrician, this trade is #1 on my list of "things that people think they can just figure out, with catastrophic results."

Marketing is still a close second for me.
posted by randomkeystrike at 10:50 AM on January 26, 2017 [2 favorites]

In many if not most jurisdictions, rental properties are required to have work done by licensed trades, and most likely permitted/inspected.
posted by werkzeuger at 6:13 PM on January 26, 2017 [1 favorite]

Err... if it is a rental property the codes require a licensed electrician. Not some guy who helped watch one once. Your landlord is foolish thinking they are saving money doing this.. unless they've got the place over-insured for fire.
posted by rudd135 at 6:16 PM on January 26, 2017 [2 favorites]

I think it is likely dangerous and almost certainly not up to code to run a 240 V circuit off of two single pole breakers unless the two breakers are connected with a handle tie. I am guessing, based on your narrative, that the two breakers are not connected with a handle tie.

I'm not saying your house is necessarily going to burn down or you are necessarily going to get electrocuted because someone miswired a dryer outlet, but I would be pretty nervous living in a place where electrical work had been done by someone who doesn't understand the residential split-phase concept.
posted by Juffo-Wup at 7:57 PM on January 26, 2017

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