Using a range cord for a dryer
September 14, 2018 7:19 AM   Subscribe

Anyone have experience with appliance cords? Can we use an appliance cord (or range cord) with a dryer without causing safety concerns? We bought a new dryer and in the process discovered that prior owners had installed a range outlet instead of a dryer outlet. The dryer is here and has a proper 3-prong dryer cord attached but cannot be plugged in. We could either get an electrician to swap out the outlet, or buy a range/appliance cord for the dryer and continue to use the existing outlet. Anyone know enough about this to say if this is a safety hazard or just a compatibility/future convenience issue?

Some other details - We don't have a functioning dryer until we sort this out. We could get the range/appliance cord and get things working ourselves today, otherwise we're dependent on our handyman or another electrician to help with the outlet. We're not comfortable doing electric work ourselves.

In terms of technical specifications, it looks like both cords/outlets support the same voltage (240) but wattage is different (7500 for the dryer cord, 12,500 for the appliance cord) and different amperage (30 for dryer, 50 for appliance).
posted by moshimosh to Home & Garden (15 answers total)
I am not your electrician. The big question is -- are the breakers and wiring properly matched to the outlet that's there, or is the outlet dangerously promising wattage that it can't safely deliver?

If it's a true appliance circuit, then there's nothing safety related preventing you from running a dryer off it, and I wouldn't mind swapping the cord, though you should ideally swap the outlet instead.

On the other hand if the outlet promises 12KW but can only deliver 7 because of wiring or breaker limitations, then the outlet should absolutely be replaced because that's dangerous and bad.
posted by seanmpuckett at 7:32 AM on September 14, 2018 [3 favorites]

It’s been a few years since I worked installing appliances, but we always brought a range cord on our dryer deliveries for exactly this situation. Since the range cord has a higher amperage rating than the dryer cord you should be fine.
posted by doctord at 7:32 AM on September 14, 2018 [2 favorites]

@seanmpuckett - thanks for your thoughts. Any easy way for a lay-person to determine the breaker/wiring limitations? If it helps, we've been in the house for nearly 2 years and the dryer has been running fine, just getting old and we needed to replace the washer so we bought the pair.
posted by moshimosh at 7:37 AM on September 14, 2018

If it was me, I'd take the cord off the old dryer that was working for 2 years and fit it to the new one.
posted by flabdablet at 7:39 AM on September 14, 2018 [2 favorites]

You can check the breaker rating in the house electrical panel if it's properly labeled for where each circuit goes. Otherwise stuff would need to be traced which can be annoying (though you could do it yourself).

If you've been using a dryer on that circuit for a couple years, I agree, just swap the cord.
posted by seanmpuckett at 7:46 AM on September 14, 2018 [1 favorite]

Swapping the cord on a dryer to match the outlet is a totally normal thing that the dryer is designed to accommodate. There should be instructions that came with the dryer (or you can find) that explain how to do it. It’s just unbolting the old one and bolting in the new one, matching the color codes.
posted by Huffy Puffy at 7:51 AM on September 14, 2018 [2 favorites]

Also, if it was me, after the new dryer was up and running I'd book a sparky to come and upgrade the outlet to a properly earthed four prong type (30A or 50A depending on the rating of the wires in the walls) and fit a new cord to the dryer that suits the new outlet.
posted by flabdablet at 8:20 AM on September 14, 2018 [1 favorite]

The difference might not be that it is a range cord vs. dryer cord; there is a 4 prong grounded 30-amp plug that has a separate safety ground and neutral. The one used with a dryer in older houses is a 3 prong 30 amp plug without the separate safety ground. (info/pictures)

It's really easy to replace the cord as other people have said.

But if it is an actual 50 amp range outlet, that should probably be fixed eventually (unless it is actually a 50 amp circuit).
posted by ArgentCorvid at 9:55 AM on September 14, 2018

The How To Install 240V Cords video in the page ArgentCorvid linked gives me cold chills. Putting that up as any kind of model to emulate is just plain irresponsible, in my view.

The guy is really sloppy when tightening the screw for the neutral wire. Instead of holding the lug in position as he tightens down the screw, he allows the screw to twist the lug over to the extent that it looks like it would take scarcely any wiggling to make it short out on the left-hand hot lug. This happens in both the three-conductor and four-conductor demonstrations.

When he's fitting the strain relief to the flat 3-conductor cable, the cable is shoved all the way over to one side instead of being bunched up in the middle, so that instead of the clamp being allowed to screw all the way shut and grip the whole cable, one side of it pinches one of the hot wires and the other side does nothing at all.

Take your time, do it neatly, do it right.
posted by flabdablet at 11:55 AM on September 14, 2018 [2 favorites]

I have done this swap before. You need to connect the new cord up correctly, but there is a procedure for it. Find yourself a reliable set of instructions for your specific model of dryer, follow them diligently, and you will be fine.
posted by Anticipation Of A New Lover's Arrival, The at 12:50 PM on September 14, 2018

It would help if you could post pictures of both the outlet and the dryer cord just to verify what is going on. Are they both 3-prong? And can you verify that the 50-amp socket is connected to a 50-amp breaker in your electrical panel?

If the dryer outlet is 4-prong, then you need to make a change on the dryer when replacing the 3-prong cord with a 4-prong cord. You need to make sure you remove the ground strap between neutral and ground in that case and attach the ground wire to the ground terminal.

But in general, it shouldn't be a problem plugging an 30-amp dryer into a 50-amp circuit. You just need to swap the cord.
posted by JackFlash at 3:31 PM on September 14, 2018

Appliance repair professional here.

Make sure that your circuit breaker for that circuit, and the cord, are both rated for the amperage your machine asks for in its installation instructions. If you don't know what the cord is rated for- *go to the dang hardware store and get one you're sure about, they're $15.* If something is rated for even higher amperage, that's good too.

Other than that, just make sure you've got tight connections when you attach the cord to the terminals in your machine. That is; hand-tighten until it's definitely snug, and give each screw a little extra turn. You don't want a loose screw where the current can arc (spark) between an iffy connection.

Whoever installed the wrong outlet was having a real idiot moment. Proper dryer outlets/plugs have various shapes that each correspond to a rated amperage, to prevent customers from plugging in a machine that draws more amps than the breaker/cord is rated for. The cord that comes with your dryer is the correct shape for its needs, and if your outlet isn't usable, you'll have that head-scratching moment where you've been given an obstacle, for your own safety.
posted by panhopticon at 7:08 PM on September 14, 2018

Thanks everyone for your help. We are trying to switch the cord on the dryer ourselves so it’s usable while waiting for the electrician to upgrade the outlet. Would be easier if the screws put into the cord during installation weren’t so tight that we stripped them trying to get them off. It’s always something!
posted by moshimosh at 3:03 PM on September 15, 2018

I don't think this is a case where you get something to work until it can be done properly. Either it's safe to use or it isn't.
posted by bongo_x at 12:48 AM on September 16, 2018

That's true, but not terribly helpful.

Three-wire cords are safe to use if both they and the circuit they're plugged into are in good condition, but there are more ways for three-wire circuits to fail into an unsafe condition than is the case for four-wire ones.

With a three-wire outlet and cord, the metal casing of the dryer ends up connected to the neutral side of the mains supply. In theory that's fine, since in theory the neutral side of the mains is at ground potential. In practice it's pretty much at ground potential.

There are classes of electrical fault - some of them not even involving the appliance connected via the three-wire cord - that can put the neutral pole on one or more household outlets substantially far from ground potential without making it immediately obvious that any fault has occurred; in this case, the housings of appliances "earthed" to neutral will actually become to some extent live.

Four-pin 240V outlets and three-pin 120V outlets both have a dedicated ground pin, connected to an actual chunk of metal stuck into the actual ground via wiring dedicated solely to that purpose. Unlike the neutral side of the supply wiring, the only time the ground wiring carries current is when it's actively dealing with an electrical fault.

Equipment that's plugged into a grounded outlet gets its casing connected to ground via that wiring. And sure, there are still certain classes of fault that will render those casings somewhat live, but these involve both failure of the ground wiring and some other fault occurring at the same time.

So yes, either it's safe to use or it isn't; but the point is that you can't tell which of those conditions currently applies just by looking at your dryer. It's safe to use if the casing is connected to an outlet pin that's at ground potential, and the appliance is supplied from a circuit and wall outlet rated to deliver as much current as it needs.

A 30 amp dryer fitted with a properly wired three-pin 50 amp rated range cord plugged into a properly-wired 50 amp rated outlet and circuit is usually safe to use, because the neutral pole of the mains supply is usually near enough to ground potential, and plugging an appliance that draws at most 30A into a circuit capable of supplying 50 is no problem (unlike the reverse). This is why I recommended simply transplanting the old 50A three-wire cord from the old dryer to the new one.

A 30A dryer fitted with a properly wired four-pin 50A-rated range cord plugged into a compatible 50A-rated outlet and circuit also gives you dedicated earth wiring for the casing and is almost always safe to use. "Almost always" seems to me to be a worthwhile safety upgrade from "usually", and that's why I also recommended getting a sparky in to upgrade the outlet and cord to four-wire types. But there are millions of older houses in which the three-wire outlets have been considered "done properly" for decades.
posted by flabdablet at 5:47 AM on September 16, 2018

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