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I have a dryer with a 3-wire power cord. One wire was fastened to a copper water line. I replaced the copper water line with pex tubing and now the dryer won't work.

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    Looks like an open neutral and ground was taking it's place, which you lost when you removed copper pipes. Can you take a picture of your outlet, how it's wired ? – JACK Dec 15 '19 at 16:41
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    Yes, can we have a photo of the inside of the receptacle box please? Also, does the wire that was going to the pipe go to the receptacle box, or somewhere else? – ThreePhaseEel Dec 15 '19 at 18:15
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    Yes it was open neutral had a professional come run new wire to breaker box. Thank you so much for all the insight!!!! Dryer working!!!!! – Randall R Andrews Dec 16 '19 at 17:11
  • @RandallRAndrews, thanks for the update! This question needs more upvotes. Great to see a safe resolution. – JPhi1618 Dec 17 '19 at 17:07
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Danger!

A 3-wire dryer connection has two hots & neutral. It does not have a separate ground.

A 4-wire (required for all new installations for many years now) has two hots, neutral and ground.

The only time you should have a wire connected to copper pipe (and even then, it is limited for various reasons) is ground. Never neutral. So you appear to have two problems combined:

  • Neutral from dryer treated as ground by connecting to copper water pipe
  • Pex doesn't conduct so it is not a valid ground path

A typical US residential clothes dryer uses neutral for controls & lights, possibly the motor. It does not use it for the main power draw - the heating element. As a result, it can "kind of squeak by" but in a dangerous way if instead of ground on neutral (the usual 3-wire way, now deprecated) you have neutral on ground. When you made the ground no longer work (because pex doesn't conduct), instead of just losing ground (a safety issue) you also lost neutral (a functional issue).

In a way, this is a blessing in disguise, because you have found a major safety issue before it had the chance to kill anyone (seriously!).

Get this Fixed Properly

  • Replace the 3-wire cord from the dryer with a 4-wire cord
  • Remove the jumper wire in the dryer that connects ground & neutral (if you can't figure out how to do that, post the model # and we can probably figure it out)
  • Replace the 3-wire receptacle with a 4-wire NEMA 14-30: enter image description here
  • The hard part: RUN A NEW 4-WIRE (2 HOT, 1 NEUTRAL, 1 GROUND) CABLE to your electrical panel. Normally this will be 10 AWG for 30 Amp. The problem is that based on what was previously done - routing neutral as ground - it is really not clear what you will find when you get to the electrical panel. I recommend posting a picture of the electrical panel showing the current dryer circuit breaker before doing any work so that we can review it for other possible issues.

In some cases if running a new cable is not a simple thing to do (e.g., different part of the house) there are ways to run ground separately through another path. However, that is dependent on ground being the only problem. In this case, all indications are that you only have 2 wires - not 3 - going back to the electrical panel, in which case taking care of ground through an alternate method will not solve the problem.

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Pop the covers and see what you have

We're interested in what's happening at both ends of the dryer cable: The service panel end (maybe the neutral wire got corroded), and the receptacle end (maybe the wire has an issue). We need to salvage all 3 of the following wires:

  • Hot L1 (typically black)
  • Neutral (white or gray by law; except for SE cable (bare wire woven around 2 hots).
  • Hot L2 (typically red or black; yes, both can be black; white only if SE cable).

And we want to see 120V between neutral and L, and 240V between L1 and L2. Somewhat lesser voltage won't do; that is phantom voltage. 117V is within normal tolerance, 109V is not OK and is just phantom voltage.

What if my neutral is bare?

If it's a solid or stranded wire, that's no good. That's a ground wire. You cannot use that as a neutral.

However, if the bare wire is a bunch of strands woven around the two other conductors (often black and white), that is SE cable, and you get to exploit a statutory exception where you get to use the bare strands as a neutral, but then, not ground:

  • Mark any white wire with black tape (it's a hot).
  • Gather the woven wires and insulate thoroughly; it must not touch ground!
  • Do the same in your service panel. Watch for someone letting the cable clamp touch the bare wires; insulate that.

If you don't have the right voltages

Then you look closely at the wires in the panel to see if you see any damage. If you do, try to repair it. Then you follow the cable to the extent practicable from the panel toward the outlet, looking for any physical damage.

If you find physical damage at the outlet, you can try tracing the cable back toward the panel, and look for another place to put an outlet that is along the cable. You would need to fit an junction box here, assuring at least 7" of spare length of good cable inside the box. I recommend using a steel, 4" square deep junction box, either embedded up against a joist, or just surface mounted. (rather than the bakelite style recep you have now; which is unfit for the ground retrofit we'll probably do).

If all that fails, the cable is done for. You will need to pull a new 10/3 cable from the service panel to this location.

Anyway, if you're sitting there happy-dappy with two colored wires and a white wire with all the right voltages, now we go on to phase 2.

Phase 2: Making it live/safe

In all cases, you'll be hooking up a NEMA 14-30R receptacle. You'll be jumpering the dryer for a 4-wire plug, with the neutral-ground interconnect removed. If you have 4 wires that all work -- hot, hot, neutral and separate ground (I assume you had to pull a new cable), then you're at the end! Victory!

All other options assume you have 3 wires: 2 hots and a neutral.

Option 1: GFCI

Here, we fit a 2-pole GFCI breaker ($90) to replace the dryer breaker. We label the NEMA 14-30 receptacle "GFCI Protected. No Equipment Ground." And we're done.

Failure mode here is if you touch the washer-dryer chassis at the same time, you get lethal shock for about 3 milliseconds, the GFCI trips, and you don't die.

The downside of this method is that if your appliance develops a ground fault, it will keep tripping the breaker. This is the safety device actually working, so it's hard to complain about that. But it won't happen with a proper 4-wire connection, nor with an old 3-wire connection (though the latter might murder you).

Option 2: Retrofit a ground wire

NEC 2014 liberalized -- actually I think earlier NECs permitted this. You can keep the hot-hot-neutral you already have, and retrofit the ground wire. This can follow any viable route back to the panel. It doesn't actually have to go all the way back to the panel, if it can find any of:

  • A junction box that is grounded and whose wires have a large enough ground wire (we're talking 10 AWG) back to that same panel. You can't steal this from common receptacle circuits which have #12 or #14 wire.
  • A junction box with continuous metal conduit back to that panel; nonflexible or AC allowed; other flexible types not allowed.
  • Any part of the Grounding Electrode System - the bare copper wires going out to water pipes or grounding rods.
    • You are not allowed to use a random water pipe for ground. One guess why.

Option 3: Pull a new 10/3 NM or UF cable

the entire route from the panel to the dryer outlet.

Go over the rest of the house with a fine tooth comb

The last electrician was obviously a horrible shortcut-taker. This thing was practically a booby-trap, with the installer clearly oblivious to the lethality of a neutral failure in a 3-wire dryer connection. Take it to the bank that the house is full of other booby traps.

Therefore I recommend to you what I usually recommend to the over-ambitious: Make yourself a wiring expert. Have your new favorite thing be getting a book from the library on home wiring and devouring it cover to cover. Get 5000 rep here. Make yourself a subject expert on home wiring. Then go through and inspect every single box in your house.

Noting the 2-prong outlet below, this would also be a great time to avail yourself of the 2014 code and retrofit grounds!

I had the occasion to do this when we acquired a factory building for pennies on the dollar. Oh man -- MWBCs with 3 hot wires on them (no, not 3-phase panels), fan and furnace circuits stealing neutrals from other circuits in different services, therefore returning current via the building frame... it was uggggggly. Also, made me learn about (and concede the usefulness of) multi-wire branch circuits - I thought they were more wiring incompetence at first.

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