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So we got a new washing machine to go in a house built in the late 50s. When the appliance installer came to deliver the appliance, we ran into a snag with connecting the washer...the washer appears to have a standard 120 volt connector, but the plug on the wall for the washer appears to be a 240 volt/20 amp plug.

the plug

The appliance delivery didn't know what to do with the crazy outlet and thought he could just run the cord over to a standard plug 6 feet or so away (used by the sprinkler control system with extra plugs for whatever) but the cord was too short. My intuition would be that washers and dryers are usually on their own circuit for a reason, and running a heavy duty extension cord would be a bad idea.

So what do we need to do to hook this up? Is there an adapter or wiring change that would convert this plug to the voltage needed by the washer? Or do we need to exchange the washer for one designed for a 240 volt plug? Or would an extension cord actually be a reasonable solution?

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You're going to have to either get a washer that accepts 240V, or change the circuit.

New Washer

Getting a new washer will depend on the manufacturer, dealer, and other factors that are off topic here.

Change the circuit

Modifying the circuit will require knowledge of electrical safety practices, and general electrical wiring principles/standards/codes. If you lack this knowledge, or are not comfortable working with electricity, please contact a local licensed Electrician.

If you decide to tackle this project yourself, here is an overview of what needs to be done. You'll be going from a configuration with two ungrounded (hot) conductors, and one grounding conductor (NEMA 6-20). To a configuration with one ungrounded (hot) conductor, one grounded (neutral) conductor, and one grounding conductor (NEMA 5-20). To do this you'll have to swap out the double pole breaker for a single pole breaker, and repurpose one of the conductors.

At the Panel

  1. Before you begin, you'll need to purchase a 20A single pole circuit breaker that is compatible with your service panel, and a blank panel cover insert.
  2. Start by turning the power off by flipping the main breaker to the OFF position, then verifying that power is off using a non-contact voltage tester.
  3. Remove the service panel cover (be careful working in the open panel, the main lugs are still energized even when the main breaker is in the OFF position).
  4. Locate the breaker for the washer.
  5. Remove the wires connected to the breaker (should be either black & red, or black & white).
  6. Remove the breaker from the panel.
  7. Install the new single pole breaker in one of the slots where the old double pole breaker was.
  8. Install the blank panel cover insert in the panel cover, so that is covers the empty space left.
  9. Connect the black wire that you removed from the breaker in step 5, to the new breaker.
  10. If the other wire from step 5 is white, connect it to the grounded (neutral) bus bar. If the wire is red, mark the wire with a bit of white tape, or a white marker, then attach it to the bus bar.
  11. Reinstall the panel cover.

At the receptacle

  1. Before you begin, you'll have to purchase a 125V 20A receptacle.
  2. Uninstall the old receptacle.
  3. Connect the black wire to the brass screw terminal on the new receptacle.
  4. If the other wire is white, attach it to the silver screw terminal on the new receptacle. If the other wire is red, mark it with white tape or a white marker, and attach it to the silver screw terminal on the new receptacle.
  5. Attach the bare or green grounding wire to the green grounding screw on the new receptacle.
  6. Mount the receptacle in the box, and install the cover plate.

Once everything is finished, you can flip the main breaker, and the new breaker to the ON position.

WARNING:
This answer is only applicable in the US, and possibly Canada.

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  • Are multi wire branch outlets no longer code, where one side would be the black "split" and the other the red "split", both sharing the neutral? More problematic would be the lack of a ground. Going to 2 20A GFCI (with no equipment grounds) would seems to solve that.
    – HerrBag
    Jun 18, 2013 at 19:31
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    whatcha talkin bout @HerrBag? There is no grounded (neutral) conductor connected to a NEMA 6-20R, it's straight 240V. It's ungrounded (hot), ungrounded (hot), equipment ground. Which can be rejiggered (if you know what you're doing) to NEMA 5-20R, which is ungrounded (hot), grounded (neutral), equipment ground.
    – Tester101
    Jun 18, 2013 at 20:06
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    Great answer, but I would add, after turning off the main, double check the wires going into the breakers with a non-contact tester to make sure they are actually off. Yes, I know cutting the main cuts all the circuits, but someone unfamilar with the system just might have turned off a branch thinking it was the main.
    – bib
    Jun 18, 2013 at 21:00
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    @HerrBag from the same wiki "All NEMA 6 devices are three-wire grounding devices (hot-hot-ground) used for 208 V and 240 V circuits and rated for 250 V maximum". Split phase is 120/240V, that's 240V line to line, and 120V line to neutral. Three phase wye is 120/208V, that's 208V line to line, and 120V line to neutral. This is why the NEMA 6 can be either 240V or 208V, but it's always line to line with no neutral.
    – Tester101
    Jun 19, 2013 at 12:08
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    @HerrBag Your recollection is correct. You're just thinking of NEMA 10 (hot hot neutral) not NEMA 6. NEMA 10 was the split-phase counterpart of NEMA 1 (2-prong). When NEMA 1 was outlawed and grounds were made mandatory, the appliance industry feared it would stop appliance sales if NEMA 10 were outlawed, so they wangled an exception to allow misuse of NEMA 10's neutral as ground. You probably saw a lot of that, it was and still is very common. Fortunately recent law allows retrofit of ground wires alone, so it's easier than ever to fix.
    – Harper - Reinstate Monica
    Feb 6, 2017 at 23:24
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You have two concerns - the voltage differential and cord reach. On the second one - do not use an extension cord. You're in an area that could potentially become (very) wet. Mixing extension cords in there is just bad juju. On the voltage differential, you may be stuck. First, I would measure the voltage at the outlet - if it's actually 120V, you're in luck and can just change out the power cord on the washer. If it's 220V, you may need to have an electrician come in and change the circuit, if the washer can't be made to accept 220V. The general rule is to "make the device (the washer in this case) match the house", so you may also want to consult with the store that you bought the washer from.

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    If the wall voltage is 120, you should change the outlet, not the power cord. The unique configurations are meant to reflect the actual voltage so no mismatching can occur (which can ruin appliances and pose dangers).
    – bib
    Jun 18, 2013 at 17:54
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    NEMA 6-20 socket for 208/220V. If it's wired for 120V, that's a serious mismatch.
    – Fiasco Labs
    Jun 18, 2013 at 19:20

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