How to use non-standard dryer outlet?

Question

The summary:

I have a dryer that I've owned for likely a decade now. I believe it came with a three-prong cable (where the grounding is pulling double-duty on one of the three prongs.) However, in my last apartment, it had a conventional four-prong outlet and so I swapped the cable for a four-prong and installed that correctly.

I recently bought my first house - this did involve a home inspection where the inspector started a cycle on the dryer and observed the previous owner's dryer to be functional and thus powered - during this inspection, the actual outlet wasn't visually inspected; the operability of the dryer was assumed to indicate that there was a good outlet and I didn't make note of a non-standard dryer brand, cable, or adapter.

The house is a Queen Anne Victorian - this is likely not the first outlet installed for a dryer, but I do not have records of the last renovations done to this section of the house (or any sections, really)

This plug, obviously, does not fit the wall socket.

• How can I get my dryer to work? I'm suspicious that the previous owners simply stuck a conventional three-prong cable into the wall, since it looks like it would physically fit - much in the same way of sticking a conventional two-prong cable into a conventional three-prong outlet.
• How should I get the dryer to work? If the above assumption is correct, is this bad for the electrical system/dryer? Should I hire an electrician to replace this plug with a conventional one? Does this imply that I shouldn't assume a standard dryer is compatible simply offhand?
• (Optional) What's the deal with this plug? Every time I look up information online, it shows the standard four-prong arrangement and I don't have the know-how or terminology to make a better search. My hunch is that this was one of the first few "grounded dryer cables" when the idea was simply 'take a non-grounded cable type and just add a round ground wherever it fits best' instead of the specialized configuration that would become the standard, and that the time period when this occurred was too brief for casual reference on the internet.

Thanks in advance! Location is United States.

Answer 1

The easiest way to resolve it is open up the box, and see what the cable looks like coming into the box.

If it has 4 conductors (Separate neutral and ground) and the ground is bonded to the metal box like it's supposed to, then all you need to do is change the socket on the lid from NEMA 10-30 to 14-30, and wire it exactly as you found it (hot-hot-neutral). Ground will get picked up via the metal box lid's contact with the metal box, once you tighten the screws.

If it has 3 insulated conductors and metal conduit running back to the panel, then the metal conduit is equivalent to the ground wire, and see above.

If you are able to retrofit a #10 bare ground wire from the ground screw on that box to any other location with a #10 or larger wire going back to the panel (e.g. the bare copper grounding electrode wires going to the ground rods, or the water heater, or anywhere with metal conduit going back to the box... then you can do the above also.

Obviously you can run the #10 bare ground all the way back to the panel if you really want to. But any intermediate point with #10 or larger back to the panel will also suffice, and metal conduit counts as "larger" lol.