Electrical – Code requirements for moving 3 prong dryer outlet

dryerelectrical

I've read various posts here about the advantages of 4-prong over 3-prong, such as the dryer cabinet can become hot if there is an interrupt in the 3-prong neutral/ground. Examples:

Dryer Outlet – 4 prong to 3 prong

Converting a Samsung Dryer from a 4-prong cord to a 3-prong cord?

In the our utility closet/room of our house, I will be moving our 3-prong dryer receptacle that is on a non-GFCI 30amp breaker. It supplies our 2007-ish 3 prong problem-free dryer. Printed installation instructions: "Materials you will need … dryer power cord kit (not provided with dryer) UL rated 120/240V, 30A with 3 or 4 prongs. Identify the plug type as per the house receptacle before purchasing line cord". It also contains: "NOTE: Since January 1, 1996, The National Electric Code requires that new construction utilize a 4 wire connection to an electric dryer." And it gives details for 3 wire and 4 wire connections with specifics on the OEM ground strap. It also says that a 4 wire connection "must be used for mobile home installation", which is not our situation.

Relocation plans are to use a junction box at the current location, then run 4-12 feet (depending on route) to a reinstall of the old receptacle. What are the minimum code requirements in terms of 3-prong versus 4-prong?

Specifically, can I just extend as described, or … does code require the entire circuit be redone to 4-prong? or does it require the just the new work to be 4-prong?

Best Answer

There are others (Harper, ThreePhaseEel) who will likely provide a ton of details. But in a nutshell:

  • 3-prong does not provide the same level of safety as 4-prong.
  • 3-prong is grandfathered in, but when you make a change you should switch to 4-prong. New work should definitely be 4-prong NEMA 14-30. I don't know if code strictly requires a change to 14-30 in your situation (the real pros can weigh in on that). But from a practical standpoint, once you are already doing the work you might as well spend a few $ on a new receptacle and new power cord and do it right (unlike my electrician years ago).
  • When you switch, in addition to the new 4-prong receptacle and new 4-prong dryer cord to match it, there is a ground-neutral bonding jumper that MUST be removed on the dryer.

Your pictures pretty clearly show that there is no existing ground, and you have also made it clear that a new cable back to the main panel would be quite expensive. If a retrofit ground using existing wiring (e.g., connecting to the ground of the washer receptacle, provided it is legal (large enough wire or other grounding mechanism)) is not practical then I would consider a combination of (a) replacing the regular breaker with a GFCI breaker to provide protection and (b) replace the existing 3-prong dryer cord with a longer 3-prong dryer cord to take care of the extra several feet. I do NOT recommend using an extension cord - they are available but that is not a good idea, and may even be against code for a nominally permanent installation.

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