Code requirements for moving 3 prong dryer outlet

Question

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?

Answer 1

Since the 1999 NEC, if you modify this branch circuit to extend it then you need to upgrade it to a properly grounded NEMA 14-30 outlet or it will not meet code. Most AHJ require an electrical permit to wire this extension and what you propose will not pass inspection.

From 2011 NEC below with my emphasis. Note that "grounded circuit conductor" is NEC-speak for the white neutral wire in your existing installation.

250.140 Frames of Ranges and Clothes Dryers. - - Frames of electric ranges, wall-mounted ovens, counter-mounted cooking units, clothes dryers, and outlet or junction boxes that are part of the circuit for these appliances shall be connected to the equipment grounding conductor in the manner specified by 250.134 or 250.138.

Exception: For existing branch-circuit installations only where an equipment grounding conductor is not present in the outlet or junction box, the frames of electric ranges, wall-mounted ovens, counter-mounted cooking units, clothes dryers, and outlet or junction boxes that are part of the circuit for these appliances shall be permitted to be connected to the grounded circuit conductor if all the following conditions are met.

(1) The supply circuit is 120/240-volt, single-phase, 3-wire; or 208Y/120-volt derived from a 3-phase, 4-wire, wye-connected system.

(2) The grounded conductor is not smaller than 10 AWG copper or 8 AWG aluminum.

(3) The grounded conductor is insulated, or the grounded conductor is uninsulated and part of a Type SE service-entrance cable and the branch circuit originates at the service equipment.

(4) Grounding contacts of receptacles furnished as part of the equipment are bonded to the equipment.

Note that the grounding wire can be a retrofit and it doesn't have to be a home run back to the service panel. For example if you have a common grounded 110V outlet (NEMA 5-15R) nearby you can bond to this ground if the branch circuit goes back to the same service panel.

Here's a snippet of NEC that talks about retrofit grounds:

250.130(C)(1) A non-grounding type receptacle can be replaced with a grounding-type receptacle if an equipment grounding conductor is installed and connected to any accessible point on the grounding electrode system.

250.130(C)(2) A non-grounding type receptacle can be replaced with a grounding-type receptacle if an equipment grounding conductor is installed and connected to any accessible point on the grounding electrode conductor.

250.130(C)(3) A non-grounding type receptacle can be replaced with a grounding-type receptacle if an equipment grounding conductor is installed and connected to the equipment ground terminal bar within the enclosure where the branch circuit originates.

250.130(C)(4) A non-grounding type receptacle can be replaced with a grounding-type receptacle if an equipment grounding conductor is installed and connected to an equipment grounding conductor that is part of another branch circuit originating in the same enclosure.

Answer 2

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.

Answer 3

Your options here

You have several options here for making this safer and Code-compliant:

1. Rerun the circuit with a grounded cable (awkward, I know, but probably not impossible). This way, you could also put in a proper box and flushmount receptacle (surfacemount type NEMA 14s exist, but they are annoying compared to the box-mounted counterparts)
2. Switch the receptacle for a NEMA 14, swap the breaker for a 30A two-pole GFCI (may not be possible if the breaker's a quadruplex/half-width type), and put the requisite "No Equipment Ground" and "GFCI Protected" labels on it, as per 406.4(D)(2)(c).
3. Retrofit a 10AWG ground wire back to a suitable grounding point in the electrical system (note: not a water pipe), as per 250.130(C). You'll also get to upgrade the receptacle to a NEMA 14 this way.

Given that option 1 is going to be a pain in the arse for you, and option 3 an equal pain in the arse, I'd recommend option 2, although you'll need to patch a junction box in where the existing surface mount receptacle was located in order to extend the wires to the new location if you do that. You'll also want to make sure you can fit a 30A, 2-pole GFCI breaker into your panel before you start shopping for parts for that.

With all of these three options, you'll be fitting a 4-wire cord to the dryer and pulling the bonding jumper from it.

Answer 4

I see 2 options.

1. Run a totally new cable from the panel to the new location. Ouch. This is the "by the book" procedure.

2. Retrofit ground to the old location. Have this already installed, in place, and in service. Then, after a lapse of some amount of time (other than zero), preferably with an inspector visit inbetween, then extend this circuit from the old location to the new location as 4 wires.

Here's what you can't do.

3. nope Use the "GFCI+No Equipment Ground" trick, and then extend to the new location. Code requires new work have a proper ground, period.

4. nope Retrofit ground to the new location. New locations must be built to current Code. You're not allowed to retrofit ground to new work.