3-wire dryer outlet to 4-wire help needed

[NinjaJoe]

Goal: Build a panel that will allow me to plug into the existing 3 wire dryer outlet (i have pulled the plate and confirmed that it is 3 wire and not 4 wire) while adding GFCI AND proper wiring for safety that provides 240v & 120v in my panel.

Question: How do I go from a 3wire outlet to a GFCI protected 4-wire input for my control panel?

What I can not change: This is a rental (and the distance between the main panel and the dryer outlet is quite far) so no pulling 4 conductor wire or a ground wire.

If my understanding is correct, a 3 wire dryer should be H-H-N (how to tell if it is H-H-N or H-H-G with an insulated G?) which would only allow for 240v. And that my only options would be to 1.) pull 4-wire, 2.)pull a ground wire, 3.) use a 240-120 transformer (but wouldn't be to code), 4.) bring in 120v from a separate outlet.

#1 & #2 are out. #3 would be nice as it wouldn't require to bring in 120v from a different outlet. #4 is a viable option as there is a 120v outlet very close to the 3-wire dryer outlet.

Thoughts/comments/concerns?

I have pulled the panel cover and the 30a breaker is highlighted below:

 

[NinjaJoe]

Would this be a solution?

 

[doug293cz]

Would this be a solution?
View attachment 680491

This will work, but it is not compliant with electrical codes.

Brew on

 

[passedpawn]

I'd replace the existing 240 breaker with a 240V GFCI breaker (i.e., H/H/N all feed into the GFCI breaker). Then, I'd pull a ground from a nearby outlet. I'm guessing that also isn't perfectly to code, but it's safe as long as that ground wire is properly protected from damage.

Even though you have a rental, I would probably replace the 3-prong outlet with the 4-prong (instead of making some sort of kludge adapter). I doubt anyone would ever notice, assuming you did it properly. I guess there's some risk there though. Pay an electrician to do it and you minimize your issues. BTW, dryer cords are really easy to change out - they don't eve ship with cords these days (I don't think) because of the two connector types.

 

[philm63]

If I'm understanding this correctly, if you pull a ground from a nearby outlet - assuming we're talking about a standard duplex at 125 V, 15 A, we're looking at a grounding conductor of 14 AWG.

If you're using this ground for protection on a 50 A GFCI circuit, under a typical short circuit condition there could be a fault current in excess of 15 A on that grounding conductor which would be enough to trip a 15 A breaker, but possibly not a 50 A breaker.

This means that you could have a fault in that 50 A circuit that generates a fault current greater than 15 A and if so, that 14 AWG ground wire is going to heat up. Too hot and you could start a fire.

 

[passedpawn]

If I'm understanding this correctly, if you pull a ground from a nearby outlet - assuming we're talking about a standard duplex at 125 V, 15 A, we're looking at a grounding conductor of 14 AWG.

If you're using this ground for protection on a 50 A GFCI circuit, under a typical short circuit condition there could be a fault current in excess of 15 A on that grounding conductor which would be enough to trip a 15 A breaker, but possibly not a 50 A breaker.

This means that you could have a fault in that 50 A circuit that generates a fault current greater than 15 A and if so, that 14 AWG ground wire is going to heat up. Too hot and you could start a fire.

It's a 30A ckt. But yea, that's a very good point - but with a GFCI on the circuit it's not an issue.

 

[ehall]

considering you're not quite sure what to do and its a rental. It would be wise to hire an electrician at the very least for advise and what the code is. you could burn the house down and if you survived you would be on the hook for the damage.

 

[Jtvann]

Go on amazon and buy an adapter. I did this for my first old house. They're not expensive at all and you wont be doing any type of wiring that you're uncomfortable with, and wont be messing with anything for your rental.

I may actually still have my old one laying around that I'm not using anymore. Let me know if you're interested by PM.

 

[doug293cz]

Go on amazon and buy an adapter. I did this for my first old house. They're not expensive at all and you wont be doing any type of wiring that you're uncomfortable with, and wont be messing with anything for your rental.

I may actually still have my old one laying around that I'm not using anymore. Let me know if you're interested by PM.

I don’t think there is such a thing as a code compliant adapter that converts a 3 wire (H-H-G) outlet into a 4 wire (H-H-N-G) outlet.

Brew on

 

[Hwk-I-St8]

If it were me, I'd run two power intputs to my box, one for 240, one for 120. Make the 240 input a 4 prong, but have nothing on the neutral line.

If/when you move, you wouldn't have to change much to pull your 120 from the 4 conductor 240 input if/when you have access to it.

That just seems less kludgy and your keeping all your voltages/amperages in sync with the wiring.

The only downside is having to plug in to different outlets.

Perhaps I'm missing something?

 

[Jtvann]

Might not be to code, I'm not an electrician. It does exist though and solves the problem to the question answered. Who knows what lawsuits exist on selling something like this against code?


https://www.ebay.com/i/332585516296...MIloTaurbI6QIVTNbACh26cAXUEAQYByABEgL25fD_BwE

 

[doug293cz]

Might not be to code, I'm not an electrician. It does exist though and solves the problem to the question answered. Who knows what lawsuits exist on selling something like this against code?


https://www.ebay.com/i/332585516296...MIloTaurbI6QIVTNbACh26cAXUEAQYByABEgL25fD_BwE

That cord goes 4-wire to 3-wire. No code issue there. OP needs 3-wire to 4-wire.

Brew on

 

[z-bob]

If the outlet is wired correctly, there is no difference between HHN and HHG. You can only have a 3-wire dryer circuit if it goes to the main breaker box where the ground and the neutral are bonded. (that's why mobile homes have had 4-wire dryer circuits for many years) HHN is I think actually more restrictive here; the N wire has to be as large as the H wires where a G could be 2 sizes smaller. It's also insulated, where a G doesn't have to be. I am not an electrician, so not totally sure about these.

Also, with a GFCI you don't need an equipment ground. So you should be able to use the hot wires as hot, the ambigious wire as a neutral, and either leave it ungrounded or borrow a ground from another circuit. (I would leave it ungrounded) Does the GFCI device itself require a ground? I wouldn't think so but I don't know. It probably requires a neutral.

 

[Bobby_M]

The early solution with the spa panel is the closest thing to your desire. It gets you GFCI and relatively safe 240/120v system. The is no code compliance issue because portable connections that attach to house wiring is not under the purvue of electrical codes. That is, as long,as the spa panel is fed with SJ cord with a plug on it.

Even if you pulled the 120v from a different circuit, there is still the matter of using a neutral as an earth ground which is definitely not to code.

 

[doug293cz]

...

Even if you pulled the 120v from a different circuit, there is still the matter of using a neutral as an earth ground which is definitely not to code.

Could use the ground from the 120V cord as earth ground.

Brew on

 

[doug293cz]

...

Also, with a GFCI you don't need an equipment ground. So you should be able to use the hot wires as hot, the ambigious wire as a neutral, and either leave it ungrounded or borrow a ground from another circuit. (I would leave it ungrounded) Does the GFCI device itself require a ground? I wouldn't think so but I don't know. It probably requires a neutral.

GFCI's can fail, so an earth ground tied to any metal in the system is still required to minimize risk to people.

A GFCI needs either a ground or neutral for the test circuit to work. The GFCI can operate without gnd/neut, but you have no way of insuring it is still working.

Brew on

 

[Bobby_M]

Could use the ground from the 120V cord as earth ground.

Brew on

You could, but will the 30 amp breaker trip before the 14 gauge ground vaporizes? Probably. Hopefully.

 

[doug293cz]

You could, but will the 30 amp breaker trip before the 14 gauge ground vaporizes? Probably. Hopefully.

Yes it will. I've seen 2A put thru ~600 sq um (600 square micrometer) cross section, and Cu didn't melt. Dielectric discolored over 100's of hrs. 14AWG wire is 2,080,000 sq um cross section. 14AWG wire has a resistance of 2.52 m-ohm/ft, so the heat generated per ft at 30 A would be 30*30*0.00252 = 2.27 W/ft. Not going to fry any Cu at that energy density.

Brew on

 

[z-bob]

I don't know why you care about code or the rental part, just don't make any changes to the house wiring. You do care that it's safe. Connect the GFCI with a plug and cord instead of putting it in the breaker box and as someone said already, it's outside the purvue of the electrical code.

It is also safe to use the 3rd wire of a dryer or range outlet as either a ground or a neutral. (the dryer uses it for both, taking advantage of an old code exception just for dryers and electric ranges) At the breaker or fuse box end, it is connected to both the earth ground and the neutral bar; if it wasn't (because it originated in a subpanel instead of the main panel) it would have to be 4 wires. I'm not suggesting that you use it for both a ground and a neutral; use it for one or the other.

 

[beto998]

The 240V:120V transformer IMO is the easiest safe way to go about this. Should be code too if you wire it right. You need to treat the 120V as a separately derived source and bond it by tying one side of that to the ground from the 240V circuit. This side becomes your neutral in the 120V circuit. Note that even though you have tied to the ground in the 240V panel as your 120V neutral, there is no current on the 240V ground wire - all your neutral current is to the transformer. You could also put the GFCI breaker (a panel mount or din mount, not the stab type) into your own panel - also supplying the 120V transformer, in case of some failure of the transformer or in your 240V load, the GFCI will trip. Any reasonable size would work, I use a 63A GFCI on a 30A circuit. No modifications to the rental, and everything you invest in is now portable to a new home. It would be safe, probably to code, but even if it isn't, you unplug one cord and you are code compliant again.