NEMA 10-30 to L6-30?

[Hobnob]

I've searched and can't find an answer. I'm working on my e-HERMS build and have a question about my 250v dryer outlet to run power to my control panel.

Here is what my dryer plug and receptacle look like below. It's NEMA 10-30. The receptacle has black, white and copper ground. Some sites say 10-30 isn't grounded, buy mine is grounded. My house was built in 1988.

Can I simply buy another 10-30 dryer cord, cut the terminal rings off and wire up a NEMA L6-30 or L5-30? Is this a common thing to do?

I am going to run this cord into an inline GFCI extension cord.

Hobnob

 

[jeffmeh]

NEMA 10-30 should have H-H-N, with no ground, but someone certainly could have wired it H-H-G with no neutral. That said, most dryers have both 120v and 240v circuits in them, and if that is true in your case, there should be a neutral. If you really have H-H-G, then you cannot derive 120v in your control panel, and will need to either confine yourself to 240v devices, or run a separate input from a 120v circuit.

Can you confirm that the supply wire to that dryer receptacle is H-H-G, or H-H-N, or H-H-N-G? Then you can use the appropriate receptacle, and know what options you have for your panel.

 

[Hobnob]

Thanks for your reply! It is H-H-G. My multimeter reads 125v when testing black and ground, then white and ground with the probes. Does this mean the neutral is acting as both the hot and neutral?


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[pizza_man]

I've searched and can't find an answer. I'm working on my e-HERMS build and have a question about my 250v dryer outlet to run power to my control panel.

Here is what my dryer plug and receptacle look like below. It's NEMA 10-30. The receptacle has black, white and copper ground. Some sites say 10-30 isn't grounded, buy mine is grounded. My house was built in 1988.

Can I simply buy another 10-30 dryer cord, cut the terminal rings off and wire up a NEMA L6-30 or L5-30? Is this a common thing to do?

I am going to run this cord into an inline GFCI extension cord.

Hobnob

In the older 3 wire standard neutral is ground - they are the same wire.

Even with the newer 4 wire standard neutral and ground are tied together in your electrical panel. The are run separate so that in the unlikely event your neutral wire opens you still have ground.

 

[jeffmeh]

Yes, they are the same wire. From the OP, is it a bare copper ground, or an insulated copper ground? If bare, and your dryer has both 120v and 240v, then you have a bare conducting wire, which is not good. If I misunderstood and it is insulated, then you have a neutral that you can use.

 

[Hobnob]

Yes, they are the same wire. From the OP, is it a bare copper ground, or an insulated copper ground? If bare, and your dryer has both 120v and 240v, then you have a bare conducting wire, which is not good. If I misunderstood and it is insulated, then you have a neutral that you can use.

The copper ground was in the romex along with the two other hots.

 

[z-bob]

IF the breaker for 10-30 receptacle is in your main panel, and if you do not live in a mobile home, the 3rd wire can serve as either a ground OR a neutral -- they are bonded together in the main panel.

If the breaker is in a subpanel, and if that subpanel is not in an outbuilding with a 3-wire feeder, the 3rd wire is technically a neutral and not a ground (also they should not have used a NEMA 10-30)

 

[Hobnob]

IF the breaker for 10-30 receptacle is in your main panel, and if you do not live in a mobile home, the 3rd wire can serve as either a ground OR a neutral -- they are bonded together in the main panel.

If the breaker is in a subpanel, and if that subpanel is not in an outbuilding with a 3-wire feeder, the 3rd wire is technically a neutral and not a ground (also they should not have used a NEMA 10-30)

Oh okay. Yeah, there is a 30 amp double pole breaker in the main box (non GFI) and I'm in a house, no mobile home or subpanel.

So... does this mean the outlet was wired up incorrectly with a 10-30R (3-pole, 3-wire), but really it should have been a 2-pole, 3-wire grounding receptacle (like a 5-30 or 6-30) since I have H-H-G?

 

[z-bob]

That is the receptacle used for electric dryers until... 1994, I think. And I assume it is wired correctly. IMHO, you can safely pretend it's a 6-30. The third wire is connected to both the ground and neutral because it goes all the way back to the main panel.

Old dryers and stoves used the 3rd wire as a BOTH a ground and a neutral connection, which for anything else is illegal. (it is connected to the frame, and also handles any unbalanced load from things like timers and lights)

 

[Hobnob]

Thanks for all the help on this! Based on those answers, please let me know if I'm on the right track:

- Since I have H-H-G, I could run a single, 10/3 cord to a 5500w element, no problem. I could plug it in and unplug it from wall -- no control panel -- but that would work with my current wiring if I wanted to.

- I wouldn't be able to derive 110v in my panel because I won't have an isolated neutral from the dryer outlet.

Can I run a 14/3 110v and utilize the 110's neutral in the panel to run my PIDs, pumps, etc.? Any other way to do this, or should I just go with dual 110v elements and give up on the 220v route?

Thanks,
Hobnob


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[jeffmeh]

If your shared neutral/ground is insulated, you can get a GFCI spa panel and do the 3-in, 4-out trick (with all of the various provisos, not to code, should be pluggable so you are not violating code with permanent wiring, not a true ground). Search this forum for more. It's a pretty decent solution for getting a GFCI and having both 120v and 240v circuits, when it is inconvenient to run a new 4 conductor wire.

If your shared neutral/ground is not insulated (bare copper wire), that is not good, because your dryer is likely utilizing it for a 120v circuit.

 

[Hobnob]

Ah okay. Yeah, it's a bare ground coming into the box.




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[jeffmeh]

OK, I am not an electrician, but I would have some concern about the bare neutral. I suppose that if the bare portion is confined inside the wall box, it likely won't pose a problem. Personally, I would not use that feed for a control panel with anything other than 240v circuits (no 120v). However, there are more knowledgeable folks on here than I, and I will defer to them.