Hey, all of you electricians....

[Walker]

I know this is going to get me a lot of "don't do that!" responses from the general masses, but I would like to hear from legitimate electricians on this.

Will a NEMA 5-20 receptacle handle 240V, provided I stay under the 20A rating?

The reason I ask is because I would like to have GFCI protection on the receptacles, but finding 240V GFCI items is hard and they are expensive.

If I were to wire the hot and neutral connections of the 5-20 receptacle to the two hots of my 4-wire 240V source, would it handle driving a 240V item with... say... 10 amps and provide me with the GFCI protection?

.... OR ....

Does the GFCI circuitry on such a receptacle really only work with 120V differential?

 

[Hermit]

I had to tell a guy he trashed a refrigerator because he moved into a home that someone had done something similar so he plugged his 120V unit into 240V. That said, someone posted saying the return path on the hot must show up on the neutral. Not going to happen with what you are proposing since ZERO current will show up on the neutral.

 

[Walker]

I had to tell a guy he trashed a refrigerator because he moved into a home that someone had done something similar so he plugged his 120V unit into 240V. That said, someone posted saying the return path on the hot must show up on the neutral. Not going to happen with what you are proposing since ZERO current will show up on the neutral.

With what I am talking about here, current will show on the "neutral" connection of the receptacle, because it will be connected to one of the hots of the 240V service. Current through one port of the receptacle will be equal to current through the other port of the receptacle.

Also, I am not considering putting this funky wired outlet on any wall of my house. It would be on the back of a control box for my HERMS set-up, so nothing will ever get plugged in there by anyone other than me, and I would know that it was 240V, even though it LOOKS like 120V.

 

[Walker]

forgot to add... I am looking at the IC used to build these GFCI outlets. It looks like the IC itself would work fine, but the IC requires DC voltage to drive it, and that DC voltage is generated with a full-wave rectifier and step-down reisistor in the full GFCI circuitry.

So.... I don't think it'll work at 240V. Not because of where current is or is not flowing, but because the IC embedded in the outlet will be getting too much input voltage to operate properly.

 

[Walker]

It's not really worth discussing since it looks like the way the receptacle is put together depends on 120VAC to derive the proper DC voltage for the GFCI circuit to operate, but here's what I was trying to convey.

4-wire 240V service has two hot wires (red and black) each swinging +/- 120V but on opposite phases. It has a white neutral line and a green ground line.

For devices that need pure 240V, the white neutral is not used and only the red and black hot wires are used. I was proposing to hook the two hot lines to the outlet so that there was 240V potential from one port to the other, which would still give the GFCI circuitry two points at which it could monitor the current flow to find a net sum of "0".

 

[Ricand]

You might want to do it internally. Pull the 220, making sure you have a neutral and ground, you could run two cheap GFCI's inside the box and take the two hot leads from those and combine them into the appropriate shaped 220 outlet. It should give you GFCI on both legs and the proper outlet. Having said that, I take absolutely no responsibility for the smell of burning flesh and hair in your brew shop should this tip be entirely wrong.

OTOH, how much is your life worth? Over $65?

http://cgi.ebay.com/Cutler-Hammer-G...emQQptZLH_DefaultDomain_0?hash=item4a9e230d83

 

[Walker]

I don't think that would work. There will never be any current on the neutral line in my application... it's not connected to anything.

both of those intenal GFCI's would trip because one out see 100% current going out and none coming in, and the other would see 100% current coming in and none going out.

I am going to buy the 2-pole GFCI breaker. I was just curious and thinking outloud.

 

[feyr47]

after reading all your posts on this subject I think your best idea is your last one. go with a gfi breaker its expensive but its the most simple. I'm a big believer in KISS.
professionally I am industrial automation tech with a AS degree in electronics, and started out as an electrician.

 

[Walker]

Got a great deal on the 2-pole gfci breaker on ebay yesterday. $36 shipped, new in box.

 

[Bernie Brewer]

Walker, correct me if I'm wrong, but I seem to remember you telling me that you are an electrical engineer. You should know better!:cross:


If you're gonna do it, do it right. Use theGFCI breaker

 

[Walker]

I am an electrical engineer, an understand the basics of how GFCI works.

The voltage on the lines that the GFCI is monitoring seems irrelevant. It just watches the current flowing in and out of the system uising a coil wrapped around the supply lines and some EM field trickery (very clever, actually).

But, now that I know that the circuitry involves an IC and requires a certain DC voltage, which they derived from the AC source on the lines, I can see that when you buy in a store will not work. If you had a way to feed the GFCI circuitry with a separate voltage source than what you were trying to switch, it seems like it might work.

Anyway.... I see an electrical engineer and an electrician as just about the same as a mechanical engineer and a mechanic. My father is a mechanical engineer, does some stuff himself, but takes the car to a mechanic for opinions and more difficult work.

I am the same. I can DIY for some things, but when I don't understand something, I go to an electrician. The skills and knowledge are completely different.

 

[feyr47]

yeah i hear ya on the knowledge base thing, i fall somewhere inbetween the two. interesting about the ic deal, I'd try to dig up an older gfi breaker that works on the older non ic principals. do you have a surpuls industrial supply store in your area? I find so many nifty automation and control gadgets buried on shelves if i had to buy them new. im currently unemployed/underemployed so cash is tight. I'm currently looking for a 2 or three wire RTD for an temp control mash tun. preferably one with an armoured cable.

 

[Bernie Brewer]

Sorry, Walker, didn't mean to insult, honest.

 

[Walker]

No,no,no... I wasn't insulted or anything like that.

Sorry if I came off that way.

You still love me?

 

[Hermit]

Not if you look anything like your avatar. OK. I admit it, I'm shallow.

 

[Walker]

Watch it! That's a picture of my dear old mom.
















j/k

 

[Yooper]

No,no,no... I wasn't insulted or anything like that.

Sorry if I came off that way.

You still love me?

Awwwwww.


get a room.