Question for the electricians--ok to run a 3-wire power cable from a 4-wire outlet?

[Horseflesh]

I ordered an electric system which I expected to require a 4-wire outlet. When it arrived, it was actually configured for a 240V 3-wire outlet plus a separate 120V supply. (Grr.)

I can easily supply the control panel with the 240V it needs by tapping the 2 hots and the ground on my 4-wire receptacle, and simply disregarding the unneeded neutral.

Question is, is that kosher? It seems safe but I'm not an electrician. For all I know the neutral may be required by the GFCI breaker, and this would be a bad idea.

Thanks for the help!

 

[DarkNoonBrewer]

This is Kosher. The only time you need the neutral is for a 120V use, or inside the breaker panel, where the neutral wire that comes off the GFCI needs to the neutral bus.

 

[mredge73]

What isn't kosher is using the ground as a current carrying conductor; don't do that.

Your plan is fine but I would use a 4-wire plug as to not require a separate 120v supply.

 

[Horseflesh]

The panel is already wired for separate 120V and 240V supplies. The manufacturer said that this is required for UL listing. Non-UL listed products from the same company use one 4-wire power connection for everything.

I have a wiring diagram showing where to connect 1 ground and 2 hot lines inside the panel. That's how they build them--they just forgot to actually attach my 240V power cable when they shipped it. You're saying that this isn't how it should be done?

 

[mredge73]

If the ground attaches to the chassis then it is fine. If it is used in place of a neutral then it is not fine.

A single UL test session can cost upwards to $25K, I am surprised that they would pay this much and still offer a non-UL assembly.

 

[Horseflesh]

In this case the ground is definitely connected to the chassis. Thanks!

Beats me about the UL strategy. The vendor offers home and commercial versions. I chose an upgrade for my home model which used some of the commercial parts, and the UL rating came along with it.

 

[mattd2]

If the ground attaches to the chassis then it is fine. If it is used in place of a neutral then it is not fine.

A single UL test session can cost upwards to $25K, I am surprised that they would pay this much and still offer a non-UL assembly.

It sounds like they sell a unit with a single power feed with a hot, hot, neutral, earth plug that is non-UL, as well as the UL separate 240 / 120 plug version.
What is weird is their claim that they can not get UL if they use a single plug for both 240 and 120. I don't know if that is true but it doesn't seem correct to me? Anyone know either way?

 

[Horseflesh]

You're exactly right about the 2 versions.

They told me that UL forbids having an electric heater and a motor--the pump--on the same feeder circuit.

 

[mattd2]

That sounds a bit suspect - after all most factories only have a single feed coming into their buildings so it is going to be on the same feeder circuit from some point. And motor / element is not the same a 240 / 120.
I can understand separating the circuit protection for inductive/resistive loads, but not the feed into the box!

 

[DarkNoonBrewer]

I must have missed this. Who made the controller in question?

 

[Horseflesh]

I didn't mention it at first because I didn't want to sidetrack the "will I fry myself" question with vendor discussion. It's http://www.cobrewingsystems.com/ though.

 

[lschiavo]

They told me that UL forbids having an electric heater and a motor--the pump--on the same feeder circuit.

UL forbids dishwashers?

 

[Horseflesh]

Beats me man!

I did see UL 508A listed on their site, if that means anything.

In any case mine is heating some water to 150F right now and all is well.