Electrical Question

[Mike Goetzke]

I'm installing a cooktop in a kitchen island. The appliance requires a 50A 220V breaker. The appliance has a green/ground and two hots/red&black. The instruction manual shows two ways to wire it:

1) Supply two hots and a neutral. Ground neutral & green from appliance to the electrical box. Connect hots.

2) Supply two hots, neutral, & ground. Ground ground & green from appliance to electrical box. Connect hots. And for some reason the white/neutral gets capped off.


Any reason not to do # 1???


Thanks,

Mike

[Thomas Bank]

In the first line you say the appliance has ground and two hots, but no neutral?

Second line says "neutral & green from appliance" - so is there a neutral?

Third line again implies no neutral from appliance.

If the appliance is 220V only, then no need for a neutral and I'd do #2. Bad form to tie the neutral and ground together at the appliance. But if the appliance has 110V as well, then I'd do four-wire. Hot to hot, hot to other hot, neutral to neutral, and ground to ground.

[Mike Goetzke]

See below. Don't understand the logic in the four wire diagram on the right hand side but thinking this is how I need to do it. Maybe it's like that so some idiot doesn't try to branch off the outlet w/o a neutral:

[Dave MacArthur]

They gave you options for a electrical supply box with 3 wires in it, or 4 wires (hot, hot, neutral, bare ground). Why? Because some people have a 220 with 3 wires, some with 4--it's a simple answer, do you have 3 or 4 wires there?

The short of it is, any wire you use for it's non-standard purpose you need to clearly mark, and if you don't HAVE to mis-use a wire then don't.
--if you already have a red, black, and bare ground or green, then hook those 3 up and CAP the neutral.
--Your picture clearly states you may not ground to the neutral wire (first option) if it's a new branch circuit or where local codes do not permit. Anyplace that has adopted recent NEC does not permit this, and it's bad and risky practice anyways--I would not do it. Why? Because the neutral wire can carry a lot of current on it, and it may not go to ground before it electrifies your appliance. Now, of course that doesn't apply if your wire is just a dedicated circuit like it should be.

There's another option here, which is really the most LIKELY option-- your appliance doesn't need any 120V, it's just hooked up to the two hot wires, so you only need 2 wires and a ground. There's no reason to have a 4-wire hookup, when 3 wires will do... that first picture doesn't show a ground present, and that's not going to happen, so if it's a dedicated circuit then just tape the entire end of the white wire red, on BOTH ENDS--appliance and breaker box--and use the white wire as a hot, then wire the ground/green/bare normally.

If you've got 4 wires, then use picture #2.

[Ron Natalie]

If you are pulling new wire you MUST NOT DO #1.
You MUST DO #2.

In days gone by, stoves were allowed to be grounded via the neural (white) wire. The current code requires a separate ground and neutral. It allows the grandfathering of existing wiring, but if you're pulling new wires, you must pull the ground. I'd go ahead and pull in the white wire (neutral) even if it isn't necessary for this unit because someday it might be replaced with one that requires it.

I suspect you will be pulling new wiring. Most existing cooktops were only set up with 30 or 40A circuits...those 50A induction units are going to need bigger wire.

[Jim Neeley]

If you're running new wire then +1 on both Dave and Rons posts.. with a clarification.

Ron, please note that Dave is talking about a white/black/green combo.

Clarification: You can either run cable per #2 (3 conductor + ground) or a modified version of #1 if you only have 2 conductor + ground cable.

Please be aware that the ampacity tablers in the National Electric Code require a minimum of #6 cable (or #8 if you have 75*C insulation) so this is much heavier than anything you're likely have lying around the house and as Ron says, likely larger than what's in place. [What's in place is likely #8 with 60*C insulation or #10 with 75*C insulation.]

Option #1, can be used as long as you tape both ends of the white wire red (as Dave has indicated) and use the green (ground) where the #1 shows the white wire (connecting to the screw in the back of the box).

In any event, in your electrical panel the green wire must go to the ground bus, not the neutral bus. As the guys ahead of me have said, the neutral bus in your power panel carries lots of current from the other circuits in the panel.

Dave & Ron, please correct me if I have inadvertantly misspoken but since I've got the NEC open bedside me, that's likely onlyto come from a typo. <g>

Finally, these sizes assume that you are using copper wire, not aluminum [aluminum would have tobe even larger]. Also, aluminum wire is illegal in many jurisdictions and, IMO, should be illegal in even more!

[Mike Goetzke]

Thanks for all the help. I ended up pulling three #6 wires plus a ground and used diagram # 2. Good thing I had two of my kids around to pull those monster wires.

The induction cooktop is awesome - the commercials are right, it boiled about 2" of water in less than 2-minutes.



Mike

[Dave MacArthur]

Awesome, great to hear! Mike, I'd really like to hear more about the induction cooktop, if you'd care to post the brand, and if you need special pots or what? I've got mostly All Clad cookware, put up a link to your brand unit or some info? Very interesting.

[Dan Hintz]

No special cookware other than cast iron type... any aluminum pans will need to be used elsewhere. Of course, if you're a serious cook, you shouldn't have much aluminum in the kitchen anyway

[Thomas Bank]

See below. Don't understand the logic in the four wire diagram on the right hand side but thinking this is how I need to do it. Maybe it's like that so some idiot doesn't try to branch off the outlet w/o a neutral:

I have to say that I'm confused more than ever by the diagram. Unless I'm missing something, it is saying that it is 220V only - no 110V. So you'd wire it to the two hots and the ground the same as any other 220V equipment. So why they're suggesting on the left to run two hots and a neutral and then connect the ground from the appliance to the neutral from the panel? Again, on the right, why would you bother running four wires only to cap off the neutral?

The issue with the old three-wire systems for a range or a dryer was that you were running the neutral on the appliance to the ground from the panel and if you had something short out you could end up with the chassis of the appliance being energized and shock someone. So they went to the four wire system so that you had a separate ground and neutral. But the diagrams above don't even enter into that issue...