Off Topic Electrical Question

[Frank Boettcher]

Well, cabinet trim went fine, range fits and is centered (probably should have greased the sides a bit goilg in) currently wiring the new range.

romex into the 50 Amp wall plug is three wire, which was code acceptable then and now for reinstallation. However, old range was wired with a four wire plug. Nuetral and ground are tied together in the male end of the plug (which I am reusing).

four wire hookup calls for hooking up black, white (nuetral) and red on the terminal block and *removing* a bonding strap from the ground screw to the nuetral terminal on the ground, then attaching the ground wire to the now chassis only ground screw.

Three wire hook up calls for black, white (nuetral) and red, no ground wire and leaving the bonding strap in place.

I'm going to assume that the former is better despite the fact there is no separate nuetral and ground returning to the box, they are at least separate leaving the appliance.

Or maybe it doesn't matter?

Frank

[Mike Marlow]

The only time it's "better" to have a neutral is when the appliance relies on a 110V leg for such things as timers, etc. Returning back to the box separately is meaningless. You are equally safe, equally beneficial, equally proper by using the three wire configuration as depicted in the second example.

[Chris Friesen]

By the same reasoning one could argue that there is no reason to have a ground pin on a 120V appliance.

The separation of neutral and ground gives additional protection against a fault in the neutral wiring, given that it's not practical for a metal-bodied stove to be double-insulated.

Chris

[Tom Veatch]

Assuming the range requires a 110 leg, a neutral is required. Current code requires a ground wire separate from the neutral which means under today's rules, wiring the range would require a 4-wire (3 conductor + ground) cable.

The three wire hookup you describe, bonding neutral and ground at the plug, violates the code requirement that the grounding wire not carry current during normal operation since bonding causes the neutral and ground to become a common conductor.

However, if, as you state, the 3-wire installation was per code at the time of the original installation and your local jurisdiction doesn't require that the installation be brought up to current code requirements on re-installation, you should be good to go. It does seem a little strange to me that a 4 wire receptacle would be permitted in a 3 wire installation. Could be very misleading to all who come later.

Tom Veatch Wichita, KS USA

[Mike M]

Code doesn't allow the nuetral (grounded conductor) and the ground (grounding conductor) to be tied together. However in past codes there have been exceptions for ranges which allowed the grounded and grounding conductor to be tied together on ranges and I think dryers. Its been so long since I've done residentual I'm not sure if it still exists. If I get a chance I'll check the code book.

Mike M

[Mike M]

This is still present in the 2005 NEC but notes show it has been edited.

Mike M

250.140 Frames of Ranges and Clothes Dryers. Frames of electric ranges, wall-mounted ovens, counter-mounted cooking units, clothes dryers, and outlet or junction boxes that are part of the circuit for these appliances shall be grounded in the manner specified by 250.134 or 250.138. Exception: For existing branch circuit installations only where an equipment grounding conductor is not present in the outlet or junction box, the frames of electric ranges, wall-mounted ovens, counter-mounted cooking units, clothes dryers, and outlet or junction boxes that are part of the circuit for these appliances shall be permitted to be grounded to the grounded circuit conductor if all the following conditions are met. (1) The supply circuit is 120/240-volt, single-phase, 3-wire; or 208Y/120-volt derived from a 3-phase, 4-wire, wyeconnected system. (2) The grounded conductor is not smaller than 10 AWG copper or 8 AWG aluminum. (3) The grounded conductor is insulated, or the grounded conductor is uninsulated and part of a Type SE serviceentrance cable and the branch circuit originates at the service equipment. (4) Grounding contacts of receptacles furnished as part of the equipment are bonded to the equipment.

[Frank Boettcher]

Yep, I'm aware of that. The installation instruction even refers to it. But also refers to the reinstallation being allowable as a three wire.

I may have confused with my terminology. The receptacle was three wire, but the old unit was hooked up as four wire. And it was confusing to me. I actually took the male plug (three wire configuration but four wires going in) apart to determine what was going on. Only thing I can think of is that the old unit did not have a ground bond, chassis to terminal block.

As far as the 110 requirement, I always thought the lights, timers, etc. were on a 110 leg. Is that not the case?

[Doug Miller]

They are, which is why you have to have at least three wires for it to work. The heating elements will run just fine with only two.

[Tom Veatch]

On Wed, 14 Nov 2007 08:31:26 -0600, Frank Boettcher wrote: ...

That is the typical case, and the reason that a neutral conductor is required - or, I guess in your case, a combined neutral/ground conductor.

Tom Veatch Wichita, KS USA