neutrals for appliances

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JeffD

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I'm an electrical engineer that works for a general contractor. We are doing a high rise residential project. The project has electric ranges. The ec has been asking from the beginning of the project if a neutral was required. No one has been giving him a straight answer and that is why I got involved. The engineered dwgs just show 2 hots and a ground. All of the specs say 3 or 4 wire is fine. I called GE to see if a neutral was required and if not how did the clock and timer get their power, a nearby 120 volt circuit or what? GE said that there is a bonding strip between the ground and the neutral at the appliance. If the neutral is run you break that strip. If a neutral is not run you just leave the strip in place and that is how the neutral is derived. If I'm hearing this conversation right they are saying they are using the ground as the neutral when no neutral is pulled, and I don't believe this is allowed. I work mainly commercial and institutional projects and don't see many appliance installations so I would appreciate it if anyone can tell me if I am missing something even if it is basic.

Thanks,
 
Here is what the NEC says about this

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, wye-connected 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 service-entrance 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.


250.142 Use of Grounded Circuit Conductor for Grounding Equipment.
(A) Supply-Side Equipment. A grounded circuit conductor shall be permitted to ground non?current-carrying metal parts of equipment, raceways, and other enclosures at any of the following locations:
(1) On the supply side or within the enclosure of the ac service-disconnecting means
(2) On the supply side or within the enclosure of the main disconnecting means for separate buildings as provided in 250.32(B)
(3) On the supply side or within the enclosure of the main disconnecting means or overcurrent devices of a separately derived system where permitted by 250.30(A)(1)
(B) Load-Side Equipment. Except as permitted in 250.30(A)(1) and 250.32(B), a grounded circuit conductor shall not be used for grounding non?current-carrying metal parts of equipment on the load side of the service disconnecting means or on the load side of a separately derived system disconnecting means or the overcurrent devices for a separately derived system not having a main disconnecting means.
Exception No. 1: The frames of ranges, wall-mounted ovens, counter-mounted cooking units, and clothes dryers under the conditions permitted for existing installations by 250.140 shall be permitted to be grounded by a grounded circuit conductor.
 
It is the common lot of electrical engineers to have to design projects without clear and certain knowledge of the requirements. The selection of equipment takes place long after our design drawings are scheduled to be issued. As much as you try to get the mechanical engineers and the people responsible for choosing kitchen and laundry equipment to tell you what they are going to install, you never get the final answer in time to complete your design.

So the best you can do is to try to accommodate more than might actually be installed. You design a branch circuit for a 15 HP motor, knowing that it likely to wind up being under 10 HP. But it is easier to make a change to a smaller and cheaper branch circuit than to have to justify upsizing it.

So I would recommend including 4-wire circuits for the ranges in all units. It would be easier to accommodate a given range happens not to need the neutral than it would be if you installed a 3-wire system and they wound up buying ranges that need the 4-wire.
 
I sent a rfi to the engineer telling him I think a neutral should be pulled. I'm sorry for not being clear in my question. My main question is why is GE saying you don't need a neutral? IMO I think one is required and it is wrong to bond the neutral and the ground at the appliance. They told me it is ok to do that. Is there something I don't know about that says it is ok?
 
JeffD said:
I sent a rfi to the engineer telling him I think a neutral should be pulled. I'm sorry for not being clear in my question. My main question is why is GE saying you don't need a neutral? IMO I think one is required and it is wrong to bond the neutral and the ground at the appliance. They told me it is ok to do that. Is there something I don't know about that says it is ok?
Click to expand...

It is not okay on a new installation
 
It USED to be acceptable to do what GE is suggesting. I think the code req's changed in either the 93 or 96 code cycle. The manufacturer's now find themselves in a bit of a pickle. They have to design their products so that Joe Homeowner can prchase a new range or dryer and use it with his existin circa 1970something wiring or with his brand new home wiring. The existing pre-1993 receptacles will almost always be of the 3-wire type not containing a neutral. It is a code violation in new construction (see code quotations in previous posts) to install a new range or dryer receptacle that is not 4-wire.
 
GE may have mentioned either installation practice, not knowing if the apartment building was new. There are a lot of existing apartment complexes that upgrade their ranges. Since the receptacle is existing it most likely is a 3-wire installation.
 
GE probably has no clue about the NEC.


Why cant they just make those stupid clocks inside the ranges 240V. That would be soooo much easier.
 
jes25 said:
GE probably has no clue about the NEC.
Click to expand...
GE doesn't have to have a clue about the NEC. They make appliances. New ranges usually come without a cord, because they have no way of knowing whether a 3-wire or 4-wire circuit and receptacle are in the premises.

The new circuit is what must be done according to the code cycle in effect in the locality in question, and then the appliance properly fitted with a cord suitable to the installation..
 
First of all, if only three conductors are installed, it is the grounding conductor which is missing. Older versions of the code allowed ranges and clothes dryers to be grounded via the neutral (grounded conductor). My understanding is that this practice was begun during World War II in an effort to save wire (as it eliminated one conductor). It took 50 years for us to realize that the war was over and that "neutral grounding" was no longer needed and that ranges and dryers should comply with the same requirements as other appliances. The clock, lights, and on low heat some heating elements operate at 120-volts. So replacing the clock with a 240-volt clock would not eliminate the need for a neutral at the appliance. Beginning with the 2002 code a grounding conductor AND a neutral conductor are required for new construction. You may install a new range to the existing 3-wire circuit in an existing building, but new circuits MUST be 4-wire.
 
My wife goes down to a local supplier and buys the appliances for the house we are building - includes a countertop range and a separate double oven. I don't open the boxes cause I don't want to get the stuff beat up, so I check the mfg website using the model numbers off the boxes and get the installation data. A 2p, 40A ckt each. I install a 3W w/G to each - this is this year and we all know new construction requires 4W range and dryer ckts.

I finally open the boxes and the double oven has six feet of flex with 4 wires. The range top has 4 feet of flex with two hots and a bare ground. Hummmm Both are GE.

I'm bad mouthing GE plenty while looking for a piece of white highly flexible 105C wire to put into the rangetop flex for the neutral. I mean these goofs have to know about the code requirements for ranges.

I finally find a peice of suitable wire and pull the cover off the bottom of the rangetop - no neutral connection, no evidence of any 120V connection or equipment. No clock, no timer, no light. Hummmm again.

So I hook up the two hots and the ground and just cap the white. Turn on all the burners and clamp on an ammeter. The burners modulate by switching on and off. When they are on you can see the red glow through the glass right now. When modulated off (at temp), they are black in seconds. With all four burners on medium high, the current jumps from about 10A to 27A depending on how many burners are pulling current.

No neutral required. Its really hard to suck back all of the verbal bullets I flung at GE. But I did. :oops:

carl
 
Carl, the appliances you describe are not 'ranges' to the NEC so 250.140 would not apply in any case.

You have a counter-mounted electric cooking unit and wall ovens. :wink:

IMO It would not be code compliant to hook up a wall oven to a 3 wire existing circuit if the unit is rated 240/120
 
iwire said:
...You have a counter-mounted electric cooking unit and wall ovens....
Click to expand...

Yup. I got that - finally (maybe). This is likely an example why I don't try to do electrical installations for pay. I'd starve to death. :roll:

carl
 
iwire said:
Carl, the appliances you describe are not 'ranges' to the NEC so 250.140 would not apply in any case.

You have a counter-mounted electric cooking unit and wall ovens. :wink:

IMO It would not be code compliant to hook up a wall oven to a 3 wire existing circuit if the unit is rated 240/120
Click to expand...
Bob, I disagree. An existing circuit is exactly what is covered by:

250.142 Use of Grounded Circuit Conductor for Grounding Equipment.
Exception No. 1: The frames of ranges, wall-mounted ovens, counter-mounted cooking units, and clothes dryers under the conditions permitted for existing installations by 250.140 shall be permitted to be grounded by a grounded circuit conductor.
 
LarryFine said:
Bob, I disagree.
Click to expand...

Hey porcupine you can't disagree! :evil: :twisted:



Just kidding, you should disagree as I was wrong. :oops:


LarryFine said:
An existing circuit is exactly what is covered by:

250.142 Use of Grounded Circuit Conductor for Grounding Equipment.
Exception No. 1:
Click to expand...

Actually I had looked up 250.140.

250.140 Frames of Ranges and Clothes Dryers.
Click to expand...

Which is the actual code section that allows the use of the grounded conductor for grounding these items (250.142 Exception 1 directs us to 250.140.)

The problem was in my not reading past the first few words. :oops:
 
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