Pete,
There was an exception that allowed use of the neutral as a ground for
cooking appliances, supposedly to save copper. (note Canada never
allowed this exception). It has since been removed from NFPA 70.
Likely your home was built when the exception was in force.
Fair Use Excerpt.(Copyright NFPA):
*250.140 Grounding (Bonding)---Ranges, Ovens, and Clothes Dryers.*
*The frames of electric ranges, wall-mounted ovens, counter-mounted
cooking units, clothes dryers, and outlet boxes that are part of the
circuit for these appliances must be grounded (bonded) to an effective
ground-fault current path by an equipment grounding (bonding) conductor
of a type specified in 250.118 [250.134(A)].Figure 250--181
Exception: For existing branch-circuit installations, where an equipment
grounding (bonding) conductor isn't present in the outlet box, the
frames of electric ranges, wall-mounted ovens, counter-mounted cooking
units, clothes dryers, and outlet boxes that are part of the circuit for
these appliances can be grounded (bonded) to the grounded neutral
conductor if all the following conditions are met:Figure 250--182
*
1. *The circuit is 120/240V or 120/208V. *
2. *The grounded neutral conductor is not smaller than 10 AWG copper or
8 AWG aluminum. *
3. *The grounded neutral conductor is insulated, or it's uninsulated
and part of a Type SE cable and the branch circuit originates at
service equipment. *
73 Martin Flynn
On 2/14/2012 5:11 PM, Pete Smith N4ZR wrote:
> I just installed a new GE Monogram range. It came with a 4-prong plug
> and cord, but with instructions for re-wiring to use a 3-wire circuit,
> which I did. In involved jumpering the chassis of the stove to the
> neutral wire. I have a hard time imagining that these instructions
> would have been given if they were not compatible with the NEC or UL.
>
> 73, Pete N4ZR
>
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