Does table 250.122 preclude the use of #16 AWG wire as the equipment grounding conductor even if the circuit is fused at 1 ampere?
No 250.122A reads:
(A) General. Copper, aluminum, or copper-clad aluminum
equipment grounding conductors of the wire type shall not
be smaller than shown in Table 250.122, but in no case
shall they be required to be larger than the circuit conductors
supplying the equipment.
So if the ungrounded conductor is 16 AWG, the EGC can be the same.
Good question! If the equipment grounding conductor you are referring to is for a "branch circuit", then 210.19(A)(4) requires the egc to be a minimum #14awg unless specifically allowed in 210.2(specific purpose branch circuits).
Also, 250.122(A) says that the egc shall not be smaller than Table 250.122, "...but in no case larger than the circuit conductor...". Many code experts understand this to mean that #14 is the minimum and if the circuit conductors are #14 or larger, then and only then, need not to be larger than the circuit conductors, unless in parallel(250.122(F).
If you are fused at 1amp, I doubt that you are referring to a branch circuit. In addition, if you are following a standard, perhaps it will allow a smaller egc for the 1 amp fuse.
Thank you Marty. The wiring supplies actuators and sensors on skid-mounted controls equipment. I would normally follow NFPA 79 for this application but 79 specifically states it is not applicable in hazardous locations so I am back to NFPA 70. Specifically, the wiring to the transmitters is via CCW cable with a #16 AWG twisted pair and a #16 drain wire. I want to use the drain wire to ground the transmitter because I don't have any other conductors. This situation prompted my other question as to whether the sheathing of the CCW cable can act as the equipment grounding conductor because if it can I don't need to be concerned with the drain wire's size.
I know this question is almost a year old, but did you ever find a suitable answer?
If you run DI signal wires (#14 or smaller) into a hazardous location with underground PVC conduit, what is the minimum EGC required? I agree with the interpretation that #14 is the minimum and if you are larger than #14 the EGC is not required to be smaller than the circuit conductors, but I don't deal much with 24VDC signal conduit and I would prefer to not waste copper.
As long as you follow the wiring and equipment rules in the applicable hazardous location article, I'm not aware of a rule that would require any additional grounding. Normally, a class 2 circuit, 50 volts or less, is not required to be grounded at all.
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