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Tuesday, October 21, 2014
Question:
Re: CQD answer published Friday, Oct 10, 2014
Charlie, a way to avoid the GFCI requirement is to provide a dedicated branch circuit to the appliance and then "hard-wire" it to the circuit by removing the attachment plug cap.
The fly in the ointment is 110.3(b) for the listed appliance being modified by removal of the plug cap. However, one could take the stance that since this is NOT prohibited by the NEC, that it then can be done.
The rational to justify this is for the appliance losing it's grounding conductor connection because of a broken prong of the plug cap, or whatever. With a hard-wired circuit, such as a dishwasher, gas furnace, etc., the chances of the ground being lost and a shock hazard resulting is very low.
Remember that GFCI's fail too. Many, that are not periodically tested, exceed the 1/40th second disconnect time allowing hazardous current to pass for too long a time that could initiate ventricular fibrillation. They're not fool proof and do NOT limit current, just the time the current flows.
There are devices that will provide an alarm, with remote contacts, that are made by companies such as "Goldline". They fit inside a standard switch box, 3-1/2" deep, and work on Class 2, 24 volt 60Hz or DC power. We used to use these powered by an standard class 2 power transformer, for hard wired refrigeration units in laboratories containing temperature (nonexplosive) perishable chemicals, emulsions, etc. An output contact (SPDT) generally went to the building management system to alert someone during off-hour times. The unit was under $100. It also had an optional expander to provide four monitor (SPST) input points.
A simple logic type thermostatic switch was used for the sensor, such as one set 45F. Since it was class 2 wiring, there was no hazard of fire or shock. These inputs were also investigated and found suitable for some flammable liquid applications, and could be used in conjunction with Intrinsic Safety barriers for more hazardous situations. (only the inputs, not the logic device). These designs were all documented by engineering drawings and procedures, which were reviewed by qualified technical engineering personnel. They were also reviewed and accepted by the local AHJ.
Nick Abbatiello
A
Answer:
Hey Nick good to hear from you. I agree with the individual branch circuit as a means for minimizing the chance of other faulty equipment causing the GFCI to operate. But removing the attachment plug and direct wiring the appliance would likely change the manufactures intent of how that appliance was to be connected and also violate 110.3(B) and 400.7.
110.3(B), 400.7