I have a job where the heat trace cable for some water piping and a convenience outlet have a seperate disconnect from the rest of the HVAC unit.
It is 115VAC running from the residence on a 20 amp circuit. This enters our disconnect which is a 230VAC 30A non fused disconnect. From the bottom of this disconnect the conductors run to a terminal block and then split off into two circuits. One for the heat and one for the outlet. Each is individually fused.
The question I have is whether I should open only the ungrounded conductor per 380-2(b), or open both per the exception to that rule? Both conductors if ran through the two poles of the disconnect would be broken at the same time.
I am a proponent of breaking both lines since the heat tape is wrapped around water lines (3" copper, or black steel at the pumps), but others at my company do not think the exception should apply.
I would appreciate any knowledge that could be offered.
radSS, I agree that what you propose is perfectly code compliant.
Regardless of what you are installing the code requires a disconnect that "shall" disconnect all the ungrounded conductors, that in no way prevents you from disconnecting all the conductors at the same time.
As a matter of fact the disconnection of the grounded conductor is actually required when dealing with fuel pumps. 2002 514.11(A)
In your case I do not see the need to disconnect the grounded conductor but you certainly can if you want.
If this heat trace was cord and plug connected the grounded and grounding conductors are all disconnected simultaneously, doing the same with a switch is fine.
Bob Badger Construction & Maintenance Electrician Massachusetts