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#220311 09/28/19 11:54 AM
Joined: Apr 2002
Posts: 189
T
triple Offline OP
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What are the limits (if any) of switching a 2-pole load with only one of its poles? Perhaps, if it is an automatic control then it is ok but if it is manual then it is not allowed? Also, does it matter if the single pole switching device is on the unit or in a remote location? For example, a 240v baseboard, electric heater may have a single pole, line-voltage thermostat (either on the heater itself or on the wall). However, take a 208 or 240v, single phase pole-light. Can I control it by a single-pole photocell on a nearby building (no 2-pole contactor or relay in between)? If so, why could I not also have a manual override switch that breaks only one line? Understand that I personally would not do either of these things and consider it "bad practice" whether it is code-compliant or not. Also, anything requiring an actual disconnect would need the breaking of all phase conductors but that is not a case I am considering.

2017 / 2014 NEC & Related Books and Study Guides
Joined: Jul 2004
Posts: 9,669
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G
Member
The way I read it you can use a single pole device for control but you still need a 2 pole device for a disconnect anywhere one is required or anything labeled "off".


Greg Fretwell
Joined: Apr 2002
Posts: 189
T
triple Offline OP
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Good point. I didn't think of the fact that the switch may (but not necessarily) state "off" on it. For instance, a decorative style switch would not and there could not be many circumstances where a pole light requires a disconnect. It still seems as though the code has dropped the ball if a s.p. decora switch is allowed here.

Joined: Jul 2004
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G
Member
I think the exception is more limited than simply allowing anything to be OK. These are in individual articles on specific pieces of equipment like 424.20(B)

Quote

(B) Thermostats That Do Not Directly Interrupt All Ungrounded
Conductors. Thermostats that do not directly interrupt all
ungrounded conductors and thermostats that operate remotecontrol
circuits shall not be required to meet the requirements
of 424.20(A). These devices shall not be permitted as the
disconnecting means.



Greg Fretwell
Joined: Jul 2004
Posts: 9,669
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G
Member
Your single pole switch to a lamp is outlawed here

Quote
410.93 Double-Pole Switched Lampholders. Where supplied
by the ungrounded conductors of a circuit, the switching
device of lampholders of the switched type shall simultaneously
disconnect both conductors of the circuit.




Greg Fretwell

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