120-240V device on bi-phase service?

[derekleffew]

So I'm looking at this device:

Doug Fleenor Design - DMX1REL20A
It's just a switch--it doesn't care what you put into it, it will turn whatever goes in ON or OFF.

A portion of the specs:

Power input: 120 - 240 volts, 50/60 hertz, 2 watts (plus load).
Power input plug: NEMA type 5-15P dead front plug standard, others optional.
Power output: Input power is switched to output. (Hot side only)
Power output socket: NEMA type 5-15R dead front receptacle standard, others optional.
Output rating: 15 amps with standard connectors, 20 amps with optional connectors.

BOLD added by me.

I've used it before (though I can't remember for what [I've also rented one with NEMA 5-15 s for control of a hazer]), and it came from the rental house with L6-20 I/O connectors. Correctly, as we were using it on a 208V line. I didn't realize until just now that it was only switching ONE of the two hot legs. Is this, or could this, be a problem?

A related scenario:
When using any auto-ranging 90-250V device, the power switch probably only interrupts the hot wire. So when connected to bi-phase, the "neutral" is ALWAYS 120V potential difference to ground. Cause for concern? Should power switches on ALL auto-ranging devices also switch the neutral, just in case?



(Standard QotD rules apply: Students ONLY, for one week from date of posting.)

 

[sww1235]

I would think that switching only one of two hot legs would be dangerous, because there is 120V potential to ground with either 208V or 240V line. I would say that if a power switch is switching only the hot leg on 120V single phase service, that is all it should be used for. If there is a potential for multi voltage use, than both conductors should be switched and fused.

On a side note, most industrial switches, will switch all wires except ground, so this has precedent

Also how are the control electronics in the DMX relay powered? Does it need a neutral connection? Does it have an auto-ranging power supply?

 

[epimetheus]

On a side note, most industrial switches, will switch all wires except ground, so this has precedent

No, this is a large generalization and not accurate. Many 3 phase disconnect switches and circuit breakers do not switch the neutral, only the phases. Sure, you can wire the 2 phases and the neutral of a 120/240V single phase service to a 3 pole disconnect or breaker, but this is not a code requirement except in certain situations.

 

[sww1235]

No, this is a large generalization and not accurate. Many 3 phase disconnect switches and circuit breakers do not switch the neutral, only the phases. Sure, you can wire the 2 phases and the neutral of a 120/240V single phase service to a 3 pole disconnect or breaker, but this is not a code requirement except in certain situations.

Sorry, I should not have generalized. I meant that it was not against code