Use Definite Purpose Contactor To Switch Different Voltages To LED High Bay

[dng]

Hi --

We're having an LED high-bay fixture installed that will operate on voltages from 110 to 277. The lighting in this particular area is wired for 120 volts, and is normally switched off at the end of the day.

The stand-by emergency power available to us is supplied at 277 volts (which is what most of the fluorescent fixtures in our facility use).

We'd like to have this fixture wired into the stand-by system. Is it legal to use a definite-purpose contactor to switch between the two different voltages, i.e., when the coil on the contactor is energized, the fixture receives 120, but with power-loss to the coil, to fixture receives 277?

Any help is appreciated -- Cheers
[h=1][/h]

 

[jumper]

I do not know the answer, never encountered this situation, but I am not liking this solution.

 

[petersonra]

I do not know the answer, never encountered this situation, but I am not liking this solution.

I don't see any major issue with it. I'd want to switch out the hot and neutral leads so you do not accidentally connect the neutral from one system to the neutral of the other.

Use an IEC style contactor that has the contacts mechanically linked so if you get a welded contact the whole contactor will still switch or not switch.

Whether it is a code legal solution is something else.

 

[jumper]

I don't see any major issue with it. I'd want to switch out the hot and neutral leads so you do not accidentally connect the neutral from one system to the neutral of the other.

Use an IEC style contactor that has the contacts mechanically linked so if you get a welded contact the whole contactor will still switch or not switch.

Whether it is a code legal solution is something else.

You draw it, stamp it and I will install it.

Code legal, safe, or anything else is your problem then as long as I do correctly.

No problem.

Else, no way I can endorse this solution.

 

[hbiss]

Don't know if your LED driver is the same, but with multi-voltage fluorescent ballasts if you power it up with one voltage you can no longer use it on any other.


-Hal

 

[kwired]

Why not reconnect the thing to 277 for normal power?

If neutral is common to other 120 volt loads you should be separating that anyway if you want to run at both voltages, not that it won't "work" it just isn't code compliant.

 

[SceneryDriver]

Why not reconnect the thing to 277 for normal power?

If neutral is common to other 120 volt loads you should be separating that anyway if you want to run at both voltages, not that it won't "work" it just isn't code compliant.

Out of curiosity, what do you believe makes the proposed solution not code compliant? I agree that's probably a poor idea as it will confuse people down the road who have to troubleshoot it, but I'm not sure it's actually not allowed.

As long as both the neutral and phase conductors are switched together, and the switching mechanism is mechanically interlocked (IEC-style reversing contactor, referenced above) it should work.

I've actually done something similar with an line powered, but battery- & inverter-backed special effect a few years ago.



SceneryDriver

 

[dng]

Why not reconnect the thing to 277 for normal power?

If neutral is common to other 120 volt loads you should be separating that anyway if you want to run at both voltages, not that it won't "work" it just isn't code compliant.

Yeah, we actually have considered that as well. We'll just need to be sure that we can separate out that circuit. Thanks for the reply.

 

[dng]

Out of curiosity, what do you believe makes the proposed solution not code compliant? I agree that's probably a poor idea as it will confuse people down the road who have to troubleshoot it, but I'm not sure it's actually not allowed.

As long as both the neutral and phase conductors are switched together, and the switching mechanism is mechanically interlocked (IEC-style reversing contactor, referenced above) it should work.

I've actually done something similar with an line powered, but battery- & inverter-backed special effect a few years ago.



SceneryDriver

Was just hoping for a little advice -- it's definitely unusual and weird. We just want to have some viewpoints before making the spec, mostly to be sure that our explanation is understandable. Thanks for the reply.

 

[petersonra]

Else, no way I can endorse this solution.

What code provision does it violate?

 

[petersonra]

I think this chain of logic precludes doing this.

700.25 Branch Circuit Emergency Lighting Transfer Switch.
Emergency lighting loads supplied by branch circuits rated at
not greater than 20 amperes shall be permitted to be transferred
from the normal branch circuit to an emergency branch
circuit using a listed branch circuit emergency lighting transfer
switch. The mechanically held requirement of 700.5(C) shall
not apply to listed branch circuit emergency lighting transfer
switches.

700.2 Definitions.
Branch Circuit Emergency Lighting Transfer Switch. A device
connected on the load side of a branch circuit overcurrent
protective device that transfers only emergency lighting loads
from the normal supply to an emergency supply.

Informational Note: See ANSI/UL 1008, Transfer Switch Equipment,
for information covering branch circuit emergency lighting
transfer switches

However, I suspect you could buy a device that is not a whole lot more than a contactor to accomplish the same thing as long as it is listed properly.

 

[jumper]

What code provision does it violate?

I did not say it was illegal, I have no clue.

I said I would not do it unless I had CYA for myself, hence the drawing and stamp.

 

[kwired]

Out of curiosity, what do you believe makes the proposed solution not code compliant? I agree that's probably a poor idea as it will confuse people down the road who have to troubleshoot it, but I'm not sure it's actually not allowed.

As long as both the neutral and phase conductors are switched together, and the switching mechanism is mechanically interlocked (IEC-style reversing contactor, referenced above) it should work.

I've actually done something similar with an line powered, but battery- & inverter-backed special effect a few years ago.



SceneryDriver

Outside of any issues in chapter 7, one would need to transfer the neutral when switching, if the "normal" circuit were a MWBC, you would still have problems with transferring neutral.

 

[GoldDigger]

Outside of any issues in chapter 7, one would need to transfer the neutral when switching, if the "normal" circuit were a MWBC, you would still have problems with transferring neutral.

Which is why you can specify and purchase an ATS or MTS with a switched neutral that first interrupts the normal ungrounded conductors, then transfers the neutral, then closes the alternate ungrounded conductors. This keeps you from suffering a voltage divider imbalance during the time the neutral is interrupted. The same sequencing of neutral transfer also happens when transferring back.

 

[kwired]

Which is why you can specify and purchase an ATS or MTS with a switched neutral that first interrupts the normal ungrounded conductors, then transfers the neutral, then closes the alternate ungrounded conductors. This keeps you from suffering a voltage divider imbalance during the time the neutral is interrupted. The same sequencing of neutral transfer also happens when transferring back.

Now we are getting away from what OP initially wanted to do with just a definite purpose contactor though.

 

[Strathead]

Now we are getting away from what OP initially wanted to do with just a definite purpose contactor though.

sort of not, though. If these posts were predicated with No, but you can.... that should make you more comfortable. The simple answer is no you can't use a definite purpose contractor to switch legally required emergency systems, and you can't use legally required emergency power to power lights that aren't part of the legally required emergency systems. I think it is a grey area whether you can power a whole room's lights from the legally required emergency system.

So, all of those "unrelated" posts are actually potential solutions to the problem the OP presented an illegal solution to.

that is what I am thinking anyway.

 

[dng]

sort of not, though. If these posts were predicated with No, but you can.... that should make you more comfortable. The simple answer is no you can't use a definite purpose contractor to switch legally required emergency systems, and you can't use legally required emergency power to power lights that aren't part of the legally required emergency systems. I think it is a grey area whether you can power a whole room's lights from the legally required emergency system.

So, all of those "unrelated" posts are actually potential solutions to the problem the OP presented an illegal solution to.

that is what I am thinking anyway.

Sorry if we're off in the weeds here.

Our facility uses four-pole (2 NO, 2 NC) Square D definite purpose contactors in every zone for emergency egress lighting. In these zones, normal power and emergency power are the same voltage.

In every zone, there is a subset of fluorescents that is required to be on for egress. Under normal operating conditions, all fluorescents are switched, so that zones can be dark (we're in a theatre). The egress subset is powered through the two NO poles of the contactor -- when the contactor line-voltage coil is energized (i.e., building power is present), everything is switchable. When the contactor coil loses power (building power is lost), the subset of fluorescents is fed emergency power via the two NC poles, and stays on until power is restored.

 

[Strathead]

Sorry if we're off in the weeds here.

Our facility uses four-pole (2 NO, 2 NC) Square D definite purpose contactors in every zone for emergency egress lighting. In these zones, normal power and emergency power are the same voltage.

In every zone, there is a subset of fluorescents that is required to be on for egress. Under normal operating conditions, all fluorescents are switched, so that zones can be dark (we're in a theatre). The egress subset is powered through the two NO poles of the contactor -- when the contactor line-voltage coil is energized (i.e., building power is present), everything is switchable. When the contactor coil loses power (building power is lost), the subset of fluorescents is fed emergency power via the two NC poles, and stays on until power is restored.

Please see post #7 Petersonra gets credit. Use of a definite purpose contactor for this purpose is illegal.

 

[Strathead]

Please see post #7 Petersonra gets credit. Use of a definite purpose contactor for this purpose is illegal.

Oh, otherwise, using a listed transfer device that is also listed for both voltages would be legal in reference to any of the codes I know. Well, there are little things, like complying with the additional grounding requirements of over 250 volts to ground in the conduit runs.

 

[rt66electric]

Wouldn't be easier to add another light fixture??

Wouldn't be easier to add another light fixture??

Wouldn't be easier to add another light fixture??