120-277 Volt Signs

B

batch

Member
Location
Florida
Hi, we manufacture illuminated signs. Most are LED these days. 99% of the time the signs are powered by a 120 volt on a 20 amp breaker.
Occasionally an electrician will connect 277 volt to our sign. Resulting in our power supplies burning up. To prevent this we replaced the 120 volt power supplies with 120-277 volt power supplies.

We install signs for a couple of school districts and one of those county districts sometimes provides a 240 volt circuit. Sometimes with a neutral and sometimes with out a neutral. But, we never really cared because our signs can run anything between 120-277 volt.

We run the internal wiring to a bellbox located on the outside of the sign ta the point that the branch circuit will enter the sign enclosure. This is also the disconnect location. Since we most often encounter 120 volts, we use black, white, and green conductors.

Recently we installed a sign that had an old 240 volt circuit without a neutral. The crew connected the sign and everything functioned correctly. The school board electrical inspector is saying that we can't use black and white for 220 volt. And that we must rewire the sign to use only black or black and red conductors.

The sign is a UL listed sign and it is labeled for 120-277 volt. The power supple is a UL listed component that is listed in the SAM. It has a black and white lead to connect to. How can we wire the sign in a way that would comply with the code regardless of what voltage within the range is supplied?
 
The conductor colors within the listed sign are not covered by the NEC so the inspector is wrong. Every 277 volt ballast I've ever seen has a black and a white conductor.
 
IMHO this is not an NEC code issue but a UL listing issue. You produce a UL listed piece of equipment (the sign) that internally contains UL listed components and wiring.

You need to confirm (your internal engineering) that the LED driver is actually suitable for L-L operation. It might be 'universal voltage' but require one supply terminal be a grounded conductor. If this is the case, then using it on a 208 or 240V L-L circuit is a violation no matter what the wire colors.

You need to confirm (your internal engineering) that the rest of the installation meets the UL requirements for L-L operation, eg. double pole disconnect switches and the like. If your equipment design was intended and listed for L-N operation, then the fact that it happens to work on an L-L circuit may be a violation.

But if you've confirmed everything meets UL requirements for L-L operation and your listing covers L-L operation, then the NEC ends where your equipment starts.
 
So now the inspector finally relented and cited code. We are in the 2020 code cycle. He cited N.E.C. 200.2(A) commenting that "Cannot use white #12 awg for branch circuit.". He also sited N.E.C. 311.14 "Cannot use white #12 awg for branch circuit." Which isn't applicable to my 120-277 signs.

Article 311 Medium Voltage Conductors and Cable​

 
winnie said:
IMHO this is not an NEC code issue but a UL listing issue. You produce a UL listed piece of equipment (the sign) that internally contains UL listed components and wiring.

You need to confirm (your internal engineering) that the LED driver is actually suitable for L-L operation. It might be 'universal voltage' but require one supply terminal be a grounded conductor. If this is the case, then using it on a 208 or 240V L-L circuit is a violation no matter what the wire colors.

You need to confirm (your internal engineering) that the rest of the installation meets the UL requirements for L-L operation, eg. double pole disconnect switches and the like. If your equipment design was intended and listed for L-N operation, then the fact that it happens to work on an L-L circuit may be a violation.

But if you've confirmed everything meets UL requirements for L-L operation and your listing covers L-L operation, then the NEC ends where your equipment starts.
Click to expand...
Double pole switches are required regardless if it’s 120 or 208/240/480. Both conductors must be broken on signs. The reasoning behind it is too many unqualified sign installers breaking the wrong leg, leaving the sign hot even though the switch is off.
 
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