120V Panel

[engy]

Is it OK to make a "120V only" panel by feeding both phases of a single-phase 3-wire panel from the same 120V wire?
I have a 120V UPS that needs to feed a panel, and I need to provide an external bypass so the UPS can be fully isolated.
I don't think this violates any code, but would obviously look a little funny at first. (a little signage seems appropriate)
Some have mentioned 110.3B, but that is pretty darned thin...

I have been away from the forum for a while, good to see the single-phase vs two-phase debate is back:lol::lol::lol::lol::happysad:

 

[Dennis Alwon]

IMO, it is compliant and I have done it in the past.

 

[Speedskater]

From the Middle Atlantic paper on AC power and large Audio/Video systems using isolation transformers with dual 120V outputs.

There are two main reasons for this; the first is simply
that when it comes to 120/120 it is not always intuitive to think that
the electrical panel board requires a double sized neutral bar. If the panel is not factory-integrated into
the isolation transformer there can be confusion in the field, leading to installation errors and, if indeed
installed incorrectly, can introduce a dangerously undersized neutral bus into the facility.

http://www.middleatlantic.com/pdf/Power Paper Addendum.pdf
http://www.middleatlantic.com/resources/whitepapers.htm

 

[kwired]

the electrical panel board requires a double sized neutral bar.

Or not use the panel to 100% of its rating works also.

100 amp 120/240 panel only being supplied with 50 amps 120 only like described in the OP will only have 100 amp max on the neutral. Next question is are typical neutral assemblies in a 120/240 100 amp panel rated for 100 amps or do they assume there will be a fair amount of balance and neutral will only carry imbalance?

There are panels with 200% neutrals also.

 

[hillbilly1]

The op is stating that both legs in the panel are fed from one wire, this will not require an oversized neutral bar because the maximum imbalance will be 100 amps, not 200. This is a quite common setup. Their can be no shared Branch circuit neutrals though, unless oversized.

 

[kwired]

The op is stating that both legs in the panel are fed from one wire, this will not require an oversized neutral bar because the maximum imbalance will be 100 amps, not 200. This is a quite common setup. Their can be no shared Branch circuit neutrals though, unless oversized.

True, I missed that somehow.