mshields
Senior Member
- Location
- Boston, MA
Can you connect 2 phases of a 3 phase panel two the two hot phases of a 120/240V panel and use it accordingly. Can you do it if you add signage indicating same?
using a 3 phase panel on a 120/240V system
- Thread starter mshields
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petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
It's a pretty common practice because the 120 240 panels are cheaper
kwired
Electron manager
- Location
- NE Nebraska
Did you understand what he asked? I read it as he has a three phase panel but is only wanting to connect two of the three busses to ungrounded conductors.Three phase panels are normally higher priced.
That said I see no code issue.
In fact if you want to use I-line series panels for single phase distribution - you still buy a panel with three phase bus, that is only way they are made AFAIK. For one and two pole breakers you simply only order ones that have bus connectors in the positions you are utilizing. Unlike typical miniature breaker styles, you can still utilize 100% of the breaker mounting space with I-Line, those other panel types you will only be able to use ~2/3 the breaker mounting space and the remaining 1/3 is "dead space"
David Castor
Senior Member
- Location
- Washington, USA
- Occupation
- Electrical Engineer
You might want to check the nameplate ratings on the panelboard. No question it will work, but if the panel is UL-labeled only for three-phase service, I think that would be a basic NEC violation of using equipment outside of its rating. It might be labeled such that you can use it - I don't really know.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
The question is kind of confusing but, IF he wants to use a 208/120 panel on a 240/120 service, I think he is out of luck because the panel is listed for a maximum of 208 V.
ggunn
PE (Electrical), NABCEP certified
- Location
- Austin, TX, USA
- Occupation
- Consulting Electrical Engineer - Photovoltaic Systems
I just looked at my Eaton CH catalog; the three phase panels they show are double listed for 208V and 240V.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
if he is using one of those panels, he should be OK.
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
The question came up a couple months ago about panels for a 120/240 high leg. I spent a little time looking, and I could not find any three phase panels that were NOT suitable for the high leg system.
kwired
Electron manager
- Location
- NE Nebraska
In general said panels are factory built to specifications they were ordered to and have custom label on them. They are built out of same components used to make the 240 volt panels. If you order out of stock they will most likely have labeling for 240 volts. But yes that custom label kind of sort of is limiting you to 208 volts.
kwired
Electron manager
- Location
- NE Nebraska
I kind of have doubts you will find one with such listing or labeling. Sort of no different than only using one or two poles of a three pole breaker. Might not be great economical decision but creates no increased hazard from using it that way either.
Fred B
Senior Member
- Location
- Upstate, NY
- Occupation
- Electrician
In some ways it might be idea in putting a wrench into the handihacks from getting their hands into it. Most know absolutely nothing about 3 phase and with a 3ph only on 1 ph service, having every third space un used would really get them confused.
kwired
Electron manager
- Location
- NE Nebraska
If every third space in the panel is dead they may not get why but they figure out it doesn't work.
If every third space in the panel is a 208 volt high leg, they burn things up when they connect to it, and they still don't get why.
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
I dont think you will find a black and white answer. The only thing that may prohibit it is "manufacturer's instructions" in 110.3(B). Then it would depend on the wording in the instructions/listing and possibly the interpretation of that wording. I.E. if it listed specific voltages and systems and said "for use ONLY on......" and then if it didnt use the word "ONLY" you can play the game if "it doesnt say I cant so I can"
kwired
Electron manager
- Location
- NE Nebraska
Similar but different question - can you connect both busses of a 120/240 single phase panel together somehow and supply the entire panel with 120 volt two wire feed?I dont think you will find a black and white answer. The only thing that may prohibit it is "manufacturer's instructions" in 110.3(B). Then it would depend on the wording in the instructions/listing and possibly the interpretation of that wording. I.E. if it listed specific voltages and systems and said "for use ONLY on......" and then if it didnt use the word "ONLY" you can play the game if "it doesnt say I cant so I can"
ggunn
PE (Electrical), NABCEP certified
- Location
- Austin, TX, USA
- Occupation
- Consulting Electrical Engineer - Photovoltaic Systems
Sure; off gridders with 120V inverters do it.
kwired
Electron manager
- Location
- NE Nebraska
And I've seen it when only a 120 volt feeder is run regardless of the source.
One somewhat common example, 480x120 transformer supplying somewhat limited 120 volt loads, but at least one load is more than half the VA rating of the transformer so you don't really want to connect it as 120/240.
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