I smell something fishy....

Status
Not open for further replies.
B

bcorbin

Senior Member
I am looking over an old one-line diagram here...and I see a bunch of small 120/240V-1ph, 3w electrical panels fed from a larger 208Y/120V panel. Each large panel circuit breaker feeding a small panel is single pole. However, the main circuit breakers of the small panels are all 2-pole. There are also lots of 2-pole branch breakers within the small panels.

I am wondering why someone would have fed those panels with only one 120V hot. While I haven't personally pulled the cover off, I can only imagine all of the 2-pole branch breakers with one hot landed and an empty pole.

Is this code-compliant? I would certainly never design it that way.
 
The arrangement you describe is very typical for large residential multi-family dwellings here, although I'm not quite what you mean about a single 120 volt breaker.
 
bcorbin said:
Each large panel circuit breaker feeding a small panel is single pole.
Click to expand...
Are you sure about that? It may just be drawn that way. Can you eyeball the actual installation?
 
I'm reading the breakers off of a bussing sheet, which clearly indicates the number of poles per breaker.

I'm now being told these are isolation panels (not labeled as such); the application is in a hospital. That makes more sense.
 
bcorbin said:
I'm now being told these are isolation panels (not labeled as such); the application is in a hospital. That makes more sense.
Click to expand...

This is normal practice for feeding Isolation Transformers.

Roger
 
try this

try this

Is it possible that the service used to be a 120/240v delta and somewhere down the line the utility may have changed to a WYE, the 2 pole breakers in the main distribution sounds like many delta's
 
LLSolutions said:
Is it possible that the service used to be a 120/240v delta and somewhere down the line the utility may have changed to a WYE, the 2 pole breakers in the main distribution sounds like many delta's
Click to expand...

The question was answered by Roger. :)

roger said:
This is normal practice for feeding Isolation Transformers.
Click to expand...
 
Status
Not open for further replies.
Top