Loadcenter with 4 pole main circuit breaker?

Status
Not open for further replies.
O

olc

Senior Member
A building with two tenant loadcenters. Identical 30 space with 150A 4 pole main circuit breakers except one has the 4 switches connected and on does not.
I am not sure what is going on. What are the 4 poles connected to?


(I did not open and it is not convenient to go back to look.)
 
G

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
olc said:
A building with two tenant loadcenters. Identical 30 space with 150A 4 pole main circuit breakers except one has the 4 switches connected and on does not.
I am not sure what is going on. What are the 4 poles connected to?


(I did not open and it is not convenient to go back to look.)
Click to expand...

Wow.
That could be three phase four wire which allows for either delta or wye loads and single phase line to line and line to neutral loads. But it is not normal practice to fuse or switch the neutral, so that would be strange and probably not compliant with current codes. If the neutral is switched, then the handle tie is required to prevent you from opening the neutral while leaving any of the phase wires hot.

Or it could be two-phase five wire, with four phase lines at 90 degrees to each other, with or without an un-switched neutral. That would be extremely rare and antique, and most likely in the downtown area of a large, old city.

Or it could be fed with two parallel 150A conductors on each phase landing on separate poles and just be plain ordinary 120/240 single phase three-wire. But I would ask why it is being fed with double 150A main breakers instead of something larger. Can the panel really take 300A on the bus?

From those choices, I favor the third one, but more information is needed. In particular, how many insulated buses are in the panel.
 
Smart $

Smart $

Esteemed Member
Location
Ohio
olc said:
A building with two tenant loadcenters. Identical 30 space with 150A 4 pole main circuit breakers except one has the 4 switches connected and on does not.
I am not sure what is going on. What are the 4 poles connected to?


(I did not open and it is not convenient to go back to look.)
Click to expand...
They are just paralleled circuit breakers. 2 poles for each line.

(If you didn't open, how do you know one had the 4 switches connected and the other did not?)
 
Jraef

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
Riograndeelectric said:
It may not be a 4 pole breaker but a 2 pole as pictured below.
coild be the 2nd load center is missing the tie handle.


Click to expand...

Smart $ said:
They are just paralleled circuit breakers. 2 poles for each line.

(If you didn't open, how do you know one had the 4 switches connected and the other did not?)
Click to expand...

If you are not in North America, it may actually be a requirement, based on the type of Earthing System you have. But here, it's more likely the 2 x 2-pole parallel breakers for a main situation.

It's done by the panel and breaker mfrs to "cheat" a size limit on the type of breaker frame that can be used in a particular panel design. Perfectly legal, it's just that the panel mfr did not originally design the panel to handle breakers larger than 100A. So when they later increased the main bus rating, they had to come up with a way to give you a 150A or 200A breaker designed to fit in a mechanical design that only allowed 100A frame devices.
 
O

olc

Senior Member
Sorry - forgot to mention.
The building service is 240V 1 phase.

The "main" breaker does look like the picture above.
 
C

cdslotz

Senior Member
I rebuilt my home service two years ago.
I bought GE because at that time, only GE and Siemens (I think) had 2-pole afci breakers, which I needed due to MWBC's.
I went to Home Depot to buy a 200A, weatherproof panel, but they had those cheap looking 4P, 200A main breakers.
So I ordered through a friend at Rexell thinking I would get a real main breaker with a single handle.........no..it was a 4P 200A breaker just like pictured above.

cheap...
 
Status
Not open for further replies.
Top