Panelboard top vs bottom feed (Siemens)

Of course the answer may differ between manufacturers, but what is the difference between top and bottom feed? I typically use Siemens for my 250-1000 amp panelboards and a line in the part numbers indicates top or bottom feed. Is there a difference? The cabinet mounting studs are symmetrical, so I dont see how it could be a wire bending space thing. There isnt any lettering or lebeling that would be upside down, other than what is on the breakers. I have thought about this when putting the panelboard into the cabinet and can never see anything that would be different or matter if I just installed it the other way.....?
 

mopowr steve

Senior Member
Location
NW Ohio
Besides the main breaker either being positioned at the top or bottom of panel by how you order it. If you turned a top fed main breaker panelboard up-side-down the breaker handle would be in the wrong position. For main lug only that may not be a problem.
 
Besides the main breaker either being positioned at the top or bottom of panel by how you order it.
Every panel board I have procured comes with the guts in a separate box than the cabinet, and the cabinet mounting studs are symmetrical so it can go either way.

If you turned a top fed main breaker panelboard up-side-down the breaker handle would be in the wrong position. For main lug only that may not be a problem.
I think you have it here. I forgot about the "when vertical up is on rule" 240.81. You know, I don't think I have ever installed a PB with a vertical main breaker. Usually I am dealing with MLO PB's , and the few with MB I have done had a horizontal handle throw.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Besides the main breaker either being positioned at the top or bottom of panel by how you order it. If you turned a top fed main breaker panelboard up-side-down the breaker handle would be in the wrong position. For main lug only that may not be a problem.
That is why many main breaker panels have the main breaker installed so it operates horizontally and not vertically. If you have a vertical operation main breaker, sometimes there are instructions that permit you to flip the breaker itself so when you flip the guts the breaker operation is still in compliance with the up = on rule.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Besides the main breaker either being positioned at the top or bottom of panel by how you order it. If you turned a top fed main breaker panelboard up-side-down the breaker handle would be in the wrong position. For main lug only that may not be a problem.
We just unbolt it and flip the main over.
 

Carultch

Senior Member
Location
Massachusetts
Here are several reasons why it might not be as simple as "just turn it upside down".
1. Aforementioned reason of the main breaker possibly no longer having ON in the top position.
2. If it is in a NEMA3R enclosure, the enclosure can only be oriented with the intended top side up, for proper drainage. The interior may only fit in it in one orientation.
3. Factory-applied warning labeling may no longer be oriented to be legible.

Ideally, the manufacturers would make all panelboards field-configurable regarding top fed vs bottom fed, but it is rare that you will know in advance that there is no subtle difference preventing you from field-configuring.
 
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