Double-Lugged Main

tonype

Senior Member
Location
New Jersey
Bottom fed panel to main lugs - 100-amp main at top. The main lugs also supply a 2nd panel (right of photo). This panel has another 100-amp main at the top. Questions:

1. Isn't there an adaptor or similar fitting to use in lieu of the 2 cables on 1 lug?
2. The is no other main - doesn't this potentially create an overload condition on the conductors supplying the first panel?


DSCF3590.jpg
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
Bottom fed panel to main lugs - 100-amp main at top. The main lugs also supply a 2nd panel (right of photo). This panel has another 100-amp main at the top. Questions:
What do you mean by "bottom fed"?
1. Isn't there an adaptor or similar fitting to use in lieu of the 2 cables on 1 lug?
You can find lugs that have spots for 2 wires on them.

2. The is no other main - doesn't this potentially create an overload condition on the conductors supplying the first panel?
only if the current exceeds the conductor rating.
Is there somewhere an upstream OCPD?
 
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petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
The conductors from the bottom seem to terminate in a 100 amp breaker, that has no hold down clip, and back feed the panel.
seems that way to me too. thats why i asked what he met by bottom fed. normally I would think that meant there was a main breaker at the bottom. OTOH, it does not look like it is a standard breaker there either. it seems to extend across the whole panel.

It seems to me that the 100A breaker being backfed will limit the current coming out the top lugs. I am having a hard time understanding the question about protecting any conductors.
 

jumper

Senior Member
seems that way to me too. thats why i asked what he met by bottom fed. normally I would think that meant there was a main breaker at the bottom. OTOH, it does not look like it is a standard breaker there either. it seems to extend across the whole panel.

It seems to me that the 100A breaker being backfed will limit the current coming out the top lugs. I am having a hard time understanding the question about protecting any conductors.
You are right that breaker does seem to extend across. My guess is that wood make it 200 amps. I think Siemens makes breakers like that.
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
Engineer
seems that way to me too. thats why i asked what he met by bottom fed. normally I would think that meant there was a main breaker at the bottom. OTOH, it does not look like it is a standard breaker there either. it seems to extend across the whole panel.
That panel is more than 30years old. Most of the branch breaker do not appear to have the visible trip indicators (Visi-Trip) which was introduced in the mid-60's.

The 100A breaker is a Q1 style which was '2-breakers' wide (high ampacity, >70A, QO breakers were not available until the 80's).
 

hillbilly1

Senior Member
Location
Atlanta,Ga
You are right that breaker does seem to extend across. My guess is that wood make it 200 amps. I think Siemens makes breakers like that.
I've seen Square D use these as a heavierduty type that utilizes the full stab on the buss, it looks like on the handle it's a 125 amp.
I think what the OP is asking about conductor OCP is actually the buss OCP, since this is a backfeed main, and it is highly unlikely the lugs at the top are rated for two conductors, so theres a violation. If I remember correctly, that main is just plugged in across the buss, and does not have a mechanical means of locking it to the buss, which would be violation #2.
 

augie47

Moderator
Staff member
Location
Tennessee
I'm in agreement with Jim and others... appears to be a "backfed" panel with a 100 or 125 amp factory main. With age of the panel, its possible no retaining ckip was required at the time of installation.
It's an ideal situation for some upgrading, but in regard to the top lugs, I'm surprised both conductors fit without some "trimming'.
Barring an upgrade, if the conductors have the amapacity of the main, you might add some polaris connectors and bring one conductor from the lug to two additional in the polaris although that may lead to one of the somewhat rare cases of violating 312.8.
 

iwire

Moderator
Staff member
Location
Massachusetts
Remove it all, start again.




FWIW I doubt that neutral bar was provided with spots for all those large neutrals as well so more modifications there as well.
 

templdl

Senior Member
Location
Wisconsin
See post#8:)
Darned, I missed your post when I reviewed the posts hillbilly1.
I think that you and I concur that it's a code violation that should be corrected first.
I'm not aware of a lug that allows for 2 current carrying conductors to be terminated in only one opening except with the smaller plug on breakers for load centers.
 

kwired

Electron manager
Location
NE Nebraska
You are right that breaker does seem to extend across. My guess is that wood make it 200 amps. I think Siemens makes breakers like that.
That was normal for that vintage of 70 amp and higher breaker for that panel. Sometime in the 80's they figured out how to make them more compact and no longer made those extra wide units that took four branch spaces when installed. They do not have lugs large enough to accept a 200 amp conductor.

If there is a hold down clip installed it would not be visible in the photo, camera angle needs to be more to the left for it to be visible - it was a gold colored metal plate that clamped the mounting feet to the rail so the breaker could not be removed without loosening the plate first.

There were lugs available that were designed to add to the neutral bus for larger conductor termination but that is not what has been used here.

The main lugs (or subfeed lugs) would not have been designed for termination of more than one conductor.
 
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