Connect 100A sub-panel to 200A Main panel

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Joe Cool

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Hello and good day

I've installed a Sq D 200A, 30 space main panel a few years ago.
I would like to connect a sub-panel next to the 200A panel.

I have a brand new Sq D 100A w/Main Breaker, 30 space panel still in the box.
Can I use this 100A panel as my sub panel?

Can I tap off the main lugs in the 200A panel and feed the 100A Main Breaker
in the 100 amp panel? Or would I have to add a 100A breaker
in the 200A panel to feed 100A panel??

Thank you for your time
 
How would you be connecting the 100 amp conductors to the existing 200 amp panel?
 
infinity said:
How would you be connecting the 100 amp conductors to the existing 200 amp panel?
Click to expand...

Thanks much for reply

I would replace the main lugs in the 200A panel with tandem lugs
and feed my 100A panel from there.

Does that sound okay?

Would appreciate any suggestions or code reference.

Thank much!
 
Joe Cool said:
Thanks much for reply

I would replace the main lugs in the 200A panel with tandem lugs
and feed my 100A panel from there.

Does that sound okay?

Would appreciate any suggestions or code reference.

Thank much!
Click to expand...

I forgot to mention that my main disconnect is outside the house.
So the 200A panel in the basement has no main breaker only main lugs.
 
Joe Cool said:
Can I tap off the main lugs in the 200A panel and feed the 100A Main Breaker
in the 100 amp panel?
Click to expand...
It's highly unlikely that each main lug will have instructions that allow two conductors in a single hole. So unlikely that you will have to document it with manufacturer instructions allowing it. -- Never mind, Joe. I was slow to post.
 
Joe Cool said:
I forgot to mention that my main disconnect is outside the house.
So the 200A panel in the basement has no main breaker only main lugs.
Click to expand...

Technically the 200 amp panel is a sub-panel not the service.

Since your new sub-panel has a main you could set it up by tapping the 200 amp feeder conductors and applying the feeder rules in Article 240. Finding the lugs to change out might be problematic.
 
Joe Cool said:
Thanks for reply

Is that still required, even though the sub-panel already
has it's own 100A main breaker installed?

Why would I need two 100A breakers connected in series?
Click to expand...

You don't.

Get some polaris connectors and splice in the feeder to the new panel on the line side of the existing panel.
 
infinity said:
Technically the 200 amp panel is a sub-panel not the service.

Since your new sub-panel has a main you could set it up by tapping the 200 amp feeder conductors and applying the feeder rules in Article 240. Finding the lugs to change out might be problematic.
Click to expand...

Thanks Much!

Was hoping that would be okay.
I didn't realize the tandem lugs would be difficult to find.
I've had to install tandem lugs for a sub panel in industrial buildings,
but I didn't have to buy the supplies.
I suppose they would have to be SQ D lugs, as is the panel.
 
Joe Cool said:
Thanks Much!

Was hoping that would be okay.
I didn't realize the tandem lugs would be difficult to find.
I've had to install tandem lugs for a sub panel in industrial buildings,
but I didn't have to buy the supplies.
I suppose they would have to be SQ D lugs, as is the panel.
Click to expand...

I love the tap rules, but it is probably just easier to install a 100 amp breaker. One other option is to install a molded case terminal block - it's just a set of lugs that stabs onto the bus like a breaker. I dont know if square d makes one, but most manufacturers do. Might be a bit cheaper than a 2100 breaker but kinda splitting hairs.
 
Joe Cool said:
Thanks Much!

Was hoping that would be okay.
I didn't realize the tandem lugs would be difficult to find.
I've had to install tandem lugs for a sub panel in industrial buildings,
but I didn't have to buy the supplies.
I suppose they would have to be SQ D lugs, as is the panel.
Click to expand...

Finding a double lug for a residential panel could be difficult, as you said in commercial equipment we change them all of the time.
 
If this type of lug would be a violation,
would you recommend using the Polaris type connectors
that someone mentioned earlier?

IMG_0179A.jpg
 
There are two problems with those lugs. First is whether they physically fit in a resi loadcenter. Second is you could get called in a 110.3 (b) for modifying equipment with parts that aren't approved by the manufacturer (fwiw I feel very strongly that I can swap and use listed lugs, but an inspector might feel differently). Imo using Polaris connectors will cost more in time and money than just using a 100 aMP breaker
 
electrofelon said:
There are two problems with those lugs. First is whether they physically fit in a resi loadcenter. Second is you could get called in a 110.3 (b) for modifying equipment with parts that aren't approved by the manufacturer (fwiw I feel very strongly that I can swap and use listed lugs, but an inspector might feel differently). Imo using Polaris connectors will cost more in time and money than just using a 100 aMP breaker
Click to expand...

I think you R probably right....

So then I will have a 100A QO breaker in the 200A panel
feeding the 100A main breaker in the sub panel.

If that's okay, then that's the way I'll do it
Thanks much
 
My own panel is set with the large lugs at both ends of the breaker strips so you can feed it from either end. I have an adapter at one end for a main breaker, but that did not come on it, I had to buy it separate. So, if your is the same, what would stop you from running the feed for the 100amp from the bottom set of lugs? Or is there a code stopping that? I myself was thinking of getting a second adapter on mine to place a feed breaker there so I can have breakers or disconnects on both ends of the feeder... not sure it is necessary, but it is a feel better for me..lol.
 
Adamjamma said:
My own panel is set with the large lugs at both ends of the breaker strips so you can feed it from either end. I have an adapter at one end for a main breaker, but that did not come on it, I had to buy it separate. So, if your is the same, what would stop you from running the feed for the 100amp from the bottom set of lugs? Or is there a code stopping that? I myself was thinking of getting a second adapter on mine to place a feed breaker there so I can have breakers or disconnects on both ends of the feeder... not sure it is necessary, but it is a feel better for me..lol.
Click to expand...

Those are called feed thru lugs. Pretty common on commercial panelboards, but usually not available on resi "loadcenters" here. Meter mains usually have them.
 
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