# allowable number of 200A panels from a 400A disconnect



## SUNNYSPIDER (Jul 19, 2011)

I am trying to determine where in the code to look to find rules regarding the number and size restrictions on panels fed from a 400A fused disconnect. I'd like to add 4-200A panels (subpanels). The load side lugs in the disconnect are rated for multiple wires, and an ample sized wireway is installed beneath the location of the possible panel additions. I'd like to bring 2 either 250 or 350MCM feeder sets to two sets of Burndy lugs and then tap two 200A panels from each. 

My questions are: Can I even load the 400A fused disconnect with 4-200A panels, and if so are the feeders going to be too small to tap twice with my wire selection from above? There has to be a way to do this, even if it involves adding a terminal box which I can run parallel feeds to, and from there I can run feeders to 4 different panelboards. The overall service calculation is well under the 400A available. Thanks!


----------



## BBQ (Nov 16, 2010)

7,987,486 ......... in other words you can add as many panels to the 400 amp switch as you want as long as the total calculated load remains under 400 amps.

Keep in mind you cannot 'tap a tap' so each 200 amp conductor has to run back to a 400 amp conductor or all the way back to the disconnect.


----------



## guest (Feb 21, 2009)

BBQ said:


> *7,987,486 ......... in other words you can add as many panels to the 400 amp switch as you want* as long as the total calculated load remains under 400 amps.
> Keep in mind you cannot 'tap a tap' so each 200 amp conductor has to run back to a 400 amp conductor or all the way back to the disconnect.



Now that was funny..and true. 

Bob, what is the highest number of panels off of one main you've ever seen in the real world?


----------



## SUNNYSPIDER (Jul 19, 2011)

*Ha ha!*

Thanks for your posts. Now I just have to find the right lugs. Due to wireway fill - tapping is out, I need to get all four sets of 250's back to the 400A disconnect. Any advice? (40 yr. old disconnect)...


----------



## SUNNYSPIDER (Jul 19, 2011)

*Pics to help*

Here are some pics of the disconnect - I would expect a nut in order to detach the current lug and attach new 4 port lugs, but it doesn't look like that exists... has anyone replaced similar lugs before? What did you use?


----------



## kwired (Dec 20, 2009)

SUNNYSPIDER said:


> Thanks for your posts. Now I just have to find the right lugs. Due to wireway fill - tapping is out, I need to get all four sets of 250's back to the 400A disconnect. Any advice? (40 yr. old disconnect)...


Why don't you have room in wireway? Don't try to put all the taps in the same cross section. Conductors can only fill wireway 20% that leaves a lot of space for taps.


----------



## SUNNYSPIDER (Jul 19, 2011)

*reply to kwired*

I guess my understanding is that you take the sum of the cross section of all wires in the wireway at any point along the wireway - I would need to parallel runs of 250 AL to a 6 port Burndy and then a tap to each of the 4 200A panels. This is 18 250's - using XHHW brings that total to 7.15 sq. inches or so, and is without ground wire or bonding wire. Wireway is 6x6 - 20 percent is 7.2, I may also need to add some 12 AWG for a number of heat circuits etc.?


----------



## A Little Short (Nov 11, 2010)

SUNNYSPIDER said:


> Thanks for your posts. Now I just have to find the right lugs. Due to wireway fill - tapping is out, I need to get all four sets of 250's back to the 400A disconnect. Any advice? (40 yr. old disconnect)...


Without seeing the disconnect, I'm not sure you can feed 2 panels from it. But if you check and it can, just feed two 200 A panels, then run a feeder to a sub panel from each 200 A main. Can you replace the 400 A disc. with a 400 A meter base and then you can run 2-200 A panels from there as long as they are in the same building, then feed the subs, 1 from each 200 A main.

Edit: you posted your pics before I posted this. Are those the lugs that came with the disc.?


----------



## SUNNYSPIDER (Jul 19, 2011)

Pics are attached above. Can't change the disconnect. If I am using the wireway fill rules wrong and fill calcs. are for any given cross section, then I'm probly fine.


----------



## SUNNYSPIDER (Jul 19, 2011)

*Not sure where/how to land 1/0 ground*

Can anyone help me with where to land my 1/0 gnd to? I ran a 1/0 through the wireway and tapped it 4 times with #4 to each of my 4 200 Sub panels. But I'm not sure where I need to land it in the 400A disconnect.? - see pictures in a previous thread. For now I split bolted it to the ground that came in with the service conductors because that wire will actually fit under the lugs provided to bond the neutral to ground. Can I add a lug to the cabinet and land it there instead or do I need to replace the Main Bonding Jumper lug? Also, I need to run a 1/0 gnd to the two 85 gal. water heaters - where will that be permitted to land? I'd like to add a two space lug to the cabinet and land both 1/0's to it and call it good, but my concern is that, other than a #6 jumper from the main bonding jumper lug to a bond bushing on the service entrance conductor conduit, the 1/0's I am adding will be isolated from the main bonding jumper.


----------

