(2) 225A Breakers feeding (1) 400A Fused Disc?

[PSU Electrical]

My mind is wondering with this one so bear with me:

I have a client doing a retrofit on a loading dock facility. The loading dock has an old Square D, 600A panelboard with practically no load on it, feed from a MDP a few hundred feet away. Of course, like every other client, they have no money and it needs to be done yesterday. Anways, they are in the process of putting a large APC Server in the office of this building that the other Engineering firm is demanding a 400A, 3-phase, 480V feed to the server. The 600A panelboard can only accept 225A breakers. I can not figure out a way to provide a 400A CB or Fused Disconnect to this server since the panelboard can only accept 225A breakers. So, my question is can (2) 225A CB's feed (1) 400A Fused Diconnect, then to the server? I would never suggest designing something like this but retrofits are terrible. The Electrician tells me there no real way to tap the 600A bus to add a 400A CB to it so that would leave me to think I either need to get a 400A feed from another building (very far away) or replace the 600A panel with a new 800A to accept 400A CB's. Any other suggestions?

 

[kwired]

Tap the feeder to the panel in question if you do not want to replace it. May be easier said than done but is a suggestion.

 

[infinity]

Can you tap the 600 amp bus and feed a 400 amp disconnect switch adjacent to the MDP? A parallel set of #3/0's or one set of 600 kcmil should work.

 

[augie47]

and, if needed, the Code reference as to why you can't use the two breakers is 240.8.

 

[PSU Electrical]

240.8 is what I was looking for; I knew (2) parallel CB's wouldn't fly.

The challenge the EC is dealing with is just the phsycallity of doing so. My first thought was to tap the bus and he tell me there isn't a lot of room, 2nd thought was the feeder. Thanks for the feedback.

 

[david]

Before running a second feeder from another building I would look at 225.30

 

[kwired]

Before running a second feeder from another building I would look at 225.30

I don't believe he mentioned if this was a feeder to a separate building.

He can only have one feeder to the separate building if that is what he has but 225.33 does allow that one feeder to supply up to six disconnecting means grouped at same location.

 

[david]

I don't believe he mentioned if this was a feeder to a separate building.

Post #1 "I either need to get a 400A feed from another building (very far away) or replace the 600A panel with a new 800A to accept 400A CB's. Any other suggestions? ."

Since he talked of a 600 amp panel and then mentioned another building far away i took this to mean he was thinking of suppling this with a secound feeder.

 

[Cow]

Like everyone else said, it sounds like you have two options:

1. Tap the feeder for the added 400A disco.
2. Replace the 600A panel with a 400A unit with feed through lugs. This would allow you to feed the few existing loads you have as well as the new server.

 

[dkidd]

So, my question is can (2) 225A CB's feed (1) 400A Fused Diconnect, then to the server?

You can't connect two breakers in parallel.

Tapping the bus would need the AHJs permission.

 

[Fishspark]

Fix It

Fix It

400 amps sounds like a lot of power for that.?
Out with the old & in with what will work.. Done !
no money and no time - not your problem.

 

[Smart $]

...

Tapping the bus would need the AHJs permission.

No permission req'd if the panel is designed for the buses to be tapped (e.g. using a feed-thru lug kit labeled for the panelboard). AHJ "approval" [as distinguished from "permission"] is always req'd ...

 

[Little Bill]

No permission req'd if the panel is designed for the buses to be tapped (e.g. using a feed-thru lug kit labeled for the panelboard). AHJ "approval" [as distinguished from "permission"] is always req'd ...

Are you saying "forgiveness is easier to get then permission"?

 

[dkidd]

No permission req'd if the panel is designed for the buses to be tapped (e.g. using a feed-thru lug kit labeled for the panelboard). AHJ "approval" [as distinguished from "permission"] is always req'd ...

Installing a manufacturers's designed UL listed lug kit is not the same as tapping the bus.

 

[kwired]

Installing a manufacturers's designed UL listed lug kit is not the same as tapping the bus.

If the conductor being supplied is less ampacity than the overcurrent device supplying the panel it is a tap no matter how it is connected. If the conductor is same or higher ampacity than the overcurrent device it is simply an extension of the feeder.

 

[Smart $]

Are you saying "forgiveness is easier to get then permission"?

Though it may be, I'm saying AHJ approval is Code req'd, AHJ permission is not...

...but if the AHJ is asked and permission is granted beforehand, get it documented.

 

[Smart $]

Installing a manufacturers's designed UL listed lug kit is not the same as tapping the bus.

Aside from what kwired said, the AHJ may have the authority to permit you to do something questionable, but consider AHJ permission is no substitute for a UL listing. Altering a listed panelboard by doing something not consistent with its listing will render its listing void. Doing such puts unnecessary liability on the EC.

 

[jim dungar]

Square D makes plug-on lug kits that are the same size as a 200A breaker. You could use two of these plus a rule from 240.21(B), to feed your 400A switch, as long as the 600A is not already being fed using a tap rule.

 

[augie47]

Square D makes plug-on lug kits that are the same size as a 200A breaker. You could use two of these plus a rule from 240.21(B), to feed your 400A switch, as long as the 600A is not already being fed using a tap rule.

good thought

 

[Smart $]

Square D makes plug-on lug kits that are the same size as a 200A breaker. You could use two of these plus a rule from 240.21(B), to feed your 400A switch, as long as the 600A is not already being fed using a tap rule.

As long as the panelboard is MCB it would not matter if fed by tap... you can tap the load side of a single OCP at the end of a tap.