Multiple panels from 1 service disconnect

[Jawrenn18]

Good afternoon,
I'm in a bind on a project. 800 amp single phase home. 9000 sqft heated and cooled. We were supposed to be installing an 800 amp transfer switch in an assembly with 800 amp main breaker and 4 200 amp breakers. I was notified that the enclosure would not be available until late this year. I got with my supplier and he recommended installing 1 800 amp disconnect, feeding each 200 amp panel from it and installing main breakers in the panels. I've looked at code 408.36 and it seems that this would be permissible. 408.36 references 230.71which states not more than 6 disconnects on the building. I've done this on a few commercial projects with no issue. Just making sure this isn't going to bite me in the behind come final inspection time. The inspectors for this job show up in packs of 3-5 and bring their code books.

 

[hillbilly1]

The six switch rule does not apply here, you have only one service disconnect, the 800. You can have as many 200 amp disconnects you want after that. Length of your taps is what will limit you.

 

[augie47]

The six switch rule does not apply here, you have only one service disconnect, the 800. You can have as many 200 amp disconnects you want after that. Length of your taps is what will limit you.

Agree..that's the key question

 

[Jawrenn18]

Longest run from disconnect to panel is approx 70 feet so I'm over the tap rule. Does 408.36 not allow me to run my service cable for 200 amps and install a main breaker in the panel for overcurrent protection? I realize that's not protecting the service cable but it does protect the panel board per the code in 408. I don't see a length limit in the 408 section. Or is this 2 completely seperate issues? Panel board and Feeder. I'm realizing that my SER from disconnect to panel is not technically a "service feeder" after first disconnect.
I reference the number of disconnect rule to lead to another question. What if I had 7 panels? Would I have to feed one from taps in another panel?
These are the finer points I find myself getting stuck on.

 

[roger]

I reference the number of disconnect rule to lead to another question. What if I had 7 panels? Would I have to feed one from taps in another panel?
These are the finer points I find myself getting stuck on.

You already have a service disconnect per your first post so there is no limit on the number of panels downstream.

 

[don_resqcapt19]

Longest run from disconnect to panel is approx 70 feet so I'm over the tap rule. Does 408.36 not allow me to run my service cable for 200 amps and install a main breaker in the panel for overcurrent protection? I realize that's not protecting the service cable but it does protect the panel board per the code in 408. I don't see a length limit in the 408 section. Or is this 2 completely seperate issues? Panel board and Feeder. I'm realizing that my SER from disconnect to panel is not technically a "service feeder" after first disconnect.
I reference the number of disconnect rule to lead to another question. What if I had 7 panels? Would I have to feed one from taps in another panel?
These are the finer points I find myself getting stuck on.

Yes, two completely different issues. The length of the feeder tap conductors is covered by the rules in 240.21(B).

 

[augie47]

The only possibility I see would be then 240.21(B)(5) tap rule which will require your 800 amp disconnect to be outside and your feeders to be outside and the 200 amp M/B panels to be outside or inside nearest to point of entry of the feeders,

 

[infinity]

The only possibility I see would be then 240.21(B)(5) tap rule which will require your 800 amp disconnect to be outside and your feeders to be outside and the 200 amp M/B panels to be outside or inside nearest to point of entry of the feeders,

I agree. Might not be feasible but by keeping the tap conductors outside there is no limit to their length.

 

[Jawrenn18]

Thanks for the info. Sounds like I've hit a speed bump. I read 408.36 where panel boards can be protected "up to or within" and figured I was covered. I wasn't thinking about it being service feeders and how the tap rule would override 408.
Now I'm just thinking out loud. Could I install inline fuses mounted to a block under the load side of the 800 amp disconnect provided manufacturer allows it and there is air space for them?

 

[hillbilly1]

Thanks for the info. Sounds like I've hit a speed bump. I read 408.36 where panel boards can be protected "up to or within" and figured I was covered. I wasn't thinking about it being service feeders and how the tap rule would override 408.
Now I'm just thinking out loud. Could I install inline fuses mounted to a block under the load side of the 800 amp disconnect provided manufacturer allows it and there is air space for them?

Why not just put four fusible or breaker disconnects next to the 800, taping there, then you can use MLO loadcenters wherever you need them off that? Put a tap can between those, and allow enough room to put in an 800 amp transferswitch when it comes in.

 

[Jawrenn18]

I have a "discerning" architect, designer and client who do not want "a bunch of boxes and pipe cluttering up the walls". So I was hoping to keep it in 1 enclosure. When Cummins said they couldn't get me the transfer switch/Main/switch gear until next year it was a real pain in the ass. Transfer switches are now going in line after the 800 amp disconnect but are non SE rated and have to be above flood which is +/- 8ft from slab. Again to keep from "cluttering up the wall" they are going up high on storage room wall in the ground floor. House was wired and set up for the combo unit on the service wall so I'm limited on that location for all this.

 

[jap]

One might consider setting the 800 amp fused disconnect beside a large hoffman enclosure with however many 200 amp 2p fuse blocks you need and size the tap conductors from the disconnect to the line side of the fuseblock to cover the tap rule.

The 800 amp disconnect will probably have enough individual lugs per phase to feed the number of 2p blocks you need at this time.

Leaving the neutrals from your SER's to reach the disconnect and all other field wiring extra long so when the combo Transfer Switch/Service Disconnect unit arrives you can swap everything over.

Just thinking out loud.

JAP>