Commercial line side tap of sorts

bottlefed67

I have an existing 2000A 120/208 3-phase multi meter main. The meter that I need to feed into has an existing 200A fusible pullout feeding a 200A subpanel. What I'm proposing is setting a new 200A "panel" of some sort inline on the sub-feed that will house (5)-40A back feed breakers and (1)-200A breaker feeding out to the existing sub-panel. The bussing would never see more than a 200A load because of the 200A breaker feeding the existing sub-panel. I've talked to the local building official and he said this would be okay as long as the new panel isn't a "sub-panel". Any ideas on how this could be accomplished or any other ways of doing this that you guys can come up with? Does the code allow my layout?

Thanks in advance for any advise.

BB.

Re: Commercial line side tap of sorts

Note, there is a an area between the fuse output and the input of the two boxes where 400 amps is available (sum of utility main and GT Inverter to the intermediate power bus.

You may have to research how much current it is rated to carry to satisfy your inspectors.

-Bill

bottlefed67

Re: Commercial line side tap of sorts

So you're saying I might have to use a new 400A panel instead of a 200A.

BB.

Re: Commercial line side tap of sorts

I am not an electrician or a code guy... I do not know what will be required.

But, it is possible. As a systems designer--Looking for places like this where you have more current than the original design did not (i.e., box without GTI), was something that I had to look for in N+1 redundant computer systems designs.

-Bill

solar_dave

Re: Commercial line side tap of sorts

bottlefed67 wrote: »

So you're saying I might have to use a new 400A panel instead of a 200A.

I am sure it depends on the sizing of the upstream components. If the service feed and such are rated for 400 amps seems that they might allow a 200 amp panel add.

Disclaimer I am just a guy, not an EE, Code dude, or Electrician.

That being said, I was required to upgrade everything back to the transformer to 400 amp service feed to do dual 200 amp panels.

jaggedben

Re: Commercial line side tap of sorts

bottlefed67 wrote: »

So you're saying I might have to use a new 400A panel instead of a 200A.

You definitely need to use a 400A panel, according to the code. 690.64(B) in 2008 or earlier, 705.12(D) in 2011. The 120% rule.

Technically you could use anything down to a 334A panel, if you could find that, but I think you'd end up with 400A.

One thing you didn't completely make clear is whether all the breakers mentioned are 3-pole or not. It might change the math a bit if the backfed breakers are not 3-pole and your inverters are not 3-phase (although that might beg further questions about how you are balancing phases with 5 inverters).

jaggedben

Re: Commercial line side tap of sorts

solar_dave wrote: »

I am sure it depends on the sizing of the upstream components.

Not really. The bus rating of the panel he is proposing to install is determined by the ratings of the OCPDs supplying it.

If he is proposing to use some existing busing between the existing 200A pullout and his new panel, then the rating of that busing needs to be above 334A.