400 amp service

Status
Not open for further replies.
K

Kessler4130

Senior Member
Location
Maryland
A job I am looking at has a 400 amp service and wants it somewhat setup for a future generator (85kw), can I use a 400 amp disconnect and supply 2, 200 amp main lug panels from this with parralel 3/0 copper ? It is probably a stupid question but I just wanna make sure.
 
I think those two panelboards need to have 200-amp main circuit breakers if you do as you suggest. Do away with the 400-amp disconnect and tap the service conductors to feed two 200-amp main breaker panels. Each of those breakers will become your service diconnects and the panels must be located next to each other. Each panel must be service entrance rated.
 
I like hbendiilo's suggestion. Unless for some reason you cannot group the two panels together or have them located nearest the point of entry of the service entrance conductors.
 
infinity said:
I like hbendiilo's suggestion. Unless for some reason you cannot group the two panels together or have them located nearest the point of entry of the service entrance conductors.
Click to expand...
The panel boards are located next to eachother but due to the position of the service pole I cannot say that the metering equipment will be near the panel so I figured on a disconnect at the metering equipment anyways. With the 400 amp disconnect can I still feed 2, 200 amp panels if I use 200 amp main breaker panels ? And again they want to make it future generator friendly so I was figuring on bringing both loads from the disconnects into a trough under the panels so when they eventually set the ATS they wont have to rip everything apart.
Any input would appreciated :).
 
Does your customer have any idea how much a 400 amp ATS and a 85kw generator cost? You might be able to talk a little reason into them, and do two, 200 amp MB panels, and set up a sub off one of them as an 'emergency panel', and put in a more reasonably sized ATS and genset. Your proposal in the opening post is super-mega bucks.
 
If you use a 400 amp disconnect with a 400 OCPD and then feed the two 200 amp panels with 200 amp conductors those conductors become taps and are limited to 25' in length. The panels would still require a 200 amp mains.
 
mdshunk said:
Does your customer have any idea how much a 400 amp ATS and a 85kw generator cost? You might be able to talk a little reason into them, and do two, 200 amp MB panels, and set up a sub off one of them as an 'emergency panel', and put in a more reasonably sized ATS and genset. Your proposal in the opening post is super-mega bucks.
Click to expand...
I'd suggest setting up one of the 200a panels as the generator panel, and using a 200a T/S.
 
I would like to suggest an energy management system. I did a house or I should say an estate that had a 1200 amp service with 13 hvac systems. The entire project was done with one 100kw generator by using the energy management system. This sytem prioritizes the loads , esp the a/c so that no more than one or two units are on at the same time.

It works wonderfully. Since the heavy loads cannot come on at the same time the need for a larger generator was not necessary. The plus is that the power company also gives a rebate monthly on the energy management system.
 
Is it just my perception, or does your customer think all this is going to happen for free or pretty darn close to it?

I was chewing the fat with my brother's neighbor about what it would take to set his house up for a typical generac. This was at a BBQ after the NE blackout. I asked why he thought he'd need such a large permanent unit for a once in a blue moon event. Because he saw it in the lobby of home depot, panel and everything included. When I asked what he'd like to run in the event of a blackout, I think he included every circuit he had because at least one thing on each circuit was deemed "can't live without."

I think I could live with a 9kv unit.
 
Kessler4130 said:
The panel boards are located next to eachother but due to the position of the service pole I cannot say that the metering equipment will be near the panel so I figured on a disconnect at the metering equipment anyways. With the 400 amp disconnect can I still feed 2, 200 amp panels if I use 200 amp main breaker panels ? And again they want to make it future generator friendly so I was figuring on bringing both loads from the disconnects into a trough under the panels so when they eventually set the ATS they wont have to rip everything apart.
Any input would appreciated :).
Click to expand...


Yeah, if they want to connect the entire building to a generator it would make sense to go ahead and set that 400-amp disconnect. Can you leave room next to the 400-amp disconnect for a transfer switch? That way in the future they can just break the service through the transfer switch and leave the rest alone. They could use a manual transfer switch if the load is not critical. I have done a couple of projects where the emergency side of the transfer switch is fed through a big pin and sleeve receptacle so one could park a portable generator next the buidling whenever needed. Permanent generators require permanent connections though.
 
infinity said:
If you use a 400 amp disconnect with a 400 OCPD and then feed the two 200 amp panels with 200 amp conductors those conductors become taps and are limited to 25' in length. The panels would still require a 200 amp mains.
Click to expand...
Not if those tap conductors are located outside and the rules of 240.21(B)(5) are followed. :grin: You can run any length desired.
 
kbsparky said:
Not if those tap conductors are located outside and the rules of 240.21(B)(5) are followed. :grin: You can run any length desired.
Click to expand...


The disconnect is outside, and the panels are ofcourse inside, the generator is not in my scope of work, they simply cannot afford it but want to be set for a future install. They also intend to run the entire building off the genset. I say 85kw simply because thats what the drawings propose I have not done a load calculation yet, so that could change.

And let me clarify a few things, this is a Veterinary Center, it is not a residence. If it weren't for the intent of a future ATS I would simply use 2, 200 amp disconnects outside, and there is room in the mechanical room for an ATS next to the panel.

Once again any feedback is appreciated, you guys are lifesavers.
 
Last edited:
kbsparky said:
Not if those tap conductors are located outside and the rules of 240.21(B)(5) are followed. :grin: You can run any length desired.
Click to expand...

You're correct. I was assuming that the panels where located somewhere remotely on the inside.
 
Kessler4130 said:
A job I am looking at has a 400 amp service and wants it somewhat setup for a future generator (85kw), can I use a 400 amp disconnect and supply 2, 200 amp main lug panels from this with parralel 3/0 copper ? It is probably a stupid question but I just wanna make sure.
Click to expand...

Parallel 3/0 should be good for 360 amps which would mean your calculated noncontinues load would have to be less than 288 amps. Looking at 215.2.
 
Cody K said:
Parallel 3/0 should be good for 360 amps which would mean your calculated noncontinues load would have to be less than 288 amps. Looking at 215.2.
Click to expand...


How did you come up with 360 amps? #3/0 is rated for 200 amps a 75 degrees C. 200*2 = 400 amps
 
Well, I used 90 degrees C. That would be 3/0 good for 225 A. Then I derated wire by multiplying 80%. 180 A x's 2 = 360 A.

Please correct me where I am wrong and advice reference. Thanks
 
Cody K said:
Well, I used 90 degrees C. That would be 3/0 good for 225 A. Then I derated wire by multiplying 80%. 180 A x's 2 = 360 A.

Please correct me where I am wrong and advice reference. Thanks
Click to expand...

Are you using the 90 degree C column and then derating the cables for more than 3 current carring cunductors in raceway per Table 310.15(B)(2)(a)?

If that is the case why not just run two conduits then the cable from the 75 degree C colum will be good for 400 amps.
 
That is an option. My thought from OP is that it was not being seperated into two raceways going from service disconnect into subpanels.
 
Cody K said:
That is an option. My thought from OP is that it was not being seperated into two raceways going from service disconnect into subpanels.
Click to expand...

I would be using 2 raceways, and am pretty much leaning towards a 400 amp panel board and a 200 amp sub. I certainly dont want to do it twice. Under what conditions can a feed through panel be used ? square d's website isn't being much help because they have little to no info on anything over 200 amps. I am looking for a cost effective solution and a 400 amp panel with sub is not quite in that area.

The service will be on the west wall and the actuall panels on the south wall, so the conductors will remain outside, until they enter ofcourse.
 
It would be nice if you could purchase the ATS now. Mount downstream of meter. Then install a trough in which you could split off and mount two 200 disconnects to act as feeder for your panelboards.

This would allow simply coming in whenever the genset is purchased and wiring into the ATS and setting up controls.
 
Status
Not open for further replies.
Top