3 phase panels

[Bigrhamr]

I've been following the 400 amp service thread with interest and picked up some good info there. I think I have my service figured out to where it enters the building. 400 amp meter then it looks like the exterior disconnects are going to be required. I'll have 2-200's.

Question number 1 is: Why are some disconnects fused and some not? Which do I want?

Question 2 is: So far the 3 ph panels I'm finding reasonably priced are either 200 amp with 30 spaces or 225 with 42 spaces which I would prefer. Any problem with 2-225's instead of 200's in this case?

And last question for the day is: With the 3ph panels can you put breakers in for the single ph loads or do you need to use sub panels for that? Pluses and minuses for either way? I'll likely have more single ph circuits than 3ph and I don't think that space will be an issue if I've got 42 spaces per panel.

Thanks for all the info here.

 

[tfi racing]

#1-Conductor size and length/distance will determine if you need fused or non fused disconnects,someone more familiar with your type of service will chime in soon

#2-Go with the 225A,42 cct-What brand are they?Have a look at the price/availability of breakers,you may not be able to get them at your consumer big box store.

#3-You can use one,two or three pole breakers to suit your load and feeder conductors as required.

Hope that helps.

 

[Charles (in GA)]

Are you talking three phase? or are you talking single phase, 120V/240V like you have in your house? Generally, three phase is not available to residential locations, unless you just happen to have three phase running down the road in front of your house, and three phase circuit breaker panels are quite pricey

Charles

 

[Bigrhamr]

Yes, I'm talking 3 phase 208/120v. I've been running off a rotary converter, now moving and building a new shop. One of the pluses for buying the place was having 3ph on the road right in front of the shop so I can get it hooked up pretty reasonable.

The panels I'm looking at are Square D QO 225 amp, 42 space/42 circuit main lug panels for about $185 each delivered if I buy 2 of them together.

 

[rinny_tin_tin]

I've been following the 400 amp service thread with interest and picked up some good info there. I think I have my service figured out to where it enters the building. 400 amp meter then it looks like the exterior disconnects are going to be required. I'll have 2-200's.

Question number 1 is: Why are some disconnects fused and some not? Which do I want?

Question 2 is: So far the 3 ph panels I'm finding reasonably priced are either 200 amp with 30 spaces or 225 with 42 spaces which I would prefer. Any problem with 2-225's instead of 200's in this case?

And last question for the day is: With the 3ph panels can you put breakers in for the single ph loads or do you need to use sub panels for that? Pluses and minuses for either way? I'll likely have more single ph circuits than 3ph and I don't think that space will be an issue if I've got 42 spaces per panel.

Thanks for all the info here.

Fused disconnects are typically used for motors with either high locked rotor current - or - in cases where the load is engaged at startup - like a positive displacement pump. If you have a motor needing a fused disconnect - you will know it.

 

[Aceman]

Bigrhamr,

I would check with your inspector to see if outside discos are required. Like I posted in the other thread, see if you can ****** through the wall into main breaker panels and ditch the disconnects. You could price it either way though, but personally, I'd go with the main breaker panels as long as your inspector has no objections for a couple reasons:

1. Looks cleaner on the outside, you're only going to see a meter with no extra disconnects.
2. No disconnects to buy, less material, shorter wire lengths since you'd be chasing wire right into the panel from the meter rather than looping it from the meter to disco to panel.

 

[Bigrhamr]

It sounds like they are going to want the outside disconnects with a possible exception if the panels are right inside the main entrance door. I don't want them there so I don't think that will fly. Now I found the local Home Depot has Seimens 3ph 225A main lug 42/42 panels for $124 which seems like a pretty good deal. 3 pole breakers for it are about 3 times the price of 1&2 pole but I think that's pretty typical from what I've seen.

Does 2/0 copper sound right for the short run feeding the 225's? Does code let you downsize the neutral? What size ground?

Also is there a NEMA code or number signifying what is an exterior enclosure?

Thanks!

 

[walrus]

Also is there a NEMA code or number signifying what is an exterior enclosure?

Thanks!

Nema 3 or 3R I believe

 

[Aceman]

Does 2/0 copper sound right for the short run feeding the 225's? Does code let you downsize the neutral? What size ground?

This is a 400 amp service, right? So your feeding each 225 amp main lug panel with a 200 amp disconnect, correct?

3/0 Thhn Cu for 200 amps

Neutral can be reduced if you have a load calc showing the neutral has less load on it, otherwise it's full sized. Typically, we drop it down to a 1/0 if we know there will be a lot of line-line rather than line-neutral loads.

#6 Thhn Cu for a ground.

Also is there a NEMA code or number signifying what is an exterior enclosure?

What Walrus said, 3R.