300 Amp Service

 
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Old 03-12-2008, 08:12 PM   #1
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300 Amp Service


I have a 300 amp, 120/ 240 Volt single-phase service to install. I plan on mounting (2) 200 amp main breaker panels. I don't want to come out of the 320 amp meter base twice with 2 pieces of conduit (1 to each panel), so can I run one conduit with three 250 kcmil conductors to a trough and tap it with 2 sets of 2/0 conductors to each panel? The trough will mounted above each MB panel.
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Old 03-12-2008, 08:33 PM   #2
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Re: 300 Amp Service


Fine except you need 350mcm copper, not 250's. This is unless you really are calling this a "300 amp" Service. Typically what you are doing is a 320A service.
Your POCO will confirm.

Can I ask why you want to go through so much extra work and expense?

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Old 03-12-2008, 08:51 PM   #3
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Re: 300 Amp Service


also, check the meter....many of them come set up for parallel conductors, so you can just run a 2/0 (assuming this is a house) through the trough and into each panel...no need to bug in the trough and much easier to work with...
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Old 03-12-2008, 09:03 PM   #4
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Re: 300 Amp Service


The official plans call for a 300 amp service. House is 3900 sq ft. Somebody else did all the load calcs and I'm just wiring for what the plan calls for. Only "big loads" on the plan are 3 ton, 4 ton, and 5 ton A/C condensors. As usual, the kitchen plan is still in the works.

I did a 400 amp service like this last year (same set up), except the underground SEC's were 350's. I don't have the meter base just yet but I am assuming JCPL has the double-barrel lugs. If this is the case, am I running 6-2/0's through say a 3" PVC pipe to the trough?
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Old 03-12-2008, 09:07 PM   #5
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Re: 300 Amp Service


Quote:
Originally Posted by Magnettica View Post
... The trough will mounted above each MB panel.
I do that, sometimes. You're aparently working from plans, but when I use that method, it's because I want to set three panels. Two, 200A panels, and one to a 100A disco feeding a 100A ATS feeding a 100A panel for the "emergency loads" that are on generator. If I'm just setting two panels, I just run two pipes to save the extra expense and hassle of the gutter. I have already run to a gutter to set 4 or 5 panels on a 320 service just for more "spaces" in a plan that has way too many home runs called out.
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Old 03-12-2008, 09:14 PM   #6
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Re: 300 Amp Service


Two conduit runs from the meter is gonna look crappy. The meter gets mounted on a different outside wall from where the conduit will enter the house because there's window in the way. I could put both panels in the garage but that creates an even bigger pita wiring the place up. The panels in the basement makes my life easier for the next month. Did I mention I'm wiring the whole house myself? 100-something hi-hats, 5 bathrooms, 10' high ceilings, 90% chance of a finished basement too.
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Old 03-12-2008, 09:15 PM   #7
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Re: 300 Amp Service


I'll snap off some pictures tomorrow.
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Old 03-12-2008, 09:17 PM   #8
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Re: 300 Amp Service


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Did I mention I'm wiring the whole house myself?
Do you mind that, very much? I happen to prefer to work alone, even on bigger work like that. I've maintained my whole career that there are no 2-man jobs in the electrical trade. Some things do go easier with 2 men, like fishing in an old building, but it can be done with one. I like to wire new work by myself. No wasted time communicating the day's plan to another person or persons. Just have at it. The drawback is that you don't have the extra set of eyes on your work that is sometimes appreciated, and you need to make sure you didn't miss anything (like a home run ).
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Old 03-12-2008, 09:20 PM   #9
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Re: 300 Amp Service


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Two conduit runs from the meter is gonna look crappy.
Sounds like a perfectly reasonable reason to use a gutter, to me. I might suggest that since you're going to be using a gutter, leave it long enough to set an extra panel or ATS down the road if it ever comes to that and if it will fit. The next guy might appreciate it, and that next guy might be you! The extra material cost would probably be around 15 bucks, so it's not really something that normally needs discussed, unless you see some reason why a gutter an extra foot or two long would be objectionable.
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Old 03-12-2008, 09:22 PM   #10
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Re: 300 Amp Service


I do like working alone because I know it'll get done the way I want it to. The only part I dont like is cleaning up, locking up the generator, ladders, and materials by myself. It would also be nice to have someone to go out and get coffee/ lunch. I'll request some help from the shop when the hi-hats are ready to be tied-in but somehow the youngin's will still manage to screw that up.
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Old 03-12-2008, 09:23 PM   #11
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Re: 300 Amp Service


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Originally Posted by Magnettica View Post
I'll request some help from the shop when the hi-hats are ready to be tied-in but somehow the youngin's will still manage to screw that up.
I notice that many brands are coming with the Wago style connectors in them now from the factory, so that's sorta neat. I'm still a little suspicious on exactly how many fixtures I'd want to "feed through" a Wago near the beginning of a large run of cans.
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Old 03-12-2008, 09:27 PM   #12
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Re: 300 Amp Service


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Originally Posted by mdshunk View Post
I notice that many brands are coming with the Wago style connectors in them now from the factory, so that's sorta neat. I'm still a little suspicious on exactly how many fixtures I'd want to "feed through" a Wago near the beginning of a large run of cans.
I'm using Halo H7T & H7ICT. In fact, I measured for and installed 85 of them yesterday. I'm a big fan of the Wago connectors AND the new plastic 'slot' connectors that come stock with the Halo cans. both of those features make life alot easier.
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Old 03-12-2008, 09:33 PM   #13
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Re: 300 Amp Service


If you have the space in the first panel, you could use a large(3") nipple from the meter to the first panel, and a 2" nipple between panels and chase the second set of conductors through the first panel to the next. I don't have my Code book with me today, left it on the job, but I think it is addressed in 312.8 (or maybe 312.6, not sure). Should be legal and neat.

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Old 03-12-2008, 09:52 PM   #14
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Re: 300 Amp Service


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Should be legal and neat.
Sure would be, but I think he's saying that they're not back to back, and the meter is located some distance from the panels. I suspect, also, that these panels are going in the basement.
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Old 03-12-2008, 11:36 PM   #15
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Re: 300 Amp Service


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I've maintained my whole career that there are no 2-man jobs in the electrical trade.

Pulling wire can be a chore, especially feeders


I have gotten too old, spoiled and lazy. It is nice to have someone just to run to the truck and clean up.
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Old 03-13-2008, 12:10 AM   #16
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Re: 300 Amp Service


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Sure would be, but I think he's saying that they're not back to back, and the meter is located some distance from the panels. I suspect, also, that these panels are going in the basement.
Oops! Missed that part entirely. Sorry

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Old 03-13-2008, 09:37 PM   #17
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Re: 300 Amp Service


Ok, here's a picture. The exterior wall on the left hand side is where the meter will go. The feeders will 90 out of the bottom of the meter, 90 around the corner, and LB into the rim joist beneath the window. The exterior of the house will be finished in brick.



Since I'm planning on using 2/0 -- and use 6 of them in one 3" ridgid nonmetallic conduit -- do the feeders need to be derated? I'm using 2/0 based on Table 310.15(B)(6).

Also, how would YOU go about grounding and bonding the 2 panels?

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Old 03-14-2008, 06:07 AM   #18
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Re: 300 Amp Service


yes, you need to derate them....
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Old 03-14-2008, 12:03 PM   #19
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Re: 300 Amp Service


It's a shame to build a nice house with an overhead service. In Albuquerque we haven't done a new overhead service in 20 years.
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Old 03-15-2008, 06:47 PM   #20
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Re: 300 Amp Service


Are you using a meter/main or just a meter socket with the mains in the panels? If it is a meter/main with two mains, then you would bond your neutral once at the meter and run a separate EGC to your panels.

If it is a meter socket, and the mains are in the panels, you can either bond at the meter socket and the bond your panels to the neutral, or you can bond at the weather head and bond your panels to the neutral.

You can run two GECs to each panel and bond them together at the point of termination at your rods or cold water (or whatever), but I don't like this idea myself, because it gives neutral current from each panel a path to flow to the neutral in the other panel.

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