Main Panel Disconnect

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kriverswaters

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I am estimating on installing a 320 Amp overhead residential service with two 200 Amp 42 circuit panels. One 200 Amp panel will be located right behind the new meter base in the basement of this residence. The other 200 Amp panel will be located approximately 70' on the next floor up. Do I have to have a disconnect between the meter base and the second panel because of the distance? Will 300MCM in a 2 1\2" Rigid metal Conduit be be?adequate enough for this service? KRiverswaters@aol.com
 
roger

roger

Moderator
Staff member
Location
Fl
Occupation
Retired Electrician
Re: Main Panel Disconnect

See articles 230.72 and 310.15(B)(6)

Roger
 
iwire

iwire

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Staff member
Location
Massachusetts
Re: Main Panel Disconnect

Originally posted by kriverswaters:
One 200 Amp panel will be located right behind the new meter base in the basement of this residence. The other 200 Amp panel will be located approximately 70' on the next floor up. Do I have to have a disconnect between the meter base and the second panel because of the distance?
Click to expand...
Yes you will need overcurrent protection and you will need the disconnects 'grouped'

I would look for a 320 meter socket with provisions for two 200 amp breakers.
 
R

rasmithircgov.com

Member
Location
Florida
Re: Main Panel Disconnect

Yes,
Art 225.34 (A) General. The two to six disconnects as permitted in 225.33 shall be grouped. Each disconnect shall be marked to indicate the load served. Also ART. 230.70(A)(1) Readily Accessible Location. The service disconnecting means shall be installed at a readily accessible location either outside of a building or structure or inside nearest the point of entrance of the service conductors. So it would have to be a sub panel upstairs.
Hope this helps. ;)
 
roger

roger

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Location
Fl
Occupation
Retired Electrician
Re: Main Panel Disconnect

rasmithircgov.com, article 225 doesn't apply here.


Article 225.34 is addressing "feeders" for More Than One Building or Other Structure

Go two sections past 230.70. :roll:

Roger
 
iwire

iwire

Moderator
Staff member
Location
Massachusetts
Re: Main Panel Disconnect

Originally posted by kriverswaters:
Will 300MCM in a 2 1\2" Rigid metal Conduit be be?adequate enough for this service?
Click to expand...
No

The service conductors will need to be 400 kcmil copper or 600 kcmil aluminum minimum.

Unless you plan on using Exception No. 3 to 230.90(A) ;)
 
B

benaround

Senior Member
Location
Arizona
Re: Main Panel Disconnect

A SIMILAR SITUATION CAME THRU HERE A FEW DAYS BACK AND BOTH FEEDERS WERE REQUIRED TO HAVE OCPD AT THE METER LOCATION--GROUPED!!
 
J

jeffrose

Member
Re: Main Panel Disconnect

Millbank makes a 320 meter with two 200A disconnects. Your pretty brave purchasing 500kcmil wire with prices the way they are. I'd parallel the conductors in a larger pipe. :cool:
 
iwire

iwire

Moderator
Staff member
Location
Massachusetts
Re: Main Panel Disconnect

Jeff I do not see prices, I order stock and it arrives so I am curious about what you said.

If you go parallels in one pipe you will be using 310.16 and need 2 sets of 250 kcmil cu for the 400 amp service.

If you use one set of conductors you can use Table 310.15(B)(6) resulting in one set of 400 kcmil cu, it is available.

Would 250 kcmil really be 50% or less per ft than 400 kcmil? :confused:
 
D

drg

Senior Member
Re: Main Panel Disconnect

Bob, im following along how you use table 310.15(b)(6) when using a 3 wire feed... 400 mcm for a 400amp service .

Then when(if)you parallel you go to table 310.15(b)(2)(a) .....using the 80 % factor for 4 current carring conductors I come up with 4/0 for the wire to be used.

I am taking 260 x 2 divded by 80% = 416 amps

You say 250 mcm is the wire to be used, I just must be missing something or going about this wrong somewhere ...can you help clear this up for me and explain what I am overlooking ????

Thanks John :)

[ March 23, 2004, 10:59 PM: Message edited by: drg ]
 
tshea

tshea

Senior Member
Location
Wisconsin
Re: Main Panel Disconnect

Table 310.15(B)(6)
single riser and weatherhead
350 cu for 350Amp service
---------------
2 risers and 2 weatherheads
1/0 cu X 2= 175 X 2= 350 Amp service
---------------

parallel conductors using Table 310.16
310.15(B)(6) already derates conductors, so you need to use ful rating from 310.16

6-#3/0 cu
225A (90 col) X .8= 180A X 2= 360 Amp service
----
6-#2/0
195A (90 col) X .8= 156 X 2= 312 Amp service
 
iwire

iwire

Moderator
Staff member
Location
Massachusetts
Re: Main Panel Disconnect

John my numbers are based on a 400 amp service.

A 320 meter socket is rated 320 continuous, 400 max.

I do not believe you can use table 310.15(b)(2)(a) for parallel conductors.

Table 310.15(b)(2)(a) is not the rating of conductors it just modifies how conductors can be used in certain situations.

However after looking at this again 4/0s do seem to fit the bill. :)

For derating purposes 310.16 rates 4/0 copper as 260 amps.

260 x 2 x .8 = 416 amps.

You might even be able to use 3/0s

225 x 2 x .8 = 360

Using 240.4(B) this could be protected at 400 amps if the calculated load was less than 360 amps.

I would be more comfortable with 4/0 then you do not have to worry about future loads exceeding 360 amps.

This would change if this was an underground service, then you would have to consider it a wet location and you would have to derate from the 75 C column instead of the 90 C column as I did above.

But the inspector might want to call the conductors in the raceway down the side of the house as wet location. :D

A lot of thought to this when in the end Charlie's guys will come along with 1 AWG or 1/0 aluminum to feed these conductors. :D (And it will work fine :cool: )
 
P

pierre

Senior Member
Location
Westchester County, New York
Re: Main Panel Disconnect

It is interesting to see the different methods and results for sizing conductors. :D
How about the service disconnect locations?
The key here is the proper or improper language that is used.
Service Drop
Service Entrance Conductors
Service Point
Service Lateral
Service-Entrance Conductors, Underground System
Service
Service Equipment -see last sentence in 230.66
Feeder Conductors
ETC...

Where does a service start and where does it end?

I think that if you understand these terms, it is a lot easier to read the NEC.

Pierre

[ March 24, 2004, 07:31 AM: Message edited by: pierre ]
 
R

rasmithircgov.com

Member
Location
Florida
Re: Main Panel Disconnect

What about this art?
310.4 Conductors in Parallel.
Aluminum, copper-clad aluminum, or copper conductors of size 1/0 AWG and larger, comprising each phase, neutral, or grounded circuit conductor, shall be permitted to be connected in parallel (electrically joined at both ends to form a single conductor). Is this parallel conductor one conductor and by definition would 310.15(B)(6) apply? :confused:
 
D

drg

Senior Member
Re: Main Panel Disconnect

rasmith, if the question was, are groups of paralleled conductors considered "one conductor" that makes up a phase , I would say yes.

Would article 310.15 (b)(6)apply to these conductors?
I would say yes if it was for a single phase dwelling service or feeders.

John
 
D

drg

Senior Member
Re: Main Panel Disconnect

rasmith, I might have been to quick to answer that question the way I did, and answered without really checking the book.

Now I have doubts and see part of what your getting at, there seems to be a twist here that I might be missing ,good question though.

Have about 15 minutes before leaving house for the day .will check back later today.

John
 
B

bonding jumper

Senior Member
Re: Main Panel Disconnect

For the NYC area, the PO CO, Con Ed only allows meters to be rated a max of 200 amps. Larger services require a current transformer (CT) cabinet to a 10 point meter. He would not be reqired to do so in this case?
 
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