new 400 amp resid. service

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meptech

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I have a design question. With so many new large houses, most require 400 A service. How does a 400A single phase, 120/240 service for the residential application look like when the service outside is some distance away from the inside disconnects and one would need an outside disconnect.
The main service is underground, meter is outside against the house, and the two 200 amp panels are inside the house about 30? away. I can't find a meter set with a 400A MCB or one meter with 2-200A MCB's on it. Should I consider a 400A, 1PH, FSS?
 
There are combo units that are rated 400 amps and have 2-200 amp breakers to feed the interior panels. The other way is to install a 400 amp meter base with 2- 200 amp panels with feed thru lugs-- one on each side of the base.

When you are checking for a 400 amp unit be creful because they are label differently than the 200 amp bases. A 200 amp base is rated 200 amp noncontinuous load but only 160 continuous. The same is for a 400 amp unit. They are usually label with their continuous rating at 320 but are good for 400 noncontinuous.

Basically you are looking for a 320 amp combo unit not a 400 amp unit.
 
meptech said:
I can't find a meter set with a 400A MCB or one meter with 2-200A MCB's on it.
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I'd say you just havn't looked hard enough. I wouldn't call that hard to find equipment. The 400 amp meter can with (2)200 amp breakers is pretty common. It's big, though, so be warned.
 
Why not comply with 230.6 Conductors Considered Outside the Building? (4) Where installed in conduit and under not less than 450 mm (18 in.) of earth beneath a building or other structure.

If this job was done in this manner, you would not be required to have a disconnecting means on the outside of the home. Keep in mind that since neither of the 200 ampere services serve as the main power feeder, Table 310.15(B)(6) is not permitted to be used and you will be required to use Table 310.16. :)
 
charlie said:
Why not comply with 230.6 Conductors Considered Outside the Building? (4) Where installed in conduit and under not less than 450 mm (18 in.) of earth beneath a building or other structure.
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I was going to suggest that, but I figured the job was too far along.
 
charlie said:
Why not comply with 230.6 Conductors Considered Outside the Building?
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If I read him right, he says that the panels are 30 feet inside the house (somewhere in the middle). If the place has a basement, and the panels are upstairs, this wouldn't work. Even if the place was on a slab, it still might not work in my area, anyhow. They'd start their "measurement" of the max amount of unfused service conductors at 18" below grade, then up to the panel's lugs. I get 3 feet in my area, so I'd be over that limit unless I mounted my panels a foot off the deck. :)
 
charlie said:
Why not comply with 230.6 Conductors Considered Outside the Building? (4) Where installed in conduit and under not less than 450 mm (18 in.) of earth beneath a building or other structure.

If this job was done in this manner, you would not be required to have a disconnecting means on the outside of the home. Keep in mind that since neither of the 200 ampere services serve as the main power feeder, Table 310.15(B)(6) is not permitted to be used and you will be required to use Table 310.16. :)
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Another gift of the 2008 code....as I read it:)

steve
 
We usually set the 320a meter base and run 2 4/0 sec into 2 weatherproof 200 amp main breaker enclosures and then 4/0 ser to the 2 200amp mlo in the house.
You may have to go to the bank to get a loan to buy the 4/0 ser
 
fisherelectric said:
We usually set the 320a meter base and run 2 4/0 sec into 2 weatherproof 200 amp main breaker enclosures and then 4/0 ser to the 2 200amp mlo in the house. . .
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If you are using Al conductors, 4/0 is not large enough. If you are using Cu conductors, 4/0 is one size larger than you need.

Keep in mind that since neither of the 200 ampere feeders serve as the main power feeder, Table 310.15(B)(6) is not permitted to be used and you will be required to use Table 310.16. :smile:
 
meptech, i use a 400A meter base and put a squareD qom2 enclosure on each side w/ 200A cb installed. the qo2 is about 10" wide, maybe 24" high; it keeps the size down. occasionally i install a 200A panel w/ feed-thru lugs if requested. squareD makes a 400A meter base w/ 2x200A cb's, but its about the size of a truck hood and weighs at least 100/lbs.
 
charlie said:
If you are using Al conductors, 4/0 is not large enough. If you are using Cu conductors, 4/0 is one size larger than you need.

Keep in mind that since neither of the 200 ampere feeders serve as the main power feeder, Table 310.15(B)(6) is not permitted to be used and you will be required to use Table 310.16. :smile:
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So why wouldn't 240.4(B) come into play as long as the calculated load for either panel wasn't over 180 amps
 
"Keep in mind that since neither of the 200 ampere feeders serve as the main power feeder, Table 310.15(B)(6) is not permitted to be used and you will be required to use Table 310.16"


The code says " the main power feeder(s) shall be the feeders between the main disconnect and the lighting and appliance panelboards." That is what these feeders (the 4/0 SER) are.
 
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fisherelectric said:
"Keep in mind that since neither of the 200 ampere feeders serve as the main power feeder, Table 310.15(B)(6) is not permitted to be used and you will be required to use Table 310.16"


The code says " the main power feeder(s) shall be the feeders between the main disconnect and the lighting and appliance panelboards." That is what these feeders (the 4/0 SER) are.
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I believe that is what Charlie stated in post #13, however T310.15 has 4/0 aluminum rated at 180 amps-- 240.4 allows us to go one size higher as long as the load is not greater than 180.
 
Dennis,

Table 310.15(B)(6) rates 4/0 Al for 200 amp service or feeder conductors for residential services.
I think Charley was saying that in this situation the 4/0 SER is not a feeder as per T310.15(B)(6), which I believe it is. If it isn't I sure have installed a lot of under-sized feeders.
 
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fisherelectric said:
Dennis,

Table 310.15(B)(6) rates 4/0 Al for 200 amp service or feeder conductors for residential services.
I think Charley was saying that in this situation the 4/0 SER is not a feeder as per T310.15(B)(6), which I believe it is. If it isn't I sure have installed a lot of under-sized feeders.
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Charlie is correct. The 4/0 SER is not a feeder as defined in 310.15(B)(6) because it does not carry the full load of the service. This was clarifired in the NEC 2008. In the 2005 it was definitely questioned.
 
I'm working under the '05 here, but still don't understand why it doesn't qualify as a main power feeder as these are straight runs from the main breakers to the MLO panels. Is it because there are 2 feeders? In the '05 the book says " feeder(s)between the main disconnect and the lighting and appliance panelboard(s)".
 
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