# 400 amp service county requiring 600alu for mast?



## Lythropus (Jan 27, 2009)

I just finished a 400 amp residential service that consisted of a 400 amp meter base that feeds two 200 amp exterior service disconnects and two 200amp interior panels. I ran a 3 1/2" pvc mast about 8 feet or so with paralleled 4/0 alu up the mast. On 310.16 excemption 4 says I don't have to derate the conductors in conduit less than 10 ft. but the county inspector failed me and is requesting 600alu or paralleled 300's up the mast? It also rates 4/0 alu at 200 amp for a service feeder application. He says it's in the IRC book but I don't have that in front of me at the moment. What's the deal? I'm of course going to change it tomorrow 
morning(Just to get the inspection passed) but this just doesn't seem right to me.


Thanks for the help in advance
-James


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## NolaTigaBait (Oct 19, 2008)

4/0 is too small. Can't use 310.16b6 for the subpanels.


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## Selectric (Aug 18, 2009)

310.15(B)(2)(a) _Exception No. 4: Derating factors shall not apply to underground conductors entering or leaving an outdoor trench if those conductors have physical protection in the form of RGS, IMC or ridig nonmetallic conduit having a length not exceeding 3.05 m (10 ft) and if the number of conductors does not exceed four._

Your installation is a mast that has parallel 4/0. You can not use this exception. You must derate.

Why didn't you just run parallel 4/0 SEU?

NolaTigaBait 310.15(B)(6) does allow you to use the conductors sized for the service-entrance as the feeder from the main disconnect to the panelboard.


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## NolaTigaBait (Oct 19, 2008)

> NolaTigaBait 310.15(B)(6) does allow you to use the conductors sized for the service-entrance as the feeder from the main disconnect to the panelboard.


Only can use that chart if it the main feed coming in. From the drop to the line side of meter use 310.16b6 and the load to the panels use 310.15


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## Lythropus (Jan 27, 2009)

So your basically saying that even though I have 2 4/0 seu up the mast (bare removed) and a 4/0 seu cable feeding each panel I still must derate to 80% of original load capacity because I'm running between 4 to 6 load carrying conductors in a pipe?

-james

Addition: Isn't 600alu XHHW still only 385?


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## NolaTigaBait (Oct 19, 2008)

Lythropus said:


> So your basically saying that even though I have 2 4/0 seu up the mast (bare removed) and a 4/0 seu cable feeding each panel I still must derate to 80% of original load capacity because I'm running between 4 to 6 load carrying conductors in a pipe?
> 
> -james


Yeah, I re-red the exception and it says for underground installations as well. The feeders to the panels can't be 4/0 alum. It's pretty stupid, but it is what it is.


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## Lythropus (Jan 27, 2009)

so what does everyone else use for the mast and feeders to the panels on a 400 amp?


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## Lythropus (Jan 27, 2009)

Ok I seriously didn't think I had to derate my service, I thought 310.15(b)(6) was gold like it was. And I was wrong about the exemption...hmmm


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## McClary’s Electrical (Feb 21, 2009)

310.15 (b) 2 (a) says conductors leaving the ground, yours are not, they're leaving the meter base.


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## heel600 (Oct 31, 2007)

Lythropus said:


> I just finished a 400 amp residential service that consisted of a 400 amp meter base that feeds two 200 amp exterior service disconnects and two 200amp interior panels. I ran a 3 1/2" pvc mast about 8 feet or so with paralleled 4/0 alu up the mast. On 310.16 excemption 4 says I don't have to derate the conductors in conduit less than 10 ft. but the county inspector failed me and is requesting 600alu or paralleled 300's up the mast? It also rates 4/0 alu at 200 amp for a service feeder application. He says it's in the IRC book but I don't have that in front of me at the moment. What's the deal? I'm of course going to change it tomorrow
> morning(Just to get the inspection passed) but this just doesn't seem right to me.
> 
> 
> ...


 


Shows you what I know.

I thought you size service conductors based on the calculated load.


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## Selectric (Aug 18, 2009)

NolaTigaBait said:


> Only can use that chart if it the main feed coming in. From the drop to the line side of meter use 310.16b6 and the load to the panels use 310.15


The more I read 310.15(B)(6) the more I see that is says you can use the conductor sized for the service-entrance all the way through to the panel board. This is a residential job not a commercial job. In residential you are allowed 4/0Al for a 200a service. 

I have always installed residential services that way and never had any issues.

Correct me if I am wrong.


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## NolaTigaBait (Oct 19, 2008)

Selectric said:


> The more I read 310.15(B)(6) the more I see that is says you can use the conductor sized for the service-entrance all the way through to the panel board. This is a residential job not a commercial job. In residential you are allowed 4/0Al for a 200a service.
> 
> I have always installed residential services that way and never had any issues.
> 
> Correct me if I am wrong.


You are right, if the calculated load isn't more than what 4/0 aluminum is rated for at the 60 degree chart.


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## Lythropus (Jan 27, 2009)

I don't have the calcs in front of me but the house didn't even need a 400 amp service we just like to make sure they have plenty of room to grow on larger homes, and we split up large rooms alot into lighting loads and rec loads so we end up with alot of circuits...


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## william1978 (Sep 21, 2008)

Lythropus said:


> so what does everyone else use for the mast and feeders to the panels on a 400 amp?


3/0 copper paralleled twice. Around here the power company will run the riser, but most of the time the electrician installs it. Is it that way in other parts of the country?


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## cobra50 (Aug 12, 2009)

heel600 said:


> Shows you what I know.
> 
> I thought you size service conductors based on the calculated load.


Did you exceed the four conductor limit?


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## Little man (Jul 20, 2009)

310.4 (a) say that I can parall 4/0 And 310.15 say that parlled 4/0 can be used for a 400A dwelling service, 310.15(4)) say that a neuteral that carries only the unbalance current from other conductors of the same circuit shall not be required to be counted Also in 310.15(B)(6) chart says that paralled 4/0 is the same as 600 mcm any way the wire will carry the same load


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## Lythropus (Jan 27, 2009)

Little man said:


> 310.4 (a) say that I can parall 4/0 And 310.15 say that parlled 4/0 can be used for a 400A dwelling service, 310.15(4)) say that a neuteral that carries only the unbalance current from other conductors of the same circuit shall not be required to be counted Also in 310.15(B)(6) chart says that paralled 4/0 is the same as 600 mcm any way the wire will carry the same load


yes but paralleled 4/0 alu up a mast is 6 conductors 4 of them load carrying which he is saying I have to derate according to 310.15(b)(2)(a) at 80% with between 4 to 6 load carrying conductors


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## Lythropus (Jan 27, 2009)

they make us run the riser


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## Magnettica (Jan 23, 2007)

I don't know why the inspector failed you here. Table 310.15 (B)(6) specifically states 4/0 Aluminum is good for 200 amps, so why wouldn't the same amperage apply in parallel if you have followed the guidelines laid out in 310.4? Derating should have nothing to do with it if you don't have more than three current carrying conductors in each conduit.

You did run 2 separate conduits on the line of the meter right?


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## Magnettica (Jan 23, 2007)

> _I ran a 3 1/2" pvc mast about 8 feet or so with paralleled 4/0 alu up the mast._



So you have all (6) conductors up one conduit? Now I know why your inspector failed you. That's 6 CCC's (current carrying conductors) in 1 conduit. Table 310.15 (B)(2)(A) ranks those 6 conductors to be derated by 80% of the ampacity listed in table 310.16, not 310.15 (B)(6). 

The ampacity of 4/0 aluminum per 310.16 is 150 amps. 

150 amps X .80 = 120 amps.

120 amps X 2 = 240 amps.

So what you thought was a 400 amp service is really only good for 240 amps. You need to run a 2nd conduit so you don't have to derate and can actually use table 310.15 (B)(6) for your 400 amps. 

Good luck.


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## Magnettica (Jan 23, 2007)

Btw, got any pictures of that massive service head with all the conductors pouring out of it? :lol:


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## MDShunk (Jan 7, 2007)

Magnettica said:


> Btw, got any pictures of that massive service head with all the conductors pouring out of it? :lol:


I have one for you. Made by a sheet metal shop:


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## user4818 (Jan 15, 2009)

MDShunk said:


> I have one for you. Made by a sheet metal shop:


I'm guessing this was a mill or similar building that was decomissioned, and the power needs are just to keep a few lights and receptacles live now...so the poco downsized the service.

Is this corner grounded delta?


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## william1978 (Sep 21, 2008)

Did it have a 3rd party label on that weather head?


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## MDShunk (Jan 7, 2007)

william1978 said:


> Did it have a 3rd party label on that weather head?


No, nor is it required to. It was made in a UL panel shop, so it could have had one. Probably would have added a few bucks for a sticker.


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## MDShunk (Jan 7, 2007)

Peter D said:


> I'm guessing this was a mill or similar building that was decomissioned, and the power needs are just to keep a few lights and receptacles live now...so the poco downsized the service.
> 
> Is this corner grounded delta?


No. Condo conversion. The w/h is new. It was temp'd in with the old drop, since there wasn't much going on inside yet.


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## user4818 (Jan 15, 2009)

MDShunk said:


> No. Condo conversion. The w/h is new. It was temp'd in with the old drop, since there wasn't much going on inside yet.



Ah right. So you installed that monstrosity? :laughing: I'm surprised the poco allowed overhead for a service that large. Clearly there are extenuating circumstances for its existence.


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## Magnettica (Jan 23, 2007)

MDShunk said:


> I have one for you. Made by a sheet metal shop:


Right, that was my point that they you can't go down to the local Cooper Electric Supply and buy a service head for 6 SEC's.


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## froggie9189 (Aug 19, 2009)

why not bring your feed in with 3/o copper and use 4/o al to feed your panels.. or did i miss sumthin'. shut up NolaTigaBait, you're still mad at me over that silly panel. was that a real pic of the meter can? if so, cooool!!!!


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## froggie9189 (Aug 19, 2009)

Grandfather is a scary old fire hazard. but, work with what you got! make sure they understand existing, right?


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## Lythropus (Jan 27, 2009)

We ended up running 600 alu up the mast in the same 3 1/2" pipe, but they failed it again because my house was originally rated for a 180 amp service with a piece of #4 copper as the ground conductor to the ground rod. I forgot to resize it for the 600 up the mast, so I went back again and sized it correctly to 1/0 Copper (My fault I honestly just forgot it). Then he failed it again saying I needed 24 feet to the top of the weatherhead and that 600 needs a larger size conduit??? 24'? 600 doesn't use 40% pipe fill in a 3" pipe, let alone a 3.5". I'm seriously done messing with it...I'm going to rip if off, replace the vinyl and run it underground, let the poco mess with the wire...

I didn't run 3/0 copper up the mast because the power company said they wouldn't hook to it. The inspector said it was fine but they are two completely seperate things. I don't know how it works for some of the other states but even if it passes the county/city inspector here the power company can still turn it down...

He won't give me an actual piece of paper saying what he wants and why it failed...normally a red card says exactley what's wrong but apparently that's not the case here.


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## froggie9189 (Aug 19, 2009)

have you tried to go over his head and talk to the chief inspector? I've had good experiences with mine. He has the power to make an exception.


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## froggie9189 (Aug 19, 2009)

sorry... I read that fast. Call the head of your poco engineers and see what he says. Same deal, he can make an exception. by the way, his name is sir.


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## froggie9189 (Aug 19, 2009)

my poco is the same evidently, they can turn down a hook up that is within code beacause the engineer can't figure something out.


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## Jim Port (Oct 1, 2007)

Lythropus said:


> We ended up running 600 alu up the mast in the same 3 1/2" pipe, but they failed it again because my house was originally rated for a 180 amp service with a piece of #4 copper as the ground conductor to the ground rod. I forgot to resize it for the 600 up the mast, so I went back again and sized it correctly to 1/0 Copper (My fault I honestly just forgot it).


Perhaps he forgot that to the rod never needs to be larger than #6?


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