Review my results and code sections please!

[Strahan]

Situation: A friend of mine is in the process of building a house. This project has been done in steps so the detached garage was built first. Therefore the service was brought into the garage with a 200amp supply and panel. Now he is preparing to build the house and asked me to size his Feeder conductors to the house. He wants to put a 200amp at the house as well.

Here is what I got: Per 408.36 he can size the OCPD in the garage panel at 200amps. Conductor size using table 310.15(B)(6) "conductor types and sizes for 120/240 volt 3-wire single phase dwelling services and feeders" says 2/0 copper for 200amp rating. 310.15(B)(6) points me in a round about way to 250.122 that I'm interpreting a size 6AWG for equipment grounding conductor and neutral size.

So in the long run 2-2/0 and 2-6awg to supply his house is this right? And of course keep egc and neutral seperate at house and planning on driving two ground rods to be safe. Thanks for your help!!

 

[augie47]

Would not work here.
First, the fact that the garage is power off the service would mean the feeders to the house were not carrying the entire load and 310.15(B)(6) could not be used.
Secondly the size of the neutral would have to be calculated and can not be based on 250.166.

 

[Strahan]

Would not work here.
First, the fact that the garage is power off the service would mean the feeders to the house were not carrying the entire load and 310.15(B)(6) could not be used.
Secondly the size of the neutral would have to be calculated and can not be based on 250.166.

Ok than per 215.2(A)(1) I would size to 100% non-continuous and 125% continuous. I don't see anything that constitutes a continuous load so I would go with 3/0 copper. Now I'm not sure of neutral so I know that it is not required to be larger than the ungrounded conductors so that would be 3/0 as well, but I think I can still use 250.122 for my ECG which would still give me a 6AWG. How's this?

 

[Strahan]

Would not work here.
First, the fact that the garage is power off the service would mean the feeders to the house were not carrying the entire load and 310.15(B)(6) could not be used.
Secondly the size of the neutral would have to be calculated and can not be based on 250.166.

Ok did some digging here and I'm not sure if I understand you. 215.2(A)(1) points me to 250.122 to size my grounded conductor. This installation would be considered a feeder. :-?

 

[RETRAINDAILY]

Ok than per 215.2(A)(1) I would size to 100% non-continuous and 125% continuous. I don't see anything that constitutes a continuous load so I would go with 3/0 copper. Now I'm not sure of neutral so I know that it is not required to be larger than the ungrounded conductors so that would be 3/0 as well, but I think I can still use 250.122 for my ECG which would still give me a 6AWG. How's this?

in a 2" conduit looks good
how far?

 

[augie47]

Ok did some digging here and I'm not sure if I understand you. 215.2(A)(1) points me to 250.122 to size my grounded conductor. This installation would be considered a feeder. :-?

215.2 tells us the MINIMUM size, 220.61 addresses calculating the needed size.

 

[RETRAINDAILY]

250-122 is your grounding conductor not your grounded conductor.
full size neutral would be best IMO.

 

[Strahan]

250-122 is your grounding conductor not your grounded conductor.
full size neutral would be best IMO.

Once again 215.2(A)(1) states "grounded Conductor" 215.6-Feeder EGC points me to 250.32(B) which states "The EGC shall be sized in accordance with 250.122" as well.

 

[augie47]

250.122 is fine for the equipment grounding conductor.
215.2 on the grounded states:
The size of the feeder circuit grounded conductor shall not be smaller than that required by 250.122,
which only gives you the minimum size. It does not give you the size required to carry the load. That must be calculated.

 

[RETRAINDAILY]

oh, now matter what you calculate your neutral, say 30 amp, it still can not be smaller than a 6 AWG is what I get out of that.

 

[augie47]

if its a feeder, yes

 

[Jim W in Tampa]

Why not save some money and use aluminum. Likely with most houses 70 % of that 200 will likely be enough for neutral but if run is long i would not down size.

 

[Strahan]

Why not save some money and use aluminum. Likely with most houses 70 % of that 200 will likely be enough for neutral but if run is long i would not down size.

Run is fairly long. I will not down size but I'm still a little confused according to Augie you always have to calculate neutral. Not sure if I'm following. Why have it in 215 then?

 

[RETRAINDAILY]

op says "he wants to put a 200amp"
Have you calculated the house you will need all that info to calculate the neutral.
if you up size the feeder you will probably need to up size the neutral perspectively

 

[augie47]

lets assume you had no 240 volt load and the 120 volt load was 150 amps...
how much current would the neutral need to carry ?

It was discussed a lone time why there was a minimum on the neutral of a feeder and I think the consensus was in case there was a neutral to feeder phase short..but regardless..

any conductor must be size to the calculated load....

215.2 is the MINIMUM... it is not necessarily what is needed to carry the load.

 

[Strahan]

lets assume you had no 240 volt load and the 120 volt load was 150 amps...
how much current would the neutral need to carry ?

It was discussed a lone time why there was a minimum on the neutral of a feeder and I think the consensus was in case there was a neutral to feeder phase short..but regardless..

any conductor must be size to the calculated load....

215.2 is the MINIMUM... it is not necessarily what is needed to carry the load.

Ok I agree with you Augie, but as you stated 215.2 is the minimum which meets code coorect? Now before we get to far I'm planning on running same size neutral, but how would an inspector fail an installation per 215.2? I don't believe he would do a calculation if he did it would be the first time I witnessed it.

 

[ty]

Ever been to Turbotville?

Anyway, where is this 200 amp feeder originating??

 

[Strahan]

Ever been to Turbotville?

Anyway, where is this 200 amp feeder originating??

Yes I have! I only live 2minutes from Turbotville. The 200amp feeder will be originating from the 200amp panel in the garage. I have'nt checked into the availability of a 200amp breaker for this panel nor do I know if its a feed through I have to check on this. I live on the East end of 8th Street Watsontown.

 

[ivsenroute]

If his permit was pulled prior to Jan 1, 2010 then the 2005 NEC applies, not the 2008 as an FYI.

 

[ty]

Yes I have! I only live 2minutes from Turbotville. The 200amp feeder will be originating from the 200amp panel in the garage. I have'nt checked into the availability of a 200amp breaker for this panel nor do I know if its a feed through I have to check on this. I live on the East end of 8th Street Watsontown.

My nephew lives in Watsontown.

Anyway, What brand of 200amp panel is there?
If this is a residential loadcenter, i have a high doubt that it is a feed-thru type. I also doubt that you will get a 200amp snap in breaker that it readily availible.
You are probably looking at a 125amp max snap in.

That would change how you have to go about this install.
Can the meter socket be changed to one that has double lugs on the load side?