Another electrical service to barn question

[Jason641]

I am in the process of building a pole barn approximately 300' behind my house. I have 4/0 AL direct burial wire that I will use to go from the house to the barn. I have done some research on how best to do this but I am still confused on a couple things, it seems that there is a ton or different ideas on the proper way to do it. I am sitting here looking at the 2008 NEC and having a hell of a time figuring out what applies to my situation. I want to have a 100 amps to the barn.

At the house I have underground wire coming from the pole at the street to my meter on the side of the house. There is a 200 amp disconnect at the meter because my main panel is inside the house about 30 feet from the meter location. Inside I have a 200 amp panel that has a 200 amp main disconnect.

First question(s) is where is the best place to get power from for the barn?

Option #1: Can I add a second disconnect (100 amp) attached to the meter base outside and run the wire from there to the barn? How would I add a second disconnect, as the main 200 amp disconnect is a part of the meter base and is connected by solid bars inside? Do I need a disconnect for the barn at that location (house) or can I just connect the wires in there and have a disconnect at the barn?

Option #2: Somehow fight the 4/0 wire into the main panel in the house and attach it to a 100 amp breaker. 4/0 probably won't fit in a 100 amp breaker, is there a solution for this?


Second Question(s) are about connecting it to the panel in the barn.

Do I leave the ground and neutral bars bonded or un-bonded. I will drive 2 ground rods at the barn and tie them to the panel. I will have a water line going from the house to the barn but it is plastic pipe so I shouldn't have any other "metallic connections" between the house and barn.

I will probably use a 200 amp panel in the barn just for ease of connecting the wires.

 

[Aceman]

Is it possible to have the power co. run a second service to your barn?

 

[Jason641]

It is a possibility but I would rather not, for the little bit that I will be using the power out there I'd rather not have to pay for a separate service. not to mention they would have to set another pole somewhere in my yard etc...

 

[trbomax]

There are several options here. In my case,I have a 400a service drop at my shop,and installed a feed thru panel as the main disconect.The ground rods are at that location. From the bottom of this panel, 3-4/0alum and 1-4 cu feed the subpanel,that is my house service. There are also 3-100a 2pole breakers in the main that feed the horse barn subpanel,one is dedicated to my welders (another 100a subpanel) and one feeds the shop.They are all fed with 2-3 w/ground.

Now if you use your house as the main disconect and feed the shop from it to a 100a subpanel , you will need 4 conductors. What you can do is mount a 12x12 box onto your house panel. Run the 4/0 into that. Then run #2 from the 100a breaker into it as well. Splice the #2 and 4/0 wire in that box with split bolts. This way you can use the 4/0 to minimize voltage drop and connect to the 100a breaker in your panel. You will have to install a bonding strip in the shop panel for all the bare wires as these cannot be ganged up with nuetral in a subpanel.Do not install the green screw in the pubpanel.

The only other way is to change your house panel to a feed thru panel,then you can attach the 4/ directly too it w/o a breaker.The disadvantage with that is that when (if ever) you have to work on the line feeding your shop,you will have to kill the house main.

 

[Jason641]

Thanks, I think that will work out great, I didn't know I could tie the wires together like that. I have fully wired 4 different houses, some sub panels, and multiple additions/basements and all have passed inspection but I have never added power to an outbuilding like this so I was a little bit confused.

Do I still need the ground rods at the barn if I have the neutral and ground separate in the barn panel? It seems like I should but you didn't mention it.

Again, thanks for the help.

 

[walrus]

Do I still need the ground rods at the barn if I have the neutral and ground separate in the barn panel? It seems like I should but you didn't mention it.

Again, thanks for the help.

Yes you do

 

[trbomax]

In your case you do,but do not tie the ground in any way to the nuetral,and even with the ground rods,you still need the 4th ground wire.As a general rule,if the buildings are more than 100' apart,you need the additional rods at the subpanel location.
The split bolts will need anti ox paste and need to be taped with a heat shrinkable or rubber tape,then taped with 33+,in addition I would color code them when finished with red and white tape before the splice.

 

[mrb]

In your case you do,but do not tie the ground in any way to the nuetral,and even with the ground rods,you still need the 4th ground wire.As a general rule,if the buildings are more than 100' apart,you need the additional rods at the subpanel location.
The split bolts will need anti ox paste and need to be taped with a heat shrinkable or rubber tape,then taped with 33+,in addition I would color code them when finished with red and white tape before the splice.

where does this 100ft rule come from? If you have a detached structure, it needs a groundign electrode whether its 10 feet or 1,500 feet away.

With regard to split bolts, no one really uses those anymore, look into polaris blocks.

Another thing to remember, when upsizing conductors for voltage drop (ie using 4/0 on a 100 amp circuit) you also have to increase the ground. Cant use three 4/0 and a #8 for example.

 

[trbomax]

where does this 100ft rule come from? If you have a detached structure, it needs a groundign electrode whether its 10 feet or 1,500 feet away.

With regard to split bolts, no one really uses those anymore, look into polaris blocks.

Another thing to remember, when upsizing conductors for voltage drop (ie using 4/0 on a 100 amp circuit) you also have to increase the ground. Cant use three 4/0 and a #8 for example.

In my county thats the way it is.

Split bolts are how the inspecter guy said to do it,so thats what we got. (edit) I did not change wire sizes on any runs. What I DID do was change the location of the panel in the horse barn after the wire was run.I got ahead of myself and put the supply wire in as the building was going up. 3 months later I had to change the "plan". I went to see him about it because I needed 20 more ft , so he allowed me to do the 12x12 box and split bolts to get to the new location.All of this was in pipe.

That makes sense.

 

[Charles (in GA)]

Can I add a second disconnect (100 amp) attached to the meter base outside and run the wire from there to the barn? How would I add a second disconnect, as the main 200 amp disconnect is a part of the meter base and is connected by solid bars inside? Do I need a disconnect for the barn at that location (house) or can I just connect the wires in there and have a disconnect at the barn?

Does your outside disconnect have provisions for other circuit breakers? If it does, put in a 100 amp and go from there. You will need to splice on smaller wire to connect to the 100 amp breaker in any case.

Its possible, but not probable, that the meter socket has an extra set of lugs you can tap off.

I would not take the 4/0 inside. I would connect a more reasonable size wire capable of the 100 amps (proper splicing inside a box at the foundation) and carry the smaller wire inside to the main panel if you have to go that route.

I'm assuming you already have the 4/0 is why you want to use it.

Charles

 

[Jason641]

Thanks everyone for all the help.

Charles,
Yes, I already have enough 4/0 to make the ~330' run, that's why I'm using it, plus with the distance it will help minimize voltage drop. I don't remember the meter socket having an extra set of lugs when I put it in (it's been 4 years though so I could be wrong).

 

[Jason641]

I want to make double sure I have this straight. As I said before I have the 4/0 wire (3 conductors) already. I don't have the 4th wire for the ground, or the downsized wire that I will use for the first couple feet out of the panel in the house.

Looking at NEC 250.66, I have 4/0 AL so I need #2 AL for the ground, correct?

For the first 10 feet or so out of the house panel until I splice into the 4/0 I should be able to use #1 AL conductors with a #6 AL Ground using NEC 310.16 75° column in conduit for 100 amp.

I will splice the wires in a junction box with Polaris ISR250 or something similar.

At the panel in the barn I will use 8 AWG copper to tie it to the ground rod at the barn.

Does all this sound good?

 

[Jason641]

Life got in the way so the barn project has been sitting half finished for almost 2 years. I am finally ready to finish it. I want to re-visit my questions from my previous post in this thread as quoted below.

I also have a couple extra questions that I didn't think of when I posted previously:

Is it OK to splice AL to CU wire in the junction box where I will be reducing from the 4/0 to the downsized wires from the 100A breaker using a polaris splice connector? Or should I stick with AL all the way to the breaker? Should I use a 90A breaker and 2-2-2-4 AL from the house panel to the Junction box where I convert it to 4/0 AL?

I want to make double sure I have this straight. As I said before I have the 4/0 wire (3 conductors) already. I don't have the 4th wire for the ground, or the downsized wire that I will use for the first couple feet out of the panel in the house.

Looking at NEC 250.66, I have 4/0 AL so I need #2 AL for the ground, correct?

For the first 10 feet or so out of the house panel until I splice into the 4/0 I should be able to use #1 AL conductors with a #6 AL Ground using NEC 310.16 75° column in conduit for 100 amp.

I will splice the wires in a junction box with Polaris ISR250 or something similar.

At the panel in the barn I will use 8 AWG copper to tie it to the ground rod at the barn.

Does all this sound good?

 

[pattenp]

I want to make double sure I have this straight. As I said before I have the 4/0 wire (3 conductors) already. I don't have the 4th wire for the ground, or the downsized wire that I will use for the first couple feet out of the panel in the house.

Looking at NEC 250.66, I have 4/0 AL so I need #2 AL for the ground, correct?

For the first 10 feet or so out of the house panel until I splice into the 4/0 I should be able to use #1 AL conductors with a #6 AL Ground using NEC 310.16 75° column in conduit for 100 amp.

I will splice the wires in a junction box with Polaris ISR250 or something similar.

At the panel in the barn I will use 8 AWG copper to tie it to the ground rod at the barn.

Does all this sound good?

You need to size your wire based on the 60 degree column. Than would be 1/0 AL for 100A.

 

[pattenp]

Life got in the way so the barn project has been sitting half finished for almost 2 years. I am finally ready to finish it. I want to re-visit my questions from my previous post in this thread as quoted below.

I also have a couple extra questions that I didn't think of when I posted previously:

Is it OK to splice AL to CU wire in the junction box where I will be reducing from the 4/0 to the downsized wires from the 100A breaker using a polaris splice connector? Or should I stick with AL all the way to the breaker? Should I use a 90A breaker and 2-2-2-4 AL from the house panel to the Junction box where I convert it to 4/0 AL?

Again you need to use the 60 degree column when sizing wire for feeders. 2-2-2-4 AL is good for 75A. You'd need to use at least #1 AL for 90A.

 

[PRH44]

The polaris connector you called out is rated for AL dn CU so it would be fine for connecting Aluminum to copper.

Your equipment ground wire would be selected from table 250.122 which is based on the breaker size. Table 250.66 is for grounding electrodes or main bonding jumpers based on wire size. 100 amps would be a #8 copper or #6 aluminum using table 250.122. You may use larger. You are required to adjust your equipment ground size if the phase conductors are increased for voltage drop so you are fine with #2

pattenp in all do respect if he is using individual conductors rated at 75 degree and terminate on a 60/75 degree breaker he would be permitted to use the 75 degree rating.

2011 code cycle also allows the use of the 75 degree column for type SE cable only, USE falls under the 60 degree limitation of 340.80 as pattenp mentions in his post below.
If you use romex you would be required to use the 60 degree column on breakers rated 60/75 degree

 

[pattenp]

PRH44 - In all due respect to you too, but I think you are reading the 2011 code incorrectly. When looking at 338.10 (4) (a) which applies to interior installation of SE, not USE, is where the 60 degree rule applies when installed in insulation. If you look at 338.10 (4) (b) which is for exterior installations, which includes USE for underground installations, must also meet the requirements of part II of article 340. Article 340.80 requires 60 degree. Article 340.80 is excluded in 338.10 (4) (a) so it doesn‘t apply to SE. Code just as in law is subject to interpretation. If you can cite me a code section showing where I’m wrong then please do. The last thing I want to do is give out misinformation.

 

[Norcal]

It does not matter for what reason a wire size is increased, voltage drop, or it's whatever was on the truck, no matter what the reason, the grounding conductor MUST be increased in size, here is a copy & paste from the 2011 NEC...


250.122(B)


(B) Increased in Size. Where ungrounded conductors are
increased in size, equipment grounding conductors, where
installed, shall be increased in size proportionately according
to the circular mil area of the ungrounded conductors.

A few code cycles ago, it was just for voltage drop (VD), but VD was dropped as the only reason that the EGC had to be increased in size.

 

[Jim Johnstone]

The only other way is to change your house panel to a feed thru panel,then you can attach the 4/ directly too it w/o a breaker.The disadvantage with that is that when (if ever) you have to work on the line feeding your shop,you will have to kill the house main.

If he used a feed through lug main panel, directly into a disconnect, then off to his barn, he wouldn't have to kill the power to his house to service the line to the barn.

 

[PRH44]

PRH44 - In all due respect to you too, but I think you are reading the 2011 code incorrectly. When looking at 338.10 (4) (a) which applies to interior installation of SE, not USE, is where the 60 degree rule applies when installed in insulation. If you look at 338.10 (4) (b) which is for exterior installations, which includes USE for underground installations, must also meet the requirements of part II of article 340. Article 340.80 requires 60 degree. Article 340.80 is excluded in 338.10 (4) (a) so it doesn‘t apply to SE. Code just as in law is subject to interpretation. If you can cite me a code section showing where I’m wrong then please do. The last thing I want to do is give out misinformation.

Great catch pattenp USE in fact falls under 340.80. Thank you!

 

[Aceman]

If he used a feed through lug main panel, directly into a disconnect, then off to his barn, he wouldn't have to kill the power to his house to service the line to the barn.

What kind of servicing do you figure the "line" is going to need?

 

[Jason641]

Last Question... I think ... The downsized cable I got to hook into the main panel in the house is 2 awg AL USE-2/RHH/RHW-2 Do I have to have this in conduit from my junction box to the breaker / main panel? It will all be run behind the wall inside the house. I have read that it is 2 hr fire rated and whatever else but nothing that tells me it definately has to be in conduit. I forgot to look at the NEC before I left work (not that I would understand it or look in the right spot).

 

[Aceman]

Do I have to have this in conduit from my junction box to the breaker / main panel?

Yes.

An easy rule of thumb to remember is, if they're individual wires they need conduit. A cable assembly(with multiple wires) with an overall outer sheath usually does not.

 

[pattenp]

Not to cause trouble, but why did you get USE to go from the junction box to the main panel? If you used SE you wouldn't have to put it in conduit.

 

[Jason641]

Not to cause trouble, but why did you get USE to go from the junction box to the main panel? If you used SE you wouldn't have to put it in conduit.

Good question ... I'm not really sure. I don't think there was 4 wire SE available in the size I wanted when I went to get it (at least I don't remember seeing it.) I should have gone to the electrical supply house, but I always end up getting home after they are closed. I have some conduit laying around so its not too big of a deal, I may see if I can grab some SE though to make life a little easier.

Thanks for the responses.

 

[pattenp]

Jason641, not to cause you any headaches. I didn't think about this when I asked about the USE vs SE. Do you realize that USE is not approved to be used in the interior whether it's in conduit or not? I think USE-2 or RHW-2 is ok for interior. This has come up in the post "What do Run to Sub Panel".

I just found some info that indicates USE-2 is not suitable for interior uses.
http://www.iaei.org/magazine/2007/0...-use-cable-be-used-inside-for-premise-wiring/

 

[Jason641]

pattenp, thanks for the heads up, I have heard that before just slipped my mind I guess ... Thanks for the link to the article, I suppose I don't fall under the "except for termination at the service equipment or metering equipment" category? The wire I have is labeled "USE-2 / RHH / RHW-2". I guess I'll have to go get some SE cable.