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#188600 - 08/19/09 11:48 PM service conductor options  
mr_electrician  Offline
Member
Joined: Jun 2007
Posts: 106
London, Ontario
Hi, I have a 2" pvc conduit that runs from 200A meter base to interior basement wall. I have the 2" pvc conduit under the garage pad and comes up above the pad before going over foundation into panel. There are 3 90's in the run and I am going to pull 3/0 RW90 copper. I know I can use 2/0 if I want to. Just curious what others would use in this set up?


Never trust an electrician with no eyebrows!!

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#188607 - 08/20/09 02:21 AM Re: service conductor options [Re: mr_electrician]  
twh  Offline
Member
Joined: Mar 2004
Posts: 915
Regina, Sask.
You need an insulated ground and neutral per 10-806(5) and 10-808(3). Aluminum is cheaper and easier to handle. Using oversized wire increases the required size of bonding and grounding conductors in Tables 16 and 17.

I had an instructor explain wiring above code. He said that the length of wire out of a service head is minimum 30 inches. 3 feet won't be rejected, but it isn't better. It's just a waste of money and material.


#188629 - 08/21/09 10:01 AM Re: service conductor options [Re: mr_electrician]  
brsele  Offline
Member
Joined: Jul 2008
Posts: 91
Northern Ontario
Originally Posted by mr_electrician
Hi, I have a 2" pvc conduit that runs from 200A meter base to interior basement wall. I have the 2" pvc conduit under the garage pad and comes up above the pad before going over foundation into panel. There are 3 90's in the run and I am going to pull 3/0 RW90 copper. I know I can use 2/0 if I want to. Just curious what others would use in this set up?


I wasn't aware that you could use RW90 underground, so I looked it up on the Nexans website and son of a beech, you can. Thanks for the info.

As for options,you can use T90 (then you will need 3/0) or USEI (here you'll need 4/0). You can also reduce the size of your neutral. How long is the run? Why do you want to oversize the conductors?

BTW, in Ontario we don't run a bonding conductor between the meter base and the panel.

Bruce


#188632 - 08/21/09 02:49 PM Re: service conductor options [Re: brsele]  
mikesh  Offline
Member
Joined: Jun 2006
Posts: 613
Victoria, BC, Canada
Brsele
T-90 is not approved in Canada for wet locations. I know the US has thwn and thhn which are similar to t90.
It is not therefore approved for installation underground per table 19. Use RW or TW underground.
The placement of a bonding conductor in PVC for services or sub services can get accepted and rejected in BC. A previous codes interpretation guy for the BCSA's predecessor made it policy to require a bonding conductor in all PVC raceways.
In the current BCSA and here in Victoria I think most inspectors would not require a bonding conductor between the meter base and the panel as long as the grounding is done in the panel. If you installed a duplex meter and grounded in the meter base then you would have to install bonding conductors between the meter and panel(s) The other place where you can save the bonding conductor is for a sub feed to an out building where you establish a ground at the out building. IE you use a service entry switch or combo panel, bond the neutral and install a ground electrode. The fault path to the source is the grounded circuit conductor(neutral) A bonding conductor would in this case just provide a parallel return which can impose dangerous voltages on the non-current carrying parts of the system.


#188635 - 08/21/09 07:48 PM Re: service conductor options [Re: mikesh]  
brsele  Offline
Member
Joined: Jul 2008
Posts: 91
Northern Ontario
Mikesh,
T90 and TWN75 are the same thing. At least the T90 that I buy is also marked TWN75. Not that I've tried, but I doubt that you could buy T90 around here that isn't also marked TWN75.
The difference is that when run underground, the cable ampacity is based on 75 degrees C. Which is why I told the OP that he would have to run 3/0.

Can you actually buy T90 in BC that isn't also marked TWN75?

Bruce


#188639 - 08/22/09 12:29 AM Re: service conductor options [Re: brsele]  
twh  Offline
Member
Joined: Mar 2004
Posts: 915
Regina, Sask.
Quote
If you installed a duplex meter and grounded in the meter base...
I've seen that, but I can't find a rule that allows it.


#188664 - 08/23/09 06:12 PM Re: service conductor options [Re: twh]  
mr_electrician  Offline
Member
Joined: Jun 2007
Posts: 106
London, Ontario
Originally Posted by twh
You need an insulated ground and neutral per 10-806(5) and 10-808(3). Aluminum is cheaper and easier to handle. Using oversized wire increases the required size of bonding and grounding conductors in Tables 16 and 17.

I had an instructor explain wiring above code. He said that the length of wire out of a service head is minimum 30 inches. 3 feet won't be rejected, but it isn't better. It's just a waste of money and material.


I do not need to pull a ground here in my area as the neutral is bonded in the meter base. As for the wire I should use, I could used T90 based on TW75 rating. Would be easier to pull through 3 90's in the pvc run. I am trying to figure out if I can use RW90. I think I am confusing rule 6-300. If I read in one way (6-300 (1)(a)) then it tells me I can use RW90 because my 2" conduit is complete from meter base to Lb in garage (wet location). If I read 6-300 (1)(b) then it has to be a single or muti conductor cable approved for use in underground services. I think the OR between the two allows be to used RW90 in the conduit for my underground service cable. Make sence??


Never trust an electrician with no eyebrows!!

#188667 - 08/23/09 10:21 PM Re: service conductor options [Re: mr_electrician]  
twh  Offline
Member
Joined: Mar 2004
Posts: 915
Regina, Sask.
I agree the "or" means RW90 is okay. I don't think you are allowed to pull USEI into a complete conduit run.

The point made by brsele is that if you use T90 with the 75 degree rating, you need a larger conductor. It probably wouldn't be easier to pull.

You're correct about not needing a bond in the conduit. If you use 3/0 cu RW90 with a 210 amp rating, the ground to a water line would have to be #3 instead of #6. I think I remember something about a ground plate never needing more than a #6 ground wire.

Interesting about the T90 in a service. We can't run T90 outside in Saskatchewan because the temperature rating isn't low enough.



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