ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat Box
Recent Posts
Lock-down Thread
by Bill Addiss - 02/27/21 01:16 PM
Northern Tool Recalls Powerhorse Generators
by Admin - 02/25/21 09:49 PM
You will never guess
by gfretwell - 02/25/21 07:48 PM
New tool
by SMOKEYBOB - 02/15/21 04:59 PM
New in the Gallery:
Facebook follies, bad wiring
FPE in Germany pt.2
Who's Online Now
1 registered members (Scott35), 19 guests, and 19 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
service conductor options #188600 08/19/09 10:48 PM
Joined: Jun 2007
Posts: 106
M
mr_electrician Offline OP
Member
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!!
Tools for Electricians:
Re: service conductor options [Re: mr_electrician] #188607 08/20/09 01:21 AM
Joined: Mar 2004
Posts: 947
T
twh Offline
Member
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.

Re: service conductor options [Re: mr_electrician] #188629 08/21/09 09:01 AM
Joined: Jul 2008
Posts: 98
B
brsele Offline
Member
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

Re: service conductor options [Re: brsele] #188632 08/21/09 01:49 PM
Joined: Jun 2006
Posts: 613
M
mikesh Offline
Member
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.

Re: service conductor options [Re: mikesh] #188635 08/21/09 06:48 PM
Joined: Jul 2008
Posts: 98
B
brsele Offline
Member
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

Re: service conductor options [Re: brsele] #188639 08/21/09 11:29 PM
Joined: Mar 2004
Posts: 947
T
twh Offline
Member
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.

Re: service conductor options [Re: twh] #188664 08/23/09 05:12 PM
Joined: Jun 2007
Posts: 106
M
mr_electrician Offline OP
Member
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!!
Re: service conductor options [Re: mr_electrician] #188667 08/23/09 09:21 PM
Joined: Mar 2004
Posts: 947
T
twh Offline
Member
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.


Featured:

2020 National Electrical Code
2020 National Electrical
Code (NEC)

* * * * * * *

2020 Master Electrician Exam Preparation Combos
2020 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Member Spotlight
Posts: 165
Joined: March 2007
Show All Member Profiles 
Top Posters(30 Days)
Popular Topics(Views)
275,531 Are you busy
209,423 Re: Forum
196,814 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.7.3