Wire size for garage

[jimmygmc]

Ok here is my dilemma I have read threads for hours, purchased the electrical code simplified book and talked to numerous people and keep getting different answers. I am going to take 100amps out of the meter base via a double meter base and run it 40' to garage panel in ground. How deep of a trench what wire and size conduit. I was told 2' trench with RW90 3/7 black for hot, RW90 3/0-7 white for common and RW90 6/7 green for ground and 1 1/4 pvc. also 6" of screened sand in bottom of trench and 6" sand to cover conduit. I live in Ont. just out side Ottawa. Will this make electrical inspector happy.

Thanks for comments in advance, Cheers

 

[Aftermath]

Every inspector is different! I would just make a call and ask what they would like to see. No more guess work.

D.

 

[jimmygmc]

Good idea, he is the only guy I didn't ask. Thanks...

 

[LX-Markham]

I dug the trench, but had an electrician do the rest. It involved upgrading the house panel to 200A, then we relocated the 100A house panel to the garage.

Trench was 24" deep. Also ran a gas line and a conduit for a water line.

 

[alfredeneuman]

Ok I was told 2' trench with RW90 3/7 black for hot, RW90 3/0-7 white for common and RW90 6/7 green for ground

The RW90 3/7 is equivalent to a #3 AWG conductor.

If the RW90 3/0-7 is equivalent to a 3/0 AWG it would be WAY oversized. The common wire is referred to as a neutral.

It would make no sense to have a neutral larger than the hots. It would serve no purpose at all.

 

[Trey T]

I think the OP mistyped the wire guage. I think he meant:

Hots: 3-7 (AWG-Strand)
Neutral: 3-7
Ground: 6-7

http://www.southwire.com/ProductCatalog/XTEInterfaceServlet?contentKey=prodcatsheet388

As far as the backfilling goes for electrical conduit, native soil is fine. Engineering specs calls for any types of soil smaller than 3/8" can be use for bedding. JUST TO SIMPLIFY THINGS, JUST GO W/ THE CLEAN NATIVE SOIL.

 

[theoldwizard1]

First, I know nothing about Canadian codes ! Everything I mention needs to be double checked !!

Second, you need to verify that a double lugged meter based is allowed by both the local inspector AND the power company. This is not allowed in many place or only allowed after some kind of disconnect (no, a meter is NOT a disconnect).

Third, 100A is an awful lot for a garage. You can comfortable run a good sized electric heater and 1 or 2 major power tools (welder, compressor, table saw, dust collector) on 60A.

Fourth, another reason why you want a breaker/fuse at the meter (or come off the main panel in the house) is so that you can downsize the wire in relation to the size of the main in your garage panel. If you have a 100A panel, but the disconnect at the meter is a 60A fuse/breaker, you only need wire capable of running 60A. So stick with the 100A panle in the garage but only feed it with (fuse/breaker protected) cable capable of 60A.

In the US, the most "cost effective" cable is Mobil Home Feeder (MHF). It is 4 insulated aluminum conductor and designed for direct burial. 2-2-2-4 would handle 60A. Any thing above ground must be in a conduit, even inside of a building.

Last, 2' is plenty deep. Skip the conduit, but make sure you use a Schedule 80 "sweep" where you transition from underground to above ground.

 

[wildstyle]

I'm in BC, but here it was 18" to top of the wire. I ran Teck90 armored cable (no conduit) it is #1awg aluminum for my 100 amp run.

 

[teamextreme]

US code requires 18" for PVC conduit and 24" for direct bury cable. Sand or similar back fill material is generally not required. Some local municipalities may have rules requiring it, but NEC doesn't require it.