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Deranged1 09-19-2012 07:59 AM

Sub panel and breaker question
Ok, so I am putting a sub panel in my garage. Going to be putting in a 125A max sub panel but only going to run about 100amp. I am run Aluminum 2/3 wire to the sub. I understand the max rating is 95amp for the AL cable. I can't seem to find a 90 amp for a Federal Pioneer Stab-lok style. Can I just install a 100 amp breaker?

Here is a link to the cable.

Product number

rjniles 09-19-2012 08:18 AM

What do you mean by Aluminum 2/3wire? Cable or conduit? Number of conductors? Can we assume the garage is attached to your house?

You linked to the cable after I posted. Noticed you are north of the border: we need a Canadian sparky to show up.

Pretty expensive cable, there are cheaper alternatives available.

Deranged1 09-19-2012 08:24 AM

The cable is ACWU it is Aluminum Cable that is in BX and has a PVC coating on it so it can be directly buried without conduit. It's 2 gauge 3 conductor plus ground. Here is a link to the data sheet.

Deranged1 09-19-2012 09:01 AM

Also in my garage there is currently a fuse box with two 15 amp breakers. Can I have two feeds running to a garage? Or do I need to pull out the current box in there. I really don't need the additional panel with a 100amp panel anyways but I am just lazy.

rjniles 09-19-2012 09:33 AM


Originally Posted by Deranged1 (Post 1012914)
Also in my garage there is currently a fuse box with two 15 amp breakers. Can I have two feeds running to a garage? Or do I need to pull out the current box in there. I really don't need the additional panel with a 100amp panel anyways but I am just lazy.

Under the NEC (and again I am not sure if the CEC differs in this area).

With an amperacity of 95 amps you are allowed to up-size to the next standard breaker size (100 amp).

You are allowed only 1 feeder to a detached outbuilding (that feeder can be a single branch circuit, a MWBC (Multiwire branch circuit) or a (sub)panel feeder.

Deranged1 09-19-2012 09:43 AM

I have talked with an electrician and he said that I can go up to the next size breaker by code. But I just wanted to make sure.

andrew79 09-19-2012 09:47 AM

#2 r90 (90 degree cable) aluminum cable is good for 100a. A 75 degree insulation requires 90a overcurrent protection. Values taken from table 4 in the codebook. Derate as necessary.

Deranged1 09-19-2012 09:52 AM

Thanks Andrew, and as stated above I will need to remove the current panel and feed from the garage. Correct?

andrew79 09-19-2012 11:27 AM

You don't have to but you should. There's a whole slew of grounding you'll have to do for the sub panel as well.

Deranged1 09-19-2012 11:32 AM

Doesn't it just need to be bonded to the main panel with the ground and neutral seperated since there are no livestock in the building?

AllanJ 09-19-2012 12:12 PM

When you have a subpanel in the separate building, it needs a pair of ground rods at least 6 feet apart, in addition to the ground wire accompanying the feed from the main building.

If you run a new (larger) feed to a new subpanel and there was an older (smaller) subpanel then you must disconnect and decommission that smaller feed. Optionally you can connect the older subpanel to a breaker (double wide double pole if 120/240 volts) in the new panel.

Deranged1 09-19-2012 12:14 PM

Hi AllanJ, the Canadian code differs from the NEC regarding sub panels and grounding.

Deranged1 09-19-2012 02:46 PM

Also in Canada, can I run a 100 amp sub panel off of a 200 amp main panel legally?

andrew79 09-19-2012 10:09 PM

you can run that sub off the main no problem.

now i learned something tonight. There's i bit of a grey area in this part of the code and what i thought was the right way to do it apparently isn't. I always thought a sub panel had to not have the neutral and ground bonded but the rule is actually as follows. If the panel is in the same building then the neutral and ground aren't permitted to be bonded. If the sub panel is in an outbuilding then the neutral and ground do have to be bonded at the sub panel. You actually don't even have to run a ground in the pipe with the feeders.

so in your instance you need to drive one ground rod and hook that up to your sub panel with either a number 8 copper or number 6 aluminum. Keep in mind that any ground wire smaller than 6 awg has to have mechanical protection, ie. run in pipe. If you go with the 8 copper then you will have to enclose it in pipe and if you use emt you have to use ground bushings at both ends of the pipe and run the ground through them. If you use 6 gauge aluminum and there's no chance of physical damage then you can run it surface provided it's clipped tight and neat.

If the neutral bar in your sub panel isn't making contact with the metal of the panel then you need to install a jumper between the neutral bar and the ground bar the same size/type as you used to connect to the ground rod.

allan is absolutely right with having to disconnect the old feed, you can leave it installed but you have to pull the cables out of the main panel so there's no chance of having it turned on by accident.

Deranged1 09-27-2012 07:28 AM

So I am trying to figure out how to get my cable into the garage. It'll be coming out of the ground up the outside of the garage and right through the wall. Does it need conduit coming out of the ground? Also the panel will be right on the other side of the wall I am running it into. So it's a 180 degree turn. Can I use to LB connectors to do this? If no conduit is required can I connect the LB connector directly to the armored part of the cable? Also can I run the cables out of the sheathing through the LB connector so it will be easier to flex? Also can I use PVC for the LB's?

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