Virgin Shop Episode 2 - Long Winded

[Mike Flood]

I’m slowly getting a shop set up in the garage and I have wiring questions. Per posts a few weeks ago, I decided to put a 60-amp service in the garage. I ran NMD 6/3 through a finished ceiling (oh, what fun) and dug a trench from the house to the garage (oh, my, even more fun) and ran TEK (TEC?) 6/3 cable (armoured, water proof, withstands nuclear explosions, etc) from the house to the garage. The average depth of the trench is 20 inches but in one spot the cable may be only 15” deep. Total run is about 100 feet, 50 inside and 50 outside.

The first question deals with the NDM 6/3. I was able to fish it through the ceiling with minimal holes. The holes are all 8 X 8 and take those plastic access panels – so I can always get at the cable. The cable is fastened to the joists where there are holes but just lies on top of the drywall between access panels. Is this the right way to do it? Should I have used armour on the inside run? I’m trying to do minimal damage to the ceiling.

Question two is about grounding the sub panel. The code is vague about whether I have to do this or not (if livestock is kept in the shop it must be grounded but there are no future plans to buy cows – besides, it’s hard to fit them on a lathe J). Am I better off to have a separate ground or just use the ground from the house (in the 6/3 cable)?

The third question is on getting a permit. I’ve heard arguments for and against getting a permit. If I take out a permit my fears are the inspector will force me to rip apart the whole ceiling to strap the cable and dig up the trench to insure the cable is deep enough and continuous. My fear about not taking out a permit is it may cause an insurance problem later on if there is ever a fire – either related to the wiring or not. Thoughts?

Sorry to be so long winded.

[Dave]

Hi Mike.

First of all, I would DEFINATELY take out an electrical permit. It would be highly unlikely that the inspector would make you tear the whole ceiling apart. (only if broke some serious codes)
Armoured cable would have been the preferred cable to use however, NMD should be ok as long as it's not laying against anything metal or ran through a joist span used for cold air return.
The inspector will want to see a portion of the trench open to verify (probably just 1 end for 3-4 feet).
AS far as the grounding, the ground in the cable will be sufficient but there is one thing you must concern yourself with. The electrical panel in your house will have the neutral buss (the terminal strip for all the white wires) grounded along with the metal box itself. You must make certain that the new panel in the garage has the neutral buss isolated. (not grounded) Only the metal casing of the panel is to be grounded.
Ther are a few different ways the manufacturers ground the neutral buss.

1. A green or bare wire jumper factory installed from the neutral buss to a lug attached to the panel housing.

2. A flat metal strap attached in the same manner as above

3. A brass screw attached through the buss bar, passes through the isolation block(usually plastic)and is tapped directly into the panel housing.

In any case, these items must be removed before attaching the ground wire to the panel housing.

Good Luck!

Dave

Mike, I forgot to mention, if you have natural gas, propane and/or copper or metal water lines in your shop, they will need to be grounded back to the panel housing (in shop) as well.

[Mike Flood]

Dave, thanks for the great response. I must say that getting a permit was my intention, some friends were saying it was more hassle than it's worth.

I didn't know about isolating the neutral on the sub panel. I'll look for that. The NMD may cross a cold air return - would that require armour or is it not allowed at all?

There's no gas, etc., in the garage that needs grounding. I plan to use electric heat (R40 in the ceiling, R12 in the walls, R7 in the big door) it may be more expensive to operate than gas but installation costs are a lot lower. I haven't run the numbers but "Wet Coast" weather is not like back on the Prairies so I think it's a toss up.

Thanks again.

[Doug Knight in Little Spa]

I feel comfortable in consulting our local inspector before I start a job I've never done before. I do my reading first and go to him with my plan for his comments. I have always found this works well if you go with the attitude that you want to do the job properly.

In your case you might wish to try out your design with the inspector as if you haven't done it yet. For example, if the cable is supposed to be down two feet, you would tell him that you would hit solid rock at 15 inches and see what alternatives he suggests for for reinforcement.

In the end you'll be left to decide if you can go ahead with inspection, make modifications, or not have it inspected and sleep a little more uneasily.

I think it's fair to say that if a fire were shown to be caused by your non-inspected electrical installation, your insurance company likely wouldn't pay. I don't think a fire is likely, but is it possible that a future owner of your property might dig a hole to plant a tree and hit your line with a steel shovel or someone drill into the cable that's sitting on the ceiling?

[Keith in Brantford]

Having been in the fire service for more years that I wish to count I can tell you that your insurance company will pay for a fire if it is caused by wiring that you have done yourself that was not inspected. Insurance companies almost every time pay for fires caused by building owners. In actual fact most fires are caused and very few are accidental.HOWEVER,I am sure that you will sleep a lot better knowing that all is safe with your wiring-- both for now and in the future.
HAVE IT INSPECTED. The last I heard --at least here where I live-- underground wires need to be at least 18" deep and covered with a PT 2"x6".
my$.02
regards keith

[Mike Flood]

Thanks for your responses....Shaw Internet was down over the last day or so hence my late response. I'll let you know how I make out with the inspectors.

Thanks for the comment on insurance vs permits. I always wondered about that.