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-   -   Bizarre Workshop Wiring (http://www.diychatroom.com/f18/bizarre-workshop-wiring-13079/)

slakker 11-05-2007 03:10 PM

Bizarre Workshop Wiring
 
I bought this older home that has a pretty big (12x24) workshop that the previous owner had built. I've been using it myself for a few years and it's fed by an overhead supply line.

I'm needing to reroute that to be a direct burial cable so I started looking into how they had fed it... here's the wierd part...

They took a 220 volt circuit, (2 wire plus one ground) from the main panel to the shed. In the shed, they put in 2 new grounding rods and tied the 2 ground wires together through a large fuse on/off switch/panel.

The outlets and fixtures in the shed have seperate neutrals, etc. that are then tied to the ground via the switch/panel in the shed. So now the shed has 110V circuits. ie; they use the hot from each leg of the main panels 220V circuit and run that to ground via the neutral.

Obviously, everything "works", but is this optimal or to code in Canada? Or when I re-route the overhead, should I run new 3 wire ciruit to the shed?

I hope I explained it well enough....

goose134 11-05-2007 06:02 PM

I can't be sure but this is a good way to find out if what I'm thinking is actually happening. Turn on the lights, and plug something into a couple of outlets and let them run. Then take an amprobe and take a reading on your ground. Just curious.

slakker 11-05-2007 10:09 PM

No amperage on the ground as far as I can tell... I used one of those induction type amp meters... Ground is connected to "ground" via 3 seperate points at the switch/panel... To the Main Panel in the house via the 2 wire and 1 ground wire and also to the 2 grounding rods...

There's obviously current going back on any of the individual neutral returns...

goose134 11-05-2007 10:14 PM

Well, it sounds like you are fine. The way you described the incoming feed, I was concerned that they used the ground as a neutral. But re-reading your post it sounds like the neutral is derived seperately at the shed. It seems like it should be ok. Anyone else?

jogr 11-06-2007 11:51 AM

It doesn't sound fine to me. First, you should have two hot wires, 1 neutral and one ground coming from the main panel and going to the subpanel in the shed. The neutrals should be on a seperate bar than the grounds in the subpanel and the neutral and ground bar should not be bonded to each other. The ground rod at the shed should go to the ground bar in the subpanel. But I really don't understand what you are saying with your wiring description. You seem to be confusing neutral with ground.

Fir

slakker 11-06-2007 01:32 PM

I was hoping to be more articulate... imagine what you've described but no neutral back to the main panel PLUS the neutral and ground are bonded together at the sub panel/switch.

You mentioned neutral and ground should NOT be bonded together... why? It's already bonded in the main panel... is there a ground loop issue I should consider?

However, my real question is more around what are the safety concerns and issues. The long term solution is to re-run the whole circuit, just want to get a sense of what type of priority this is given all the other stuff I have to fix up in this "frankenstien" of a house... :(

NateHanson 11-06-2007 02:12 PM

Sounds like a normal 3-wire service to a detached building sub-panel. If there are NO other metallic connections to the main building (copper water pipe, cable, telephone wire, etc) then my understanding is that it's an allowable way to wire a subpanel. I hear that in 2009 it will no longer be allowed for new installations.

If you wanted to "update" it, or if you have a copper water pipe going out there or something, then you just need to pull a ground wire out to the garage, hook all white wires to the neutral bar, all greens/bare to a ground bar, and then remove the screw that bonds the neutral buss to the box case. That way ground and neutral will be separate all the way back to the house. You still need the ground rods, but they should be attached to the ground bar in the sub.

I'm not a pro, so take my advice with a grain of salt, but it sounds to me like a safe 3-wire installation, from what you've said.

Edit: I just noticed that you plan to convert this to an underground feed. In that case I'd definitely just run 4 wires, and separate ground and neutral in the sub, as I described above. It's safe the way it is now, but for the cost of one more wire, I'd definitely update it so you don't have to worry about future expansions.

jogr 11-06-2007 02:19 PM

I guess you were articulate - I just couldn't believe what I was reading. So they used the ground wire to serve as the neutral and bonded neutral to ground in subpanel. Not good.

Having your ground and neutral bonded in the subpanel makes it so you can get fried under certain circumstances. I think one of the real electricians who comes on this site posted a nice diagram in another thread.

Your system right now will make things run so everything gives the illusion of being ok. But under certain conditions death can result.

It appears that things could be corrected by running a 4 wire to the subpanel and separating the neutrals and grounds. But with the fundamentals being wrong you better check out everything very carefully.

jogr 11-06-2007 02:24 PM

Nate types faster than me and brings up an interesting point. Perhaps if there is no other connection between the building the risk is mitigated???

NateHanson 11-06-2007 02:40 PM

Quote:

Originally Posted by jogr (Post 72020)
Nate types faster than me and brings up an interesting point. Perhaps if there is no other connection between the building the risk is mitigated???

I'm pretty sure that his setup not only "mitigates the risk", but is actually completely code compliant (at least in ME, USA). I just installed a 3-wire feeder for a subpanel in a detached shop. I pulled a permit and it passed inspection. Sounds just like the one the poster describes.

Andy in ATL 11-06-2007 03:02 PM

It's compliant, but not for long. I would add the fourth wire if I was repulling this, keeping all the neutrals and grounds seperate. Google objectionable current.

Edit to add....I've never been to Canada!!! Don't know the rules up there!!!

slakker 11-06-2007 08:27 PM

Thanks for all the feedback, I'll double check the codes for up here and see what it says... I don't have a full code book, but one of those abridged versions for homeowners, so we'll see what I can find...

BTW> There are no other metallic runs to the shed... just the overhead feeder...

Andy in ATL 11-06-2007 08:33 PM

I guess the moral of the story is.... no matter if you are in
Can, the US , or frikkin Honduras... It is MUCH BETTER AND SAFER to keep the grounds and neutrals seperate except where they are bonded together at the service entrance to your house.

goose134 11-07-2007 12:10 AM

Andy, I agree with you 100%. The neutral should only be bonded at the point of service. I said it was OK because of the installation being overhead. If there is a raceway installed you should never bond the neutral again. This was one of the reasons I had asked him to meter his ground. My concern was the ground was functioning as a return to the main load center. I would recommend piping it over to the shed and remove the bonds.

slakker 11-07-2007 11:09 AM

Quote:

Originally Posted by goose134 (Post 72170)
I would recommend piping it over to the shed and remove the bonds.

I'm not sure I understand... can you elaborate? Don't want to screw it up when I redo this...


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