OT- garage wiring question

I bought a Millermatic 175 this week and have been rewiring my garage to bring it up to code. My sub-panel did not have a ground bus but did have a ground line coming from the house. According to code, I need to isolate the ground and common. I took a reading from the common bus and the panel box and there was <no continuity>. I installed a ground bus (grounding the box), connected the ground from the house, connected all of the ground wires in the sub-panel, and then tied in a line running to a ground rod just outside the garage. After I hooked up all of the above, there <is continuity> between the common and box???? No wires are crossed or touching. Any advice is appreciated.

Thanks -JAM

 

Are you talking Continuity between the common hot bus or the common ground bus and the panel?

 

Did the snow rot your brain, or mine? Sorry man you lost me. Although if you can't figure it out give me a call 330-928-1707 and I can walk you through it. Jerry Upon rereading your post I think you mean nuetral bus instead of common bus. Alot of subpanels have a "common" or electrically connected nuetral / ground bar. If that helps.

 

First off I am NOT an Electrician - as a result I am NOT qualified to give Professional Advice. I would take the following comments simply as statements of what I personally believe to be true - as always the LOCAL ELECTRICAL CODE is the FINAL SAY.

Aside from local codes which vary - the general method for garage wiring might go something like this:

At your MAIN (house) you should have 2 "hots" (each measuring 120V to Nuetral or 240V across the two "hots") Next you should have a Ground and of course your Nuetral. Nuetral and ground will be tied together HERE (often you'll see where they tie your Neutral to your water pipe to get Earth Ground, but more recently they prefer a Ground Rod -probably due to all the plastic plumbing nowadays) Anyways you really shouldn't tie Nueatral to ground at multiple (additional) locations lest you risk Ground Loops which pose dangers of there own. So now your garage sub panel should have 4 wires from your house feeding it. 2 hots, 1 nuetral and 1 DEDICATED ground. I suppose the question arises when you have a Earth Ground (ground rod) at the Main and the Sub Panel - local code will be the final word here - I suspect some Codes require that while other do not.

With that said, your sub panel MIGHT show continuity from the box to neutral because ultimately they ARE connected at the MAIN. I assume you installed the "grounding screw" to the box from the ground bus - in this case the box is grounded and back at the main ground and nuetral are tied together so - it sounds "normal" to me.

I will look forward to hear what the Professionals say here.

 

Thanks Hemi-
The snow has rotted more than my brain. I think I may have figured it out- although reading about this stuff might as well be Chinese. I used the wrong terminology in my first note. Replace the word "common" with "neutral". Since the neutral is a grounded conductor and tied to a ground at the house (like you said), I would show continuity between the neutral <grounded conductor> and ground <grounding conductor> in my garage sub panel. In theory, if I remove the grounding conductor coming from the house, I will lose the continuity. I'll play with it tonight to see what happens.

Thanks -JAM

Oh- and in case you're wondering... I'm not an electrician ;-)

 

go back and read hemiramblers disclaimer and it applies to me too!

The neutral wire is at ground potential (zero volts), so you should expect there to be continuity between neutral and ground anywhere in the system, even if they're not connected together in that box.

Local codes vary, so whether or not to tie the neutral to ground at the garage panel is a question we can't answer!

 

I've done alittle of this type stuff in the house and garage and what I do is run all the wires but leave everything open, then hire an electrician to come in check it all out before he makes the final connections to make it "hot"...