I am not an electrician but a serious do it yourselfer that is interested in all aspects of remodeling. I am curious about the article by Clifford Popejoy on installing sub panels. I have just such a problem with my workshop being a good distance from the main panel and will have many large power tools hooked up.
In Clifford’s article (FHB #154) he talks about no having the neutral grounded in the sub panel. The photo on page 100 shows the neutral “floating” and the ground panel bonded.
My question is that it seems to me, not being an electrician, that the panel bonded bus bar has no neutral return. My assumption is that the ground line itself acts as the neutral eliminating the need for a second ground. Am I confused or just uneducated?
Also instead of the ground running all the way back to the main panel, how about just running a short lead to another copper water pipe or additional grounding rod?
I will probably have an electrician install the panel but want to watch and make sure it is done right.
Bob
Replies
"My question is that it seems to me, not being an electrician, that the panel bonded bus bar has no neutral return. My assumption is that the ground line itself acts as the neutral eliminating the need for a second ground. Am I confused or just uneducated?"
I am not real sure of your question and I don't have the article handy. But on a sub-pannel you don't mix the grounds and the neutral.
All of the neutral wires from the loads connect to the neutral buss and then you have a neutral wire that goes back to the main pannel. Then neutral system is designed to carry current.
The ground system does not normally carry current, it is designed only for safety. There are several purpose for it. One is to make sure that all "metal" is at the same potential in a building. Thus the water pipes, furance ducting, etc are all bonded to ground. Because the neutral carries current it can not be used as the ground because you will have a voltage drop across it and if the connection back to the pannel is lost then those metalic surfaces can become hot.
"Also instead of the ground running all the way back to the main panel, how about just running a short lead to another copper water pipe or additional grounding rod?"
Many reason this is not done. In fact current code does not allow any grounding to the water pipe except where it enters the building and then it has to be supplimented with other grounding.
First you want all of the wires run together so that it is more likely that if one is damaged they all will be, or at least it will be known. If you run the ground seperately it can later be disconnected and no one knows unitl it is too late.
Plastic is now being used for a lot of piping and sometimes section of metal pipe get replaced with plastic.
And last, but not least, plumbers get real upset with then disconnect a section of piping and find that there is voltage across it.
Bill,
You beat me to it! Nice explanation.
We split that topic (ground vs neutral) out of the article and put in the "What's the Difference" department. It's tough to cover both the technique and the theory in a six-page article.
Cliff