Help with wireing

DTCOOPER · Feb 27, 2009

there are hundreds of thousands of subpanels done this way..
2005 code said you could bond the neutral to the can and drive the new ground rod, so long as you were not bonded some other way with the original structure, through water lines, phone lines, etc.. Basically treating it as a new service, with the incoming power from your house panel, acting just like the incoming feed from the utility if you will.

Code says that beyond service entrance (main panel) the neutral and ground are not to be bonded..
I have managed an electrical supply house for several years here in Texas. I can tell you that here in the "country" we still do it per 2005 code..
No reason to waste the wire necessary to run the 4th conductor to a subpanel 100+ feet away.. JMHO... So take my opinion, and the current code, and decide which way you wanna do it.. Glad to help.

2manyrocks · Feb 27, 2009

Thank you, sir.

buckeyefarmer · Feb 28, 2009

WVBill said:
If you are going to have to get this inspected by your jurisdiction's building or electrical inspector, the only sure way to have it pass is to ask the inspector in advance.

When I ran the electrical out to my wife's studio building, I studiously researched the subject of grounding, grounded, bonding, neutral etc. etc. in books and multiple internet sources all of which said NOT to bond (connect) the neutral (white wire) bus and the grounding (bare wire) bus in the panel out in the studio building. So I didn't. But I kept the screw that goes in the panel to make the bond sitting on the window sill next to the box in the studio.

When the inspector came he looked in the box and said "good work". Then he picked up the screw and said "if you'll put this in you'll pass". So I did.

WVBill

If you ran the circuit from the main panel to the sub panel as 2 hots, neutral, and ground, then bonding the neutral and ground at the sub panel I believe violates the code as this creates two bonding locations.

buckeyefarmer · Feb 28, 2009

DTCOOPER said:
With the new codes that were changed between the 2005 and 2008 codes, this has gotten lots of people in trouble. Especially if your municipality has in fact adopted the 2008 Code. As of 2005 code, you could have just run the 3 wires (2 hots and a neutral) to a subpanel (in a DETACHED STRUCTURE), so long as it's not bonded in any form or fashion (metal conduit, telephone line, etc) to the main panel. Then you would treat the new panel as a completely new service, with a grounding electrode driven at the new location.. Well that's all changed now !!

I'll touch on the important points between '05 code and '08 code:

#2 aluminum used to be allowed for 100A subpanels under an interpreted wording of a code article. They have now explicitly changed the wording so that #2 aluminum is good for 90A to a subpanel.

Three-wire feeds (no ground) used to be allowed to an outbuilding provided that no other metal pathways like a water line or phone line were present. Now, four-wire feeds are mandatory, no exceptions.

The ground rods are required in either case, and they should be connected to the subpanel ground bar with #6 copper wire.

If you don't have to worry about inspections, code compliance, etc: When a three-wire feed is used, the neutral and ground bar must be bonded; when a four-wire feed is used, the neutral and ground bars must not be bonded. In this instance, you are treating the subpanel as just another circuit..

The purpose of the neutral is to carry unbalanced load.. That's why you can run a 240v compressor with no neutral.. Just two hots and a ground. But when you add 120v load to the equation, you are sure to have unbalanced load, therefore you must have a neutral to carry that unbalanced load back to the main panel and then to ground.

What we have to remember is that the code is written as an idiot-proof set of instructions.. I could tell you shortcuts all day long that are perfectly safe... Just not legal. LOL