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Upgrading old sub panel #204122 11/14/11 04:31 PM
Joined: Nov 2011
Posts: 1
M
Matto1225 Offline OP
New Member
Hello, just wanted to say first of all I did search for an answer on this but its hard for me to get a straight answer out of some of the threads.

So here it is. I have an attached garage on my house with a pretty old sub panel(screw in fuses) that is fed by a 6/3 wire to give me 2 hots and the neutral. No ground.

I want to upgrade this to a breaker type sub panel with a few extra spaces so I can do a few more things in the garage. I would like to avoid running an entire new 4 wire feed to the sub panel and reuse as much as I can as the house panel and sub panel are very far apart.

I do have my well point about 10' from the sub panel in the garage as well.

So here is the list of questions:

1.) Can I use the 6/3 wire currently feeding the fuse box?

2.) If adding a ground is needed can I run a ground wire to the well point from the sub panel? Just FYI the MAIN house panel is grounded to the well point already as well as two ground rods.

3.) How would I configure the sub panel as far as bonding or not, adding a seperate ground bar in it or connecting ground and neutral wires to same bar.

Any help is appreciated. thank you much!

Matt

Work Gear for Electricians and the Trades
Re: Upgrading old sub panel [Re: Matto1225] #204123 11/14/11 05:37 PM
Joined: Dec 2000
Posts: 4,286
electure Offline
Member
Matto
Q1.) No. You'll need a ground at the sub. You'll have to run a 4 wire feeder from the main panel.

Q2.) No. You'll need to run a 4 wire feeder from the main panel. The equipment ground needs to be in the same cable as the feeder.

Q3.) You'll need both an insulated neutral bar and a ground bar, with the respective conductors connected to each

Re: Upgrading old sub panel [Re: Matto1225] #204124 11/14/11 05:39 PM
Joined: Apr 2002
Posts: 7,220
HotLine1 Offline
Member
Matt:

Welcome to ECN Forums!

Your profile indicates that you are a 'general contractor', not an electrical contractor/electrician. Is that correct??



John
Re: Upgrading old sub panel [Re: electure] #204125 11/14/11 06:36 PM
Joined: Dec 2001
Posts: 2,486
T
Texas_Ranger Offline
Member
Quote
Q2.) No. You'll need to run a 4 wire feeder from the main panel. The equipment ground needs to be in the same cable as the feeder.

Does it? I was under the impression that EGC are exempt from the "all conductors must be in one cable" rule.

Re: Upgrading old sub panel [Re: Matto1225] #204126 11/14/11 09:08 PM
Joined: Jun 2004
Posts: 1,273
T
Tesla Offline
Member
Texas...

You're correct... but it's still going to have to bond back with the Service if this daughter panel is to operate correctly.

It would also appear that a fresh GEC needs to be installed at the outbuilding...

If the outbuilding has Zero conducting paths back to the Service bonding would appear optional.

In which case one might think that the feeder could be treated as if it were a SDS.

If the feeder uses an overhead run then I'd expect bonding to be required.


Tesla
Re: Upgrading old sub panel [Re: Matto1225] #204128 11/14/11 10:20 PM
Joined: Dec 2000
Posts: 4,286
electure Offline
Member
Tesla:
The OP said this is an attached garage, not an outbuilding

Re: Upgrading old sub panel [Re: Matto1225] #204132 11/15/11 12:35 AM
Joined: Jul 2004
Posts: 9,547
G
gfretwell Offline
Member
I believe the only legal answer is to rerun the cable in 4 wire.


Greg Fretwell
Re: Upgrading old sub panel [Re: Tesla] #204133 11/15/11 10:28 AM
Joined: Dec 2001
Posts: 2,486
T
Texas_Ranger Offline
Member
Originally Posted by Tesla
Texas...

You're correct... but it's still going to have to bond back with the Service if this daughter panel is to operate correctly.

Of course, but a 3-wire cable plus separate grounding conductor to the main panel would achieve that just as well as a 4-wire cable. Or am I missing something?

Re: Upgrading old sub panel [Re: Matto1225] #204134 11/15/11 11:05 AM
Joined: Jan 2005
Posts: 5,316
renosteinke Offline
Cat Servant
Member
Yes, Texas, you missed something.

The OP needs to run a ground wire between the panels. This wire would be a "EGC," or EQUIPMENT grounding conductor.

The OP suggests that he instead run a separate wire to his well. This would be a "GEC," or grounding ELECTRODE conductor. Different wire, different purpose.

The OP's idea fails, as 'grounding' the panel to the well will do nothing to help fault current return to the PoCo transformer. He is confusing the electrical 'ground' with the earth under his feet.

A word to the OP: There are sizing issues here as well. You probably ought to have a chat with an electrician. We're out of DIY territory.

Re: Upgrading old sub panel [Re: Matto1225] #204135 11/15/11 01:41 PM
Joined: Jul 2004
Posts: 9,547
G
gfretwell Offline
Member
The problem I see is the neutral. A 2 wire with ground cable usually has an uninsulated EGC that can't be used as the neutral (plus it will usually be smaller than the ungrounded conductors) and there is no provision to run a neutral outside of the cable or raceway.
If, by some strange reason, they did run a 3 wire (red, black white) cable with all conductors insulated he might be able to establish his EGC with a separate wire.

As for just grabbing the grounding electrode conductor at the well point, You might be able to make a case for it.

Quote
250.130 Equipment Grounding Conductor Connections.
Equipment grounding conductor connections at the source of separately derived systems shall be made in accordance with 250.30(A)(1). Equipment grounding conductor connections at service equipment shall be made as indicated in 250.130(A) or (B).

(A) For Grounded Systems. The connection shall be made by bonding the equipment grounding conductor to the grounded service conductor and the grounding electrode conductor.




Greg Fretwell
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