Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Electrical

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread Display Modes
Old 05-25-2009, 12:56 AM   #1
Newbie
 
Join Date: May 2009
Posts: 18
Rewards Points: 10
Default

Generator SUB-SUB panel


My generator subpanel was installed with the help of an electrician years ago. He attached the both the white and green wires from the subpanel to the neutral bar in the load center. I remember asking him about this and him mentioning that neutral and ground both go to the same place anyway, and that it was only important that they be separate in the subpanel, which they are.

Well, I've learned more since then, and discovered that my load center has an isolated neutral bar, it is not tied to the ground bar. WHY? I wondered, then it dawned on me. There is no main breaker in my load center, the main breaker is actually beside the meter (50 feet away). Therefore, my load center is not the "main panel", it is technically a subpanel. Therefore my generator panel is a subpanel of a subpanel.

With this new knowledge, I assume it is not okay to connect the ground from the subpanel to the neutral bar in the load center, because doing so ties neutral/ground together, in a slightly indirect way. I have moved the green wire to the ground bar.

Does that sound like a correct fix? What bad things could have happened if I hadn't fixed this? With this configuration (Subpanel running off subpanel) what other issues/potential problems should I be aware of?


Last edited by Miranda7; 05-25-2009 at 02:29 AM.
Miranda7 is offline   Reply With Quote
Old 05-25-2009, 03:14 AM   #2
My License Ain't 4 Sale..
 
Join Date: Feb 2008
Location: Atlanta, Ga/Hamilton, Al
Posts: 1,813
Rewards Points: 1,000
Default

Generator SUB-SUB panel


Yes, you are correct. What bad things could have happened? The ground from the generator could have carried some neutral current, and depending on connections, possible energized the metallic frame of the sub panel or generator. Is that very likely? No, not really. In reality, it would have probably continued to operate fine for the rest of its life. But the chance still existed for parallel neutral paths.

How is the genny sub set up? Is it a transfer switch, or lockout or what? Just curious.

InPhase277 is offline   Reply With Quote
Old 05-25-2009, 07:03 AM   #3
Member
 
Join Date: Nov 2007
Location: Nashua, NH, USA
Posts: 6,968
Rewards Points: 2,032
Default

Generator SUB-SUB panel


Except for how the ground wire and neutral wires are connected to its "parent", there are no other issues specifically related to "sub-subpanel" versus "subpanel".
__________________
Forget super sized fries. The Washington Redskins could promote healthy eating with First Lady Obama by choosing a (red skinned) turnip for a mascot.
AllanJ is offline   Reply With Quote
Old 05-25-2009, 07:42 AM   #4
Member
 
Join Date: Sep 2008
Location: Oregon
Posts: 1,497
Rewards Points: 500
Default

Generator SUB-SUB panel


The reason you have a separate ground and neutral at subpanels is the same reason electrical outlets have a separate ground and neutral wire!

Let's take an outlet as an example. Say there was no separate ground wire, and that the ground was connected to neutral at the outlet.

Then let's say you have a microwave oven plugged into that outlet and the metal frame of that oven is connected to the ground prong of the outlet.

Then let's say a workman comes along and drills a hole into your wall to install something, and he accidentally drills through the neutral wire going to that outlet.

Now there is only a hot wire going to the microwave outlet...

You turn on the microwave and it does not work. Then you grab the metal cabinet of the microwave to move it to check the plug in the back and you get shocked! The hot connection is traveling through the "turned-on" microwave, then back out to the neutral connection, then to the ground connection at the outlet, then back up the ground wire to the metal cabinet! (Making the metal cabinet "hot".)

The same thing can happen with a subpanel basically. The only difference is the subpanel is further down the line. AND with something like this happening at a subpanel, EVERYTHING the subpanel feeds would have the problem of the metal cases being hot as opposed to the above example where just one outlet had the problem.

This separate ground/neutral wiring protects in certain "malfunction" situations, that being a broken (drilled through) wire. Or in the case of a "loose" connection. Actually these malfunction situations are not that rare.

As to the generator transfer switch, there are new OSHA rules that certain portable generators be equipped with a GFCI. In this case, a neutral connected to a ground can cause the generator GFCI to trip! (And this is a whole new set of problems!)
Billy_Bob is offline   Reply With Quote
Old 05-25-2009, 09:43 AM   #5
Newbie
 
Join Date: May 2009
Posts: 18
Rewards Points: 10
Default

Generator SUB-SUB panel


Wow, great information guys! Billy you have explained isolated ground better than anywhere I have seen it. You post should be a sticky!

The generator subpanel is a gentran, the type with the built in manual transfer switch/lockout. The generator is a portable generac, and the neutral/ground bonding strap has been removed from the generator. I also have a jumpered prong plug on hand to use to rebond the ground and neutral when the generator is used as standalone and not connected to the house. Sound right?

I have other questions relating to this generator panel under a thread "Arcfault grandfathered" and I would be VERY appreciative if you guys could take a look at that thread as well and give your opinions.

Last edited by Miranda7; 05-25-2009 at 09:49 AM.
Miranda7 is offline   Reply With Quote
Old 05-25-2009, 11:26 AM   #6
Member
 
Join Date: Jun 2007
Posts: 3,510
Rewards Points: 2,008
Default

Generator SUB-SUB panel


Quote:
Originally Posted by Billy_Bob View Post

Let's take an outlet as an example. Say there was no separate ground wire, and that the ground was connected to neutral at the outlet.
Then this is is non-compliant install from the start. Ground wires are and were never intended to carry current except fault current.

J. V. is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Old House Rewire finnimus Electrical 15 05-13-2011 11:39 PM
Adding a second Electric sub panel TW Lucas Electrical 9 10-05-2008 03:37 AM
Replacement Meter Panel leonard_voet Electrical 19 04-09-2008 11:27 AM
Installing new (service?) breaker panel and generator panel Nhrafan Electrical 6 04-01-2008 04:03 PM
turn main panel into a sub panel? tikicarver Electrical 2 01-24-2008 08:37 AM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.