ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Shout Box
Recent Posts
Changing a Bulb
by gfretwell. 07/14/18 03:12 PM
Tray cable?
by gfretwell. 07/11/18 10:18 PM
Eaton Heavy Duty 30A and 60A Safety Switches
by Admin. 07/11/18 09:49 PM
ORTOVOX Recalls Avalanche Transceivers
by Admin. 07/11/18 09:44 PM
Tingle off the water spigot
by gfretwell. 07/08/18 12:58 PM
New in the Gallery:
Plug terminals
Housebilding DIY wiring
Who's Online Now
0 registered members (), 17 guests, and 9 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Ugh, more sub panel questions. #177081
04/21/08 08:03 PM
04/21/08 08:03 PM
E
EV607797  Offline OP
Member
Joined: Oct 2006
Posts: 745
Fredericksburg, VA, USA
I have two scenarios involving sub panels and my son (who is doing the work) and I are at odds, so please tell me what you think:

Scenario #1 (his project):

Commercial work; 200 amp, 120/208Y service and the panel is full. We need to place a 100 amp sub panel to add a couple of circuits. In order to do this, I plan to take three existing 20 amp single pole breakers and move them into the sub panel to make room for the 3-pole 100 amp breaker to feed the sub panel. My son wants to leave the three S/P circuit's neutral on the neutral bar in the main panel. I told him no, that all conductors associated with a multiwire circuit must stay together. This meaning that he needs to bring the neutral over to the neutral bar in the sub panel. Am I right here?

Scenario #2 (my project):

Residential work, 200 amp single-phase service, panel is full. I hate using skinnies or piggyback breakers to make space, even though they are legal in this panel. I want to use a sub-panel to accommodate a hot tub circuit. My plan is to pull the 2P30A breaker out for the air conditioning to make room and replace it with a 2P100A breaker to feed the sub panel (yes, the existing GE panel is rated for 100 amp breakers when using type THQL). The sub panel will be mounted directly below the main panel and just be connected with a PVC nipple. I plan to extend the existing #8AL conductors for the air conditioning unit through the nipple into the sub panel, but leave the ground connected to the neutral bar in the main panel. All four conductors for the hot tub circuit will originate from the sub panel which will have the EGC and neutral isolated.

Since the EGC isn't a current carrying conductor associated with the air conditioning circuit, is it OK to leave it alone and just bring the current-carrying conductors into the sub panel through the nipple by themselves?

As you can see, my son and I are butting heads here because he's still having trouble comprehending the EGC/neutral issue with sub panels. Now that he's pushing me, I guess I am starting to question myself at this point. I feel that an EGC can connect to either panel, but the neutral(s) associated with a circuit must originate from the same panel. Any suggestions that you may have for both scenarios will be greatly appreciated. I hope that I win this debate.


---Ed---

"But the guy at Home Depot said it would work."
2017 / 2014 NEC & Related Books and Study Guides
Re: Ugh, more sub panel questions. [Re: EV607797] #177086
04/21/08 09:26 PM
04/21/08 09:26 PM
renosteinke  Offline
Cat Servant
Member
Joined: Jan 2005
Posts: 5,316
Blue Collar Country
Forgetting the fine print of the code, it's good practice to have all the wires that have anything to do with a circuit wind up in the same panel. It's also nice that nothing go through the feeder conduit but the ... feeders laugh

Keep in mind, regardless of the distance between the panels, or the method of connection ... always run the necessary four wires. Depending on a nipple, a screw, or any other hardware for uniting the grounds is unreliable - and if you try that with the neutral (heaven forbid!), you're setting things up for a major failure down the line. (Visit the chat room if you want to hear how I spent my Thanksgiving!)

Re: Ugh, more sub panel questions. [Re: renosteinke] #177091
04/21/08 10:30 PM
04/21/08 10:30 PM
E
EV607797  Offline OP
Member
Joined: Oct 2006
Posts: 745
Fredericksburg, VA, USA
Oh, I would never even dream of installing a sub panel without all conductors. I've seen enough sub panels with no neutral to make my head spin. $5.00 worth of wire makes it hardly worth cutting that corner and that's with today's copper prices.

I also agree that it's tacky to have anything but feeders in the nipple (that didn't sound good). I plan on butting the sub panels below the existing panels on both jobs with dual 1.5" nipples. Ouch, that sounds even worse, but you know what I mean from a professional standpoint, right?


---Ed---

"But the guy at Home Depot said it would work."
Re: Ugh, more sub panel questions. [Re: EV607797] #177097
04/21/08 11:09 PM
04/21/08 11:09 PM
G
gfretwell  Offline

Member
Joined: Jul 2004
Posts: 9,242
Estero,Fl,usa
Back when there were computer rooms we always spec'ed the computer room panels to NOT have a neutral brought to them. We landed the EGC on the grounding bus and used the neutral bus for the IG that went to the machines. That insulated IG conductor went straight to the ground bus in the service disconnect unattached.
All real mainframe equipment was 208 or 240, no 120.


Greg Fretwell
Re: Ugh, more sub panel questions. [Re: gfretwell] #177222
04/25/08 02:37 PM
04/25/08 02:37 PM
E
EV607797  Offline OP
Member
Joined: Oct 2006
Posts: 745
Fredericksburg, VA, USA
I'm bumping this post up because I have a $100.00 bet riding with my son that he's wrong.


---Ed---

"But the guy at Home Depot said it would work."
Re: Ugh, more sub panel questions. [Re: EV607797] #177223
04/25/08 02:48 PM
04/25/08 02:48 PM
G
gfretwell  Offline

Member
Joined: Jul 2004
Posts: 9,242
Estero,Fl,usa
I think it will be a tough bet to collect. What he is doing may be a questionable design but I am not sure it is a violation.


Greg Fretwell
Re: Ugh, more sub panel questions. [Re: gfretwell] #177226
04/25/08 03:37 PM
04/25/08 03:37 PM
B
BryanInBalt  Offline
Member
Joined: May 2007
Posts: 47
Baltimore
A suggestion I'd makre wrt to the resi sub panel job is to think about the next project (the genset/ats) and isolate the circuits most likely to be fed by the undersized genset the customer will want to install. wink

As to the comm'l job, all branch circuit wires associated should be only in the panel they originate from.


Design-Build isn't supposed to mean design *as* you build.

Featured:

2017 Master Electrician Exam Preparation Combos
2017 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Member Spotlight
RonKipperDatacom
RonKipperDatacom
Kansas City, KS
Posts: 30
Joined: January 2013
Show All Member Profiles 
Top Posters(30 Days)
Admin 5
Popular Topics(Views)
248,139 Are you busy
185,594 Re: Forum
174,938 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.6.1
(Release build 20180101)
Page Time: 0.020s Queries: 15 (0.005s) Memory: 0.9891 MB (Peak: 1.1456 MB) Zlib enabled. Server Time: 2018-07-20 08:49:15 UTC