ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat
Recent Posts
Increasing demand factors in residential
by gfretwell - 03/28/24 12:43 AM
Portable generator question
by Steve Miller - 03/19/24 08:50 PM
Do we need grounding?
by NORCAL - 03/19/24 05:11 PM
240V only in a home and NEC?
by dsk - 03/19/24 06:33 AM
Cordless Tools: The Obvious Question
by renosteinke - 03/14/24 08:05 PM
New in the Gallery:
This is a new one
This is a new one
by timmp, September 24
Few pics I found
Few pics I found
by timmp, August 15
Who's Online Now
0 members (), 255 guests, and 16 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
#98873 06/20/06 05:12 PM
Joined: Feb 2001
Posts: 308
S
Steve T Offline OP
Member
I had an engineer tell me today that a tankless hot water heater with sensitive electronic controls was not operating properly because a 'second ground' run thru a correctly installed emt was connected directly to the neutral bus in the service panel and not to a separate ground bus. He understands the two busses connect directly to one another in the panel, but he says it makes a difference and can create a ground loop which affects the point of reference of the electronic controls at the unit.

Could a foot and a half of #4 really make a difference? Maybe this should be in the technical area, but I was having trouble getting that one up.

Stay up to Code with the Latest NEC:


>> 2023 NEC & Related Reference & Exam Prep
2023 NEC & Related Reference & Study Guides

Pass Your Exam the FIRST TIME with the Latest NEC & Exam Prep

>> 2020 NEC & Related Reference & Study Guides
 

#98874 06/20/06 05:19 PM
Joined: Jul 2004
Posts: 9,923
Likes: 32
G
Member
Sounds pretty shaky to me


Greg Fretwell
#98875 06/20/06 05:35 PM
Joined: Jul 2004
Posts: 787
L
Member
Is there a significant amount of current running thru this 'second ground' wire? If so, is the temperature sensor wiring wrapped around this current carrying wire?

LarryC

#98876 06/20/06 06:30 PM
Joined: Feb 2005
Posts: 693
L
Member
Sounds like a shipment of male bovine excrement to me.


Larry Fine
Fine Electric Co.
fineelectricco.com
#98877 06/20/06 07:10 PM
Joined: Feb 2005
Posts: 693
L
Member
To add: I'd be willing to move the redundant ground to the other bus just to shut him up (meaning call his bluff).


Larry Fine
Fine Electric Co.
fineelectricco.com
#98878 06/20/06 08:58 PM
Joined: Jul 2004
Posts: 9,923
Likes: 32
G
Member
If there is a ground loop it is in his equipment not your wiring. There should be no way a "ground loop" in the line side of any equipment should affect the "data" side. He may have something grounded that shouldn't be but it is not in an article 300 wiring method. It is in his LAN or internal wiring.


Greg Fretwell
#98879 06/20/06 09:27 PM
Joined: Feb 2001
Posts: 308
S
Steve T Offline OP
Member
Thanks. I tend to agree with you guys, but this guy says their company does a lot of engineering for sensitive equipment--Honeywell and some others-- and says somethings dealing with inductance, capacitance (unspecific) he may not have known exactly, can cause this situation. When they removed the second ground all together, the unit works fine.

Like I said, I don't see how a short piece of wire can change all of this (especially when it is a #4 in a 200amp panel or a direct connection thru the panel enclosure itself) I guess I'd need to see the technical specs.

He said they were measuring a 1/2 amp on the ground wire. I don't know how they know there isn't current on the conduit.

Where's Scott? He usually has a complex answer.


Link Copied to Clipboard
Powered by UBB.threads™ PHP Forum Software 7.7.5