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
2 members (ampherder, Scott35), 261 guests, and 17 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Page 1 of 2 1 2
#56043 09/13/05 07:44 AM
Joined: Jul 2001
Posts: 311
F
Member
In several of our local government buildings we have a 230V, 3Ph, 3W. electrical service. Measuring voltage to ground; A-G=230 volts, B-G=230 volts, C-G=0 volts. Why isn't there any voltage to ground on one phase?

[This message has been edited by Frank Cinker (edited 09-13-2005).]

#56044 09/13/05 07:47 AM
Joined: Sep 2003
Posts: 650
W
Member
Phase C is grounded. If this is supposed to be an ungrounded service, then there is a fault somewhere. But this is very likely 'corner grounded' delta rather than 'ungrounded' delta.

-Jon

#56045 09/13/05 08:53 AM
Joined: Aug 2004
Posts: 42
H
Member
Ungrounded systems are common in powerplants or substations. That way, IF one phase does become grounded, life goes on. Control of operations isn't effected.
Now a ground on a 2nd phase is another thing.

But I agree with Winnie. You most likely have a corner grounded system.If that is the case, your phase to ground reading is irrelevant.

HP

#56046 09/13/05 11:21 AM
Joined: Jul 2004
Posts: 9,923
Likes: 32
G
Member
That conductor should be white.


Greg Fretwell
#56047 09/13/05 10:51 PM
Joined: Feb 2005
Posts: 693
L
Member
You're so prejudiced!


Larry Fine
Fine Electric Co.
fineelectricco.com
#56048 09/13/05 11:36 PM
Joined: Jul 2004
Posts: 9,923
Likes: 32
G
Member
The jokes just write themselves from there don't they.


Greg Fretwell
#56049 09/15/05 12:14 AM
Joined: Oct 2001
Posts: 135
W
Member
I occasionally run into corner grounded delta in this area. It is rare and I have never gotten a good explanation for why that configuration appears in just one building in a neighborhood.
It seems to be old installations.

Anybody got a definitve answer?

#56050 09/15/05 01:07 AM
Joined: Jul 2004
Posts: 9,923
Likes: 32
G
Member
It is a very clean way to install 3p delta for motor loads if you don't need to serve 120v loads. You can use 2 pole equipment, one fewer service conductor and have 240v to run your motor on vs the 208 you get with wye.
Do you like "red leg" better? That comes with it's share of confusion too.


Greg Fretwell
#56051 09/15/05 09:08 AM
Joined: Oct 2001
Posts: 135
W
Member
240 with a high leg is very common in this area.

Two of the 240 corner grounded delta have been on an elementary school and a private school that was formerly an orphanage. Both had small a\c loads - split systems and small rooftops -no chillers. Both systems served lights and receptacles.
3 pole main disconnect with a solid plug in the grounded phase. 3 wires in and 3 wires out.

#56052 09/15/05 09:10 AM
Joined: Aug 2003
Posts: 1,374
R
Moderator
I think if this were an ungrounded system your measurement from phase "A" to ground and from phase "B" to ground would not be that close to each other. With an ungrounded system, the phase voltage to ground is erratic.


Ryan Jackson,
Salt Lake City
Page 1 of 2 1 2

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