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
1 members (Scott35), 260 guests, and 14 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
#128407 02/24/03 02:27 AM
Joined: Feb 2003
Posts: 8
A
Andre M Offline OP
Junior Member
Problem recently posted for my class:

Heating element rated 240v 4800W (20A) has been connected to 120/208v grounded "Y" system between two phases (208v). - Everybody egrees now 3600W / 17.3A.
1. Midpoint of the element is shorted to ground assuming 0 (zero) resistance of ground fault. What total power is rreleased during ground fault?
2. What current flow to ground?

What is your opinion on asked numbers? - Is it too hard for master electrician?

Andre

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
 

#128408 02/24/03 08:46 AM
Joined: Apr 2002
Posts: 197
G
Gwz Offline
Member
Find ohms of the original.

R = E / I, R = 240V / 20A, R = 12 ohms.

Now this is used on a 208/120V system.

The Neutral of 208/120V system is intentionaly connected to Ground and you noted 0 restistance to ground, thus the circuit at midpoint is being operated as on 120V system.

1/2 of the 12 ohms is 6 ohms.

I on the 120v as now operating is;

I = E / R, I = 120V / 6R, I = 20A on each of the two sections of the ground faulted 240, 4800W, 20A heater operated on the 208V system.

#128409 02/24/03 10:05 AM
Joined: Feb 2003
Posts: 8
A
Andre M Offline OP
Junior Member
Yes, thanks. Now a little harder second question. Find ground current.

#128410 05/25/03 06:48 AM
Joined: May 2003
Posts: 26
I
Member
20 Amps.

Ichabod

#128411 05/31/03 10:00 PM
Joined: Oct 2000
Posts: 2,723
Likes: 1
Broom Pusher and
Member
Should I draw this one up and post it in the Tech. Reference section?

Scott


Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!
#128412 06/01/03 09:36 AM
Joined: May 2003
Posts: 26
I
Member
Yes Scott, please do.

Ichabod


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