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
Page 2 of 2 1 2
#59098 11/28/05 05:13 PM
Joined: Dec 2004
Posts: 1,064
D
Member
Good catch Don....

Dnk..

#59099 11/28/05 05:30 PM
Joined: Sep 2005
Posts: 153
W
Member
@ Don:
In Europe an ungrounded system like this would mandatorily need a permanent isolation control, alalrming at the first fault and switching off at the second? (similar even for 24 VDC btw in Germany)

Same for you?

Wolfgang

#59100 11/28/05 09:08 PM
Joined: Mar 2005
Posts: 212
G
Member
Correct and correct. A bad case of headarectumitis here with no excuses. I hope deverson solved his problem.

#59101 11/28/05 09:27 PM
Joined: Mar 2005
Posts: 20
D
Member
I think my first option is to try a 100 amp CB. I looked into a 125 but was told Cutler Hammer didn't offer one, plus the 100 amp was available next day. Both of the transformers megged fine and approx the same. I'll keep updates current. No pun intended!!!
Dave

#59102 11/28/05 11:52 PM
Joined: Sep 2003
Posts: 650
W
Member
Wolfgang raises an important issue. The secondary of this transformer is a separately derived systems, and must _either_ be grounded or meet the requirements for ungrounded systems.

But gaaaaaa. I can't find the code reference that requires ground fault detection on the ungrounded secondary. Am I imagining that ground fault detection is required? The closest that I can find is 250.21(3), which applies to control circuits only. (2002 code)

An an additional issue, the 480V secondary on this system is a pure 480V, not 480Y/277. You must use 480V breakers, not 480Y/277 breakers.

-Jon

#59103 11/29/05 12:14 AM
Joined: Mar 2005
Posts: 20
D
Member
The 480 volt secondary will only feed a 5 ton Liebert air conditioning unit. I have the secondary fused at 20 amps, well under what the transformer is capable of handling. I didn't included much info as it wasn't an issue as I couldn't get the transformer working let alone the Liebert.
Thanks
Dave Everson

#59104 11/30/05 06:09 PM
Joined: Mar 2005
Posts: 20
D
Member
Installed a 3 pole 100 amp breaker today and everything worked like a champ. I did notice a slight dimming of the lights when it fired up. It was fine after a second and everybody was happy.
Thanks for the help
Dave

resqcapt19 #185344 03/11/09 06:46 PM
Joined: Mar 2003
Posts: 849
Y
Member
Telsa's right
37.5 x 1000 = 37500 divided by 359.84 (1.73 x 208)= 104.21 amps primary.
37.5 x 1000 = 37500 divided by 830.4 (1.73 x 480) = 45.18 amps secondary.

Yoopersup #185351 03/11/09 10:29 PM
Joined: Apr 2002
Posts: 7,381
Likes: 7
Member
Yoop:
Why did you revive this thread? Did I miss something?

No problem with it, just wondering. I see names that have not been around in a while!



John
Page 2 of 2 1 2

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