ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat
Recent Posts
Do we need grounding?
by gfretwell - 04/06/24 08:32 PM
UL 508A SPACING
by tortuga - 03/30/24 07:39 PM
Increasing demand factors in residential
by tortuga - 03/28/24 05:57 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 (), 376 guests, and 7 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
#11457 07/13/02 01:29 AM
Joined: May 2002
Posts: 68
E
Eandrew Offline OP
Member
when is transformer grounded like a service? I mean, when would you have a double barrel lug on xo with both a ground and nuetral terminated on it.

Transformers in electrical rooms I've worked on (eg:90kva) 480/277 stepdown to 208/120 did not have the ground tie in with the neutral. However, I've seen temp skids and certain roof top transformers with had the ground go through a grounding bushing then to the frame of the trans. and then up to the neutral terminal (xo) along with the nuetral.

Is this done if lighting strike are a concern?like on a roof? or an outdoor temp skid. service ground VS equipment ground.

#11458 07/13/02 07:14 PM
Joined: Jul 2002
Posts: 175
E
Member
If the transformer is supplying a system that is required to be grounded (one that has a neutral conductor), the grounding electrode conductor (GEC) can be connected to the neutral either at the transformer XO terminal, or at the neutral buss of the first switch controlling the system.

Ed

#11459 07/14/02 02:35 PM
Joined: May 2002
Posts: 68
E
Eandrew Offline OP
Member
Thanks Ed.

So its an optional thing. I wonder if there is an advantage of grounding the neutral at the transformer versus the first disconnecting means.

#11460 07/15/02 10:44 AM
Joined: Dec 2001
Posts: 440
Likes: 3
Member
Ed is correct. I would just add on thing. Have a look at 250.30 (A)(1) in the 2002 code. It states that "...it shall be made at the source of a seperately derived system that has no disconnecting means or overcurrent devices." If you are feeding a panel that doesn't have a disconnecting means, you must leave the "strap" (bonding jumper) in it that comes from the factory, or put one in it if it doesn't have one. I've never seen a wye type transformer that didn't come with a factory bonding jumper. If your panel has a disconnecting means, and you want to bond the neutral at the panel, it is perfectly legal, but most installations that I've seen, and done, have the bond on the secondary side of the transformer. My reasoning, you may ask? I figured, why should I remove, and replace something that the "factory" has done for me. I couldn't tell you if there are any advantages or not. I will say this, "If you have a factory installed bonding jumper that aint broke, then don't fix it."

I've been truely transformed,
Doc


The Watt Doctor
Altura Cogen
Channelview, TX

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