The Electrical Contractor Network

ECN Electrical Forum
Discussion Forums for Electricians, Inspectors and Related Professionals

Books, Tools and Test Equipment for Electrical and Construction Trades

Register Now!

Register Now!

We want your input!


2017 NEC and Related
2017 NEC
Now Available!

Recent Posts
Parking lot pole light swap....
by gfretwell
10/22/16 09:52 PM
International Wire Colour Codes
by Texas_Ranger
10/22/16 08:24 AM
Son of Sparky
by HotLine1
10/20/16 07:43 PM
Speaking of Plugmold ...
by gfretwell
10/17/16 02:37 PM
Broken battery charger? Check for cobwebs!
by gfretwell
10/17/16 02:30 PM
New in the Gallery:
12.5A through 0.75mm˛ flex (just out of curiosity)
Shout Box

Top Posters (30 Days)
gfretwell 12
renosteinke 6
HotLine1 6
ghost307 5
Potseal 4
Who's Online
2 registered (gfretwell, mbhydro), 251 Guests and 4 Spiders online.
Key: Admin, Global Mod, Mod
Topic Options
Rate This Topic
#11457 - 07/12/02 10:29 PM transformer grounding
Eandrew Offline

Registered: 05/24/02
Posts: 69
Loc: seattle, wa, usa
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.

Work Gear for Electricians and the Trades

Work Gear for Electricians and the Trades
Work Gear for Electricians and the Trades
Arc Flash Clothing, Gloves, KneePads, Tool Belts, Pouches, Tool Carriers, etc. etc....

#11458 - 07/13/02 04:14 PM Re: transformer grounding
electric-ed Offline

Registered: 07/08/02
Posts: 184
Loc: Canada
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.


#11459 - 07/14/02 11:35 AM Re: transformer grounding
Eandrew Offline

Registered: 05/24/02
Posts: 69
Loc: seattle, wa, usa
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 07:44 AM Re: transformer grounding
The Watt Doctor Offline

Registered: 12/23/01
Posts: 443
Loc: Mont Belvieu, TX
Ed is correct. I would just add on thing. Have a look at 250.30 (A)(1) in the 2002 code. It states that " 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,
The Watt Doctor
Altura Cogen
Channelview, TX


ECN Electrical Forums - sponsored by Electrical Contractor Network - Electrical and Code Related Discussion for Electrical Contractors, Electricians, Inspectors, Instructors, Engineers and other related Professionals