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
Yesterday at 08:46 PM
International Wire Colour Codes
by Tjia1981
10/23/16 12:08 PM
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 14
HotLine1 7
ghost307 7
renosteinke 6
Potseal 4
Who's Online
0 registered (), 298 Guests and 4 Spiders online.
Key: Admin, Global Mod, Mod
Topic Options
Rate This Topic
#129416 - 02/26/05 06:37 PM lost neutral
ds247 Offline

Registered: 05/17/03
Posts: 18
Loc: California
I was working on a furnace which uses 120v and the control circuit uses 24v. I checked the two secondary leads on the transformer and got 0v. Then I checked the primary hot lead and the chassis and got 120v. Turns out the primary neutral had a bad connection. My question is when I checked either secondary lead (without the primary neutral connected) to the chassis i got 12v. How could I get anything when there is no current flow through the primary side of the transformer? Thanks

#129417 - 02/26/05 08:51 PM Re: lost neutral
Trumpy Offline


Registered: 07/05/02
Posts: 8532
Loc: SI,New Zealand
By rights, you shouldn't have had 12V to the Chassis (unless one side of the Secondary is connected to it).
Assuming that this is a Double-wound transformer, there should only be voltage between the two secondary leads.
It sounds like there is a broken turn on the Secondary side of the transformer.
Let's face it, these days if you're not young, you're old - Red Green grin

#129418 - 02/27/05 02:46 AM Re: lost neutral
pdh Offline

Registered: 01/20/05
Posts: 354
This could be capacitive coupling across the transformer and returning over the chassis to the 120v ground. Or if the neutral is broken in a way that allows it to capacitively couple with a ground wire, it could be a complete circuit through that coupling. Put a 24v load on the secondary (a pigtail socket with a 100w 120v light might do). If the former cause, the 12v may remain. If the latter cause, it should go away.


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