ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat
Recent Posts
Square D "All-In-One" Panelboard
by NORCAL - 11/30/21 12:48 PM
Where is Everyone?
by luckyshadow - 11/21/21 10:14 AM
It's been an interesting career
by The Watt Doctor - 11/19/21 09:56 AM
Well I am back to stay (nearly 6 years)
by The Watt Doctor - 11/19/21 09:17 AM
Motor Load Relationships Between Fans and Pumps
by The Watt Doctor - 11/18/21 09:24 AM
New in the Gallery:
240/208 to a house
240/208 to a house
by wa2ise, October 9
Now you know.
Now you know.
by Tom_Horne, September 7
Who's Online Now
0 members (), 42 guests, and 21 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
#129416 02/26/05 09:37 PM
Joined: May 2003
Posts: 18
D
ds247 Offline OP
Member
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 11:51 PM
Joined: Jul 2002
Posts: 8,412
Likes: 3
Member
ds247,
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.

#129418 02/27/05 05:46 AM
Joined: Jan 2005
Posts: 354
P
pdh Offline
Member
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.


Link Copied to Clipboard
Featured:

Tools for Electricians
Tools for Electricians
 

* * * * * * *

2020 Master Electrician Exam Preparation Combos
2020 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Member Spotlight
Trumpy
Trumpy
SI,New Zealand
Posts: 8,412
Joined: July 2002
Top Posters(30 Days)
Admin 3
dsk 2
Popular Topics(Views)
286,328 Are you busy
218,794 Re: Forum
204,947 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.7.5