Please explain this old wiring.

Reply

  #1  
Old 05-18-08, 06:03 PM
New Member
Thread Starter
Join Date: Aug 2006
Location: New Jersey
Posts: 311
Received 0 Votes on 0 Posts
Please explain this old wiring.

I replaced a few lights in my Sisters house, I found odd situations with the wiring.

When the switch is turned off both wires read 120V to ground but nothing across them. When the switch is turned on only one wire reads 120V to ground, the other one is dead, it now reads 120V across them.

This was confirmed with my Klein Wiggy, my Fluke DMM, and my Fluke hot stick.

It's an old house with old wiring, altho the 100A panel is relatively new.

The old lights all worked with this wiring so I hooked up the new lights and they also work.

So what's going on here?
 
Sponsored Links
  #2  
Old 05-18-08, 06:15 PM
Member
Join Date: Sep 2000
Location: United States
Posts: 18,497
Received 0 Votes on 0 Posts
Could be an illegal California 3-way. In this very dangerous configuration, they sent the load two hot wires as an alternative way of turning it off.

Either that or it's phantom voltage, but your wiggy should not be fooled by that.
 
  #3  
Old 05-18-08, 06:18 PM
New Member
Thread Starter
Join Date: Aug 2006
Location: New Jersey
Posts: 311
Received 0 Votes on 0 Posts
Thanks for the reply. Only one of the lights was a 3 way, the others were normal. Is there something they could have done to make the normal switches work like that?
 
  #4  
Old 05-18-08, 06:26 PM
Member
Join Date: Sep 2000
Location: United States
Posts: 18,497
Received 0 Votes on 0 Posts
Yes, a California 3-way makes ordinary switches (i.e., not 3-way switches) work like 3-way switches.
 
  #5  
Old 05-18-08, 06:30 PM
New Member
Thread Starter
Join Date: Aug 2006
Location: New Jersey
Posts: 311
Received 0 Votes on 0 Posts
I'll look into that, thanks!
 
  #6  
Old 05-18-08, 09:19 PM
Tolyn Ironhand's Avatar
Group Moderator
Join Date: Nov 2007
Location: Twin Cities, MN
Posts: 13,016
Received 67 Votes on 59 Posts
I have run across in some older homes where they switch the neutral. That may be something to watch for.
 
  #7  
Old 05-18-08, 09:38 PM
New Member
Thread Starter
Join Date: Aug 2006
Location: New Jersey
Posts: 311
Received 0 Votes on 0 Posts
Originally Posted by Tolyn Ironhand View Post
I have run across in some older homes where they switch the neutral. That may be something to watch for.
The possibility of the installer switching neutrals is the only reason I even tested it with my hot stick (good thing I did, or else I could have had a bad day).

However, a switched neutral wouldn't produce the double hot effect I am getting at her house.
 
  #8  
Old 05-19-08, 07:58 AM
Member
Join Date: Sep 2002
Location: welland ontario
Posts: 7,012
Received 110 Votes on 100 Posts
Originally Posted by John Nelson View Post
Yes, a California 3-way makes ordinary switches (i.e., not 3-way switches) work like 3-way switches.
I'd like to see a drawing for that. All the California three way drawings I have seen still use three way switches.
 
  #9  
Old 05-19-08, 08:10 AM
Member
Join Date: Sep 2000
Location: United States
Posts: 18,497
Received 0 Votes on 0 Posts
Oh, you're right. I guess it would typically use 3-way switches. Each switch sends either hot or neutral to the light. If they both send the same thing, the light is off. If they send different things, the light is on.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: