New light fixture with 3 wires to replace old fixture with 2 wires


  #1  
Old 03-23-13, 06:45 PM
D
Member
Thread Starter
Join Date: Jan 2013
Location: Canada
Posts: 8
Upvotes: 0
Received 0 Upvotes on 0 Posts
New light fixture with 3 wires to replace old fixture with 2 wires

Hi. I'm trying to replace an old ceiling-mounted light fixture in my 1985 house for the first time.

When I unscrew the old fixture from the electrical box, I see that the old fixture has only 2 wires: a black and a white.

The old outlet box has two sets of wires coming out (as the light is controlled by two switches at either end of the room): both sets have white, red, black and bare copper wires coming out, with each set's copper wire being tied to a separate screw inside the metal electrical box, each set's red wire is tied to each other via a wire nut, each set's black wire is also tied to each other with a wire nut, and one set's white wire (which my voltage meter says is hot) is tied to the white wire from the old light fixture, and the other set's white wire is tied to the black wire from the old light fixture.

My question comes from that the new light fixture (one of those Leding track light fixtures from Ikea) has not only a black and white wire, but also a green/yellow wire (which I take to be the ground). The mounting bracket that came with the new fixture that is to be screwed onto the old electrical box also has a green wire attached to it that the Ikea instructions (a few pictures only, no verbiage) seem to indicate should be connected to both the green/yellow ground wire on the new fixture itself and the ground wire coming from the old fixture box.

However, both of the copper wires coming from each of the old sets of wires in the existing box are screwed down to the metal box itself (rather than being available to tie into the new fixture's ground wires). So, while I assume that the new fixture's white wire is to be tied to the same white wire in the box that the old fixture's white wire was tied to, and the new fixture's black wire is to be tied to the same white wire in the box that the old fixture's black wire was tied to, I'm not sure what to do with the new fixture's green/yellow ground wire (or the mounting bracket's green ground wire).

Do I unscrew one of the ground wires in the box from the screw it's screwed to the box with and tie it together with both the green wire from the new mounting bracket and the green/yellow wire from the new fixture? If so, how do I know which one of the copper wires in the electrical box to use? If not, what do I do with the two ground wires from the new fixture?

I'm new to this so any help you can suggest would be greatly appreciated. If there's something above that doesn't make sense or you need additional info, please let me know.

Thanks very much.
 
  #2  
Old 03-23-13, 07:07 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Jersey
Posts: 65,993
Received 4,154 Upvotes on 3,730 Posts
Nope.....make perfect sense. The ground wires are probably short and will now be difficult to work with.
If you had a crimp-on terminal you could crimp your two ground wires in a crimp terminal and then put it under the same screw the grounds are already under.

If there was enough ground wire......you could remove them both from the ground screw, twist them together with the two new ground wires and add an additional wire to go back to the box screw.

Make sense ?
 
  #3  
Old 03-24-13, 01:04 PM
D
Member
Thread Starter
Join Date: Jan 2013
Location: Canada
Posts: 8
Upvotes: 0
Received 0 Upvotes on 0 Posts
You bet. Just to confirm, because there's two light switches and wiring sets into the box, I have 2 existing bare ground wires in the box going to 2 screws into the box, so does it matter which one of those box screws I tie both of the two new wires from the new fixture and mounting bracket into? The Ikea instructions seem to indicate that both new wires should tie together and then tie into just one existing grounding wire/screw, but does it matter which screw? I wouldn't think so since they're both for grounding the two sets of existing wires.
 
  #4  
Old 03-24-13, 01:22 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Jersey
Posts: 65,993
Received 4,154 Upvotes on 3,730 Posts
Technically.....both of those bare grounds should go to one screw. Years ago they put each one on it's own screw. It's important that both of those wires connect back to the screws.... since you don't know which one is the actual source ground wire.

So....if you were to remove one ground wire from it's box screw...... make up a new splice with that wire, the two lamp grounds and a new tail connected back to that screw. That would maintain the original grounding method.
 
  #5  
Old 03-29-13, 11:25 AM
D
Member
Thread Starter
Join Date: Jan 2013
Location: Canada
Posts: 8
Upvotes: 0
Received 0 Upvotes on 0 Posts
OK, that seems to have worked with no issues at all. Thanks very much for your help.
 
 

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