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Receptacle powered by switch, low voltage house electrical system

Receptacle powered by switch, low voltage house electrical system

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  #1  
Old 03-10-12, 02:15 PM
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Receptacle powered by switch, low voltage house electrical system

I have a house built in the 1950s and it has a low voltage electrical system. The way the system works is there are relays in the attic that the switches operate. The wire to the switches is only 22g. All the wiring to the load sources (receptacles and lights) is standard 12/14g. The wiring is only 2 conductor (white & black).

Most of the outlets are two prong (no ground). I have had success changing most out to 3 prong but in one room I am having a problem.

There are three receptacles all that have the top outlet controlled by a switch. the switch controls nothing else. If I change any of the receptacles out to a three prong style the switch no longer controls any of the outlets and all the receptacles are hot all the time.

The receptacle I just tried has only 3 wires coming into the junction box. 1 white and 2 black. In the old receptacle the white wire was connected to both silver screws and each black wire was connected to its own gold screw. I copied the set up exactly with the new style receptacle and light switch no longer works any outlets.

Any ideas what the issue is?

The old receptacle is a 15A 125V /10A 220V receptacle. I have no idea if this has anything to do with it.
 
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  #2  
Old 03-10-12, 02:42 PM
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Look between the old receptacles for a tab that is broken out. With the tab intact the receptacle will be hot all the time.
 
  #3  
Old 03-10-12, 03:39 PM
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I have had success changing most out to 3 prong but in one room I am having a problem.
I assume you are adding grounding conductors from the service panel to all receptacles as you change them to the grounding type.
 
  #4  
Old 03-10-12, 04:44 PM
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Good catch CJ, I read right past it.

To the OP, if there is no grounding means there are a limited number of methods to allow the change to three prong receptacles.
 
  #5  
Old 03-10-12, 04:54 PM
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Casual Joe,

No I haven't that would require ripping out walls. All the boxes are metal I have been running a ground wire to the metal boxes. I would imagine running back to the box and the houses ground is better but what is the danger of not doing that?
 
  #6  
Old 03-10-12, 05:03 PM
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PC,

Have to pull the receptacle back out but I wasn't breaking the tab off of the new one. So that might be the issue. Will check it out later and let you know. Thanks for the help.
 
  #7  
Old 03-10-12, 05:55 PM
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Without going back to the panel where the circuit originates or to the GEC, the ground you ran will just be floating. There will be no path back to trip the breaker.
 
  #8  
Old 03-10-12, 06:24 PM
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All the boxes are metal I have been running a ground wire to the metal boxes. I would imagine running back to the box and the houses ground is better but what is the danger of not doing that?
So, where is the ground wire you are installing originating. Even with a proper ground to the metal boxes, you still need to pigtail the ground to the devices.
 
  #9  
Old 03-11-12, 09:52 PM
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Breaking the tab was the issue.
 
  #10  
Old 03-11-12, 09:58 PM
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Thanks for letting us know. Glad you got it. Give us more detail on the grounding and perhaps we can help you make it safer.
 
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