Old Bathroom Wiring?

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  #1  
Old 04-02-07, 07:22 PM
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Old Bathroom Wiring?

Hi all, ..Can someone make some sense of the way my bathroom wiring is run? The wiring is very old cloth type two wire cable with no ground. There is one switch box with two wires(black and white)(one cable) controlling a medicine cabinet light and a ceiling light. There are two single wires in both the medicine cabinet and ceiling box(one cable in each). With the power on there is power in both wires in each box (both med. Cab. and Ceiling light) all are hot)(only one wire is hot in the switch box). There is no neutral that I can find...The only way the cuircut is completed is by connecting the two wires in the switch box(or installing the switch). Can anyone explain how these wires are run? Is there any way I can install a double switch to control the lights seperately with this wiring set-up? Do I have to find a neutral from another source?
Thanks in advance...
 
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  #2  
Old 04-02-07, 07:34 PM
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knob and tube

This sounds like knob and tube wireing. The neutrals are most likely spliced in the wall. Very common for this wireing method (period).

Unfortunately, the best approach to meeting your desire.. is to rewire this room.
 
  #3  
Old 04-02-07, 07:39 PM
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There need not be a neutral at the switch box, but there must be a neutral at the light fixture.

You mention "cable", so that doesn't sound like K&T if you are using that word as we would use it.

When you say you are measuring "power", you are actually only measuring voltage. And without a ground, you have no good reference to measure the voltage against. So I'm not sure your testing is meaningful.

Clearly there is at least one box containing splices that are relevant to this puzzle. There is also one other thing clear: you cannot install anything else in the switch box without running more wires to it.

I recommend you don't do anything until your find all the boxes on this circuit and do enough testing to make a complete map of the circuit. I would really recommend that you not do anything even then, as it is not generally safe to modify wiring that is this old. In fact, it's not even legal.
 
  #4  
Old 04-02-07, 07:52 PM
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puzzled?

Hi..there is no neutral at either the medicine cab. or ceiling light box. I know this because my clip on light will not light when attached to these wires without the switch completing the cuircut(hough the wires show voltage with the senser). Im testing the wires with a voltage senser to see it they are hot. The wiring is not knob and tube but a very old cloth(covered) type romex cable. I cannot find any other junction boxes. The wiring works fine as is. I was just wondering how this may be wired because it doesn't make sense to me. I was thinking I could run a wire from the switch box to the medicine cabinet box and control it seperately... but I think I need a neutral...? It doesn't make sense to me that both wires in the Mad. Cab. and ceiling light box would show voltage?
Does that make sense? Thanks..
 
  #5  
Old 04-02-07, 08:09 PM
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Of course there is a neutral in each light. One of the wires is the neutral (should be the white one) and the other is the hot wire (should be the black one).

The two wires at the light switch are a switch loop.

Somewhere there is another junction. It should be in a box, but it's possible it's not and is buried in the wall, or it's possible that it is in a box and the box is buried.

Power goes to this junction. From here a switch loop goes to the switch. Switched power goes from here to the medicine cabinet light., Another cable brings switched power from the same box to the ceiling light.

You cannot add another switch and have one switch controlling each light without replacing the two wire cable that goes to the switch with a three wire cable.
 
  #6  
Old 04-02-07, 08:18 PM
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Puzzled?

If one wire is a neutral in each box why do both wires in each box show voltage with the voltage detector? I do have a 12/2 seperate romex cable running fron the switch box to the Med. Cab. Box. Is it possible to control it from a seperate switch? Thanks...
 
  #7  
Old 04-02-07, 08:19 PM
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Yes indeed, there is a neutral at each light. If the light ever comes on, there must be. It is impossible for them to work without one.
 
  #8  
Old 04-02-07, 08:21 PM
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You are not going to be able to control each light with a separate switch until you find the junction where the switch loop starts. Find that, and replace the switch loop wire with a section of 12-3 or 14-3 (depending on the circuit size).
 
  #9  
Old 04-02-07, 08:28 PM
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There are a hundred different ways to conduct tests that yield misleading results. Without being there to see what you're doing and how you're doing it and what test instrument you are using, it's hard to say why you are getting the results you are getting. It is theoretically possible for someone to describe their tests in enough detail for us to detect the problem in the forum, but, in my experience, very few people can do this well. I've given up even asking for this information since we almost never get what we want.
 
  #10  
Old 04-02-07, 08:30 PM
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Puzzled?

I undertand that there has to be a neutral in the Med. Cab. Box and Ceiling box for a light to light right? in either. So theoretically..if there is voltage in each box... and a supossed neutral..why wont the clip on light light up unless the wires in the switch box are connected? Both wires in each light box show voltage..
Puzzled?
 
  #11  
Old 04-02-07, 11:02 PM
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if this house is very old like from 30's or later generally will have old K&T {kont and tube } wireing and some how over the time someone did add the addital wires but a catch that there were quite few older home do have switched netrual so it can compound this matter.

as other suggest that if you are plan to do remodeling the bathroom it will be wise idea to run the new wires in there

what kind of clip on test light you have ?? some will be very senstive and some will be not sensitve at all ..

one trick i done this from time to time to find out if it was switched netural or not what i do is unscrew all the light bulbs and test with NCV [ nonconcat voltage tester] if it dont light up then you have netural at the fixure but if not then a good chance there is a hidden junction box or run of splice connection on older K&T wires that can be hidden in ceiling or wall [ some case you may tear open the wall to see it ]

but if the K&T wire is there the code do not allow to extend it at all leave that one alone and run new one from there

if more question please do post it here


Merci , Marc
 
  #12  
Old 04-03-07, 04:23 AM
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The switch turns on power to the lights. When the switch is OFF, there is no power to the lights.
 
  #13  
Old 04-03-07, 05:27 AM
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Puzzled?

Hi.. The tools I was using to test the wires was a Greenlee voltage sniffer..and a basic alligator clip on light socket with a 60 watt bulb. I guess it is possible that it is a switched neutral at the switch box? When the switch is off there is still voltage in all 4 wires of both light boxes as detected by the voltag sniffer. How accurate are these testers? Thanks..
 
  #14  
Old 04-03-07, 05:51 AM
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I do not think you have a switched neutral. You have told us nothing that even remotely points to that. In fact, just the opposite, everything points to a junction you haven't located where the HOT wire is sent to the switch and switched, just like it should be.

Regardless, stop worrying about it. Find the junction and examine it to see what you have. You need to find it you plan on switching the lights separately, so start looking.
 
  #15  
Old 04-06-07, 11:15 AM
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i would like to offer you the opinion of a person who is not an electrician, but owns an home that looks like it was wired by drunken farmers.

half of the house was built in the 1930's the other half in the 1960's. the older half was built before there was a town, let alone local building codes. it has the style of BX with the insulation that gets brittle and breaks off when you pull a switch out to replace it, which i found out the hard way.

i used to spend a lot of time trying to figure out how they wired the old part, every time i wanted to add something. i too, tested wires and looked for junction boxes, only to discover something very bad and wind up replacing the wire anyway.

my advice is, while i am certain these guys here can figure this out and tell you how to do it, i would just rewire it. run a new wire from the breaker box to the bathroom and then wire it the way you want. you will be a lot happier in the long run.
 
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