Finding household wire

I bought a timer kit to use in the laundry room as I always forget to turn the light off and electricity isn't getting any cheaper.

The wiring in the house is tube and knob so wiring the switch is going to require me to find the neutral wire for the light wiring. I got back in the basement and found a few suspects but I want to make sure I tap into the right wire before I do any cutting. Basically I have to tap into the neutral so the time switch gets a trickle of juice and stays happy. I guess the timer in the switch uses electricity to control it, this means the switch basically has all the goodies, a ground, neutral, and hot wire verses the old switch which is just two black wires without a ground.

My question is what would be the best way to find the suspect wire? I can poke it and check for continuity but that is kind of a pain and I want to do non-destructive testing. I know I can get a clamp meter but wanted to know if there is another way to find the neutral wire in question.

Thanks folks!

This works well for finding wires. I use one at work regularly.

http://www.harborfreight.com/catalogsearch/result?category=&q=wire+tracer

Ok so a clamp meter is the hot ticket. Another job another tool right?

Maybe I can get the fluke 322 for cheap someone is selling on CL, we will see, but for 20$ that seems nice and cheap.

yikes

Yikes is right.

A $20 Fluke is stolen or broken.

I earned a living with a multi-meter for, I dunno, close to ten years, I guess. I use one that I bought at Walmart for about $10. I think they're $15 to $20 now (the inflation we didn't have). IN GENERAL, the neutral will be the same electrically as the ground. With your meter set to Volts AC, put one lead on one wire and with the other lead, touch ground. Read anything? If yes, that wire is hot. If no, that wire is neutral. Probably.

You know you can get a wind up timer switch at Lowes, right? That's what I used to make a timed light bar so I wouldn't burn up my cheap-o HF cordless drill batteries with the super-cheap chargers they come with. You just wire that in one leg (usually the hot one, but house wiring can be strange, especially old house wiring) in place of a regular switch. Cheap and easy.

You can also get motion sensors that screw in between the light bulb and the base. Then you don't need to touch that stuff.

No the guy wants 100$ for the fluke model 322. I like that one though because it will reads DC and has a range switch for low amps like most of the stuff I'd be doing. Fortunately none of my vehicle have any electrical issues, yet so maybe I don't need to be able to read DC volt/amps. I don't think I need to read 600amps unless I decide to bypass the electric company and go straight for the power pole.

I meant the cheapo 20$ Harbor Freight one might fit the ticket, but for some stuff I error on the side of quality, measuring and cutting tools come to mind.

The problem with using a regular multimeter is I'd have to nick into the wire to get at the conductor, with the clamp thing I just clamp it on the wire and have someone turn the light on and off. I will observe a fluctuation in amperage if I'm looking at the right circuit. Then I just tap into the neutral and wire up the switch.

This is basically how every job I've ever done works, messed up. Last week I went to put in a door knob that I got from a thrift store. First off the latch was missing. Went to house recycling place and find the latch, same make. Got to put latch into door, it is an outdoor latch not inside. Meaning it is about 1/8" larger than the other lock latch. By now I'm getting pissed, bore out the door to make the latch fit. Now I realize the housing for the latch also won't work with the larger outdoor latch. A smart person would have quit, but Mr. Determine takes out the hacksaw and 30 minutes later the latch fits into the housing. A 15min job for me = 2 1/2hours.

Although the last clamp on meter I used was amps only and over 30 years ago, I don't think the clamp on thing is going to tell you the hot wire from the common. They both have the exact same everything flowing through them.

All meters you buy today, even $1 HF ones, will read DC. I think you need a little assistance with this one. Even a knowledgeable but not professional local friend. "Messed up" and "electrical" are a bad combination.

Agree with Dr Hess. Old wiring has, along with the obvious age and weirdness compared to modern systems, an additional component of possible well meaning but poorly executed modifications and repairs over the years. I have seen some really weird stuff in old houses I have rented.

Then there is the lack of a ground circuit on the old systems. That can mean the difference between life and death for both you and your electronics.

I think the motion sensor thing Hocrest mentioned is probably your best bet.

The HF meter I posted is a wire tracer. Shut the circuit off and attach the little box with the alligator clips to the wire. The bigger unit has a sensor that you hold near the wire. If it is the wire you are looking for it will beep. If not, no beep. If you hook it to the neutral in the panel, the neutral you are looking for will beep. No need to damage the wire. It will read through the insulation. I have used mine for several years to chase wire all through hospitals where I need to find one wire out of hundreds.

The wind up timers posted earlier would be good too. They are mechanical and you won't need a neutral to power it. Your local hardware store probably carries them for less than the cost of the wire tracer.

Hire an electrician!! Wiring isn't a hobby,and you can hurt yourself working on it if you don't know what you are doing. Also you could burn down your house which is really bad. Knob,and tube wiring is a safe system,but remember sometimes they also put a fuse on the neutral wire,so just chasing the wire will not always tell the whole story. A licensed electrician can do it for you real easy I bet,and it will be safe. Or just remember to shut off the light. I mean how hard is it to remember something like that?

pete240z wrote: yikes

Lemme get this straignht, THIS type of wiring is still legal?? AndIi freaked over seeing some fabirc covered wiring in this building.

Mazdax605 wrote: Hire an electrician!! Wiring isn't a hobby,and you can hurt yourself working on it if you don't know what you are doing. Also you could burn down your house which is really bad. Knob,and tube wiring is a safe system,but remember sometimes they also put a fuse on the neutral wire,so just chasing the wire will not always tell the whole story. A licensed electrician can do it for you real easy I bet,and it will be safe. Or just remember to shut off the light. I mean how hard is it to remember something like that?

I'll have to disagree on this one. House wiring is easy. If you have a brain cell in you head you can do it. Yes it can kill you, yes it can burn your house to the ground, but no more so than fixing the brakes or the fuel system on a car can kill you or burn your car to the ground. Use your head and if you have questions ask. Post and tube make it a little different than the usual romex, but the principles are the same. I would probably update it while working on it if it was me. Romex and plastic boxes are cheap.

I've done some wiring before and the house hasn't caught fire yet. From what I understand you will not be able to measure voltage on the neutral wire as it is grounded. The voltage difference between the hot and neutral is what allows you to run an appliance on the wiring. Measuring the voltage on the live wire doesn't tell me anything about where the neutral wire is, for that you measure amps. The return of electricity through the neutral wire is monitored by the amount of amps that pass through it and you cannot measure voltage because there isn't any voltage in the neutral wire. If the neutral wire was 120V you wouldn't have any potential and nothing would happen when you turn on the light switch. If I don't wire it correctly the light switch will not work, that simple. Because the neutral wire is grounded it means I should be able to tap into it and unless I come across a live wire there isn't a shock risk involved. I already found the circuit breaker for the switch so that will be off.

If I was to wire in a 40amp breaker for the welder or something remotely dangerous I'd step back but this small stuff doesn't scare me much.

The old fuses got replaced with a proper breaker box so one less thing to worry about.

Disagree all you want,but it is still the best advice anyone can give. I have a license,and I hate seeing what homeowners,and handymen do with wiring in houses. They make you work for a long time in this industry(8k hours here in MA plus classroom time) before they allow you to get a license for a reason. Electrical work is dangerous,and can lead to fires,and death. Not something to be taken lightly.

The difference with a car burning to the ground,and your house is that you most likely won't be asleep in your car when it starts. Brake work is a legit argument,but most of the time you will have a warning before the brakes let go,and you should also have another means to stop the car as well. Do what you want,but I still say hire someone who knows what they are doing. If this were a simple install of a timer in an existing locating that didn't require you to identify what is what with K&T then I would say yes have at it,but be careful,but not in this case.

By the way to the poster who asked about the legality of the K&T wiring. Yes it is legal still(not for new install,but grandfathered as acceptable),and yes it is actually a quite safe means of wiring,if not a bit antiquated with a lack of a secondary ground like modern wiring. The other thing that blows peoples minds is that in my opinion,and many others,fuses are the safest thing you can have in your house. Insurance companies don't see it that way,but in my opinion the simple fuse is way more safe as it isn't a mechanical device like a breaker that can break down over time,and then not work when it is needed.

I picked a voltage detector from lowes http://www.lowes.com/pd_169-72068-GT-12_4294820986_4294937087_?productId=3095845&Ns=p_product_prd_lis_ord_nbr|0||p_product_quantity_sold|1&pl=1&currentURL=/pl_Test%2BMeters%2B_4294820986_4294937087_%3FNs%3Dp_product_prd_lis_ord_nbr|0||p_product_quantity_sold|1

found the hot wire, other wire would be be neutral then except for 220 lines.

my fieldpiece meter tells me which is which, because when you cross up the leads it reads negative voltage.

i found the best solution for knob and tube, because of years of homeowner fix its and add ons, is that i rip it all out, scrap it, and pull new romex everywhere.

AC doesn't have a negative, Pat.

I have access to about 1/3 of the wiring to the house so it is a possibility to pull new romex 3 wire. I really don't want to go too deep though, maybe in the mean time I'll work on adding a few ground where I have access to the pipes and wires.

I definitely know what you guys mean by wanting more modern wiring. The only thing I really don't like about the tube and knob is that there isn't a ground for the outlets. Running individual grounds is a pain, but if I'm going to go dick with something I might as well add some value.

The house did have the fuse box removed and a breaker box put in for insurance reasons.

What I fear most about that old wiring is that it's old, meaning more opportunity for jackleg repairs. I have been shocked by ceiling grid that had come in contact with a bare wire, have crawled an attic and had a junction box explode right by my face, and more scary stories. I really suggest an electrician. I recently needed 20' of conduit and a new outlet to be installed. Called a pro, even though I knew how to do it. 100.00 well spent.

Good advice cwh.

Believe it or not, that picture is not necessarily unsafe.

The problems with K&T wiring are that:

a) it is old, and therefore modified in untold (and unpredictable) ways. Time has certainly deteriorated insulation, and bad remodeling has certainly tied circuits together in inappropriate ways. Poorly done splices, badly run wires, and improper circuitry all exist (I didn't say they CAN exist, they DO exist). The K&T wiring is grandfathered (it was legal when it was installed). The changes are generally not (because they were not ever legal).

b) it is ungrounded. Particularly inappropriate for modern electronic systems.

It you have the option to run a new (properly grounded) circuit of romex the whole distance (full run back to the panel) do it.

Thank you for all the suggestions folks. I'm not going to get to either finish or abort this project until after the holidays. It is raining like hell and I don't want to be standing in water while working with wiring, a man's got to know his limitations.

I like the idea of finding an electrician because I want to have a high amp circuit wired in for the welders and compressor. I really should just convert to 220V though.

I found this bitchin cheap clamp meter I think I'm going to buy. For 50$ you can't beat it.

http://www.amazon.com/Sinometer-Manual-Clamp-Meter-BM802/dp/B000LY4UBA

Thanks again.