I live in an old house which was once apartments (had 5 meters removed and fuse boxes replaced with a service panel but no work done on the wiring itself). A friend of mine has been helping map the circuits to see what all I've got running what and what options I might have for adding wiring for a few things or separating circuits (so the bedroom AC doesn't flip the breaker for the microwave, for example). At one particular switch, for a circuit that has only ceiling lights (total 7 fixtures; I use CFLs everywhere) the voltage tests consistently at 69 volts. Any idea? At the same switch, we found a jumper wire connecting it to an adjacent switch which is for a completely different circuit--we removed that wire. Not sure if the 69 volts was both before and after removing the jumper wire.

 

Welcome to the forums.


Yes......start over.

You live in an old house that once had five meters and five fuse panels. Now there is just one meter, one panel and a mess of wiring. It sounds like you're going to have your hands full identifying wiring in that building.

 

I am with PJ max on this one. You do not want to deal with that old mess. Start over.

 

Welcome to the forum.
Unfortunately I'm with the other guys on the start from scratch bit.
The voltage you are pulling would scare the crap out of me. Something really isn't right and you could be looking at a fire starter electrical system.
Depending on the age of the house, and how the electrical was upgraded over the years, you could very well find knob and tube wiring, alluminum wiring, copper, or a combination of any of these.
The fact that your microwave plug and a bathroom outlet are attached does kind of make sense. I have seen this done before (not a bathroom and kitchen however). Kitchen appliances generally have high demands so I've seen circuits split between those outlets and less demanding outlets. May not be acceptable in all areas, so keep that in mind.

 

Poor probe contact or an improper ground reference could explain the low readings.

Since you are redoing things you are going to need to meet the currently enforced codes in your area. Dedicated circuits, GFI and AFCI protection, required receptacle spacing are just some of the issues you will need to deal with.

 

"Start over" could mean anything, you know? I've been in this house 12 years and complete rewiring is not financially feasible. BTW it's a bedroom--not bathroom-outlet and kitchen microwave. We use pretty minimal electricity (except for the electric boiler, which is very new but wretchedly expensive to run in ND winters and of course has all its own wiring), and that microwave-AC breaker is the only one that ever flips (because I forget to check if the AC is running in that room before nuking a cup of coffee). In the kitchen, where I have an outlet on a different circuit that only has 2 other outlets (one of which is used for a 60w plant light in winter and the other very occasionally a stereo console), I use that outlet for fridge and countertop appliances but only one appliance at a time and use a surge protector with built in breaker (which will reset if I forget and turn on an electric skillet while coffeemaker is on--the fridge is very new and the smallest regular fridge I could get due to the kitchen size). I was mostly wondering about the electrical explanation for the voltage reading on those wires. It's a branch wire, some of the old wiring had junction boxes but some of the junctions were just spliced and taped. Now that we know everything that comes off the circuit we should probably test every switch and light fixture to see if it is just that branch, does that make sense? No aluminum wiring has turned up anywhere but attic has some knob and tube which connects to second-floor bedroom. We also pulled a 5.5 reading (consistently) on a circuit with breaker off but found an explanation for that (inductive source on the line, need to retest with possible sources unplugged).

 

Yes, two: One is that testing for voltage should always be done by putting the probes in contact with a pair of disconnected. Testing with one probe on the terminal of a switch that may have a connected load is likely to result in an incorrect reading.

Two, use an analog multimeter. In general, digital multimeters do not filter out induced voltage as analog multimeters do. The 69 colts you saw might not be line voltage.

To ensure that you are checking line voltage to a good neutral and a good ground, you can plug an extension cord into a receptacle that you know has all three conductors in good working order and, at the wires you're testing, test from the hot wire in the wall or ceiling to the neutral slot and to the ground slot in the female end of the extension cord. It's a good way to spot a problem with either the neutral or the ground at the location where you're testing.

It sounds like adding the required kitchen circuits might be a good place to start. A dedicated 20A circuit for a built-in microwave and the two dedicated, GFCI protected small appliance branch circuits for the countertop receptacles come to mind just from reading this statement. Then there's the refrigerator, dishwasher and garbage disposal, without getting into the 240V circuits for cooking, if you need those.

Mapping the existing circuits in a house, particularly one that's older and/or has had its wiring modified over the years is always helpful. Keep an eye out for circuits that have more than 6 or 8 receptacles.

Wiring Simplified is an authoritative, inexpensive and readable reference for understanding and working on a residential electrical system. You may find it in the electrical aisle at your local home improvement center.

 

If I am understanding you correctly, the problem is the probe contact or the neutral--but could the problem be from the hot side?

 

I have no idea what the problem is. It could be in the wiring for the ungrounded conductors (the "hot side"), the grounded conductors (the "neutral), the type of meter you're using, the way you're using the meter, or any combination of those.

What I wrote was some tips to help you make sure that you are getting good, reliable readings as you test. Getting those is the only way to have useful information. Anything else will be meaningless or, worse, confusing and misleading.

Do the lights controlled by the switch where you saw 69 volts work as they should?

Adding new dedicated circuits where those are required, and separating those loads from any other loads in the house, is a good place to start, regardless of any testing.

You should only keep and re-use existing wiring if is as good as the wiring you would use to replace it. Make sure it's the correct gauge, undamaged, and has an equipment grounding conductor (a "ground wire").

 

FYI, Microsoft Excel has a built in flowchart option.
I found it was quite helpful to do a simplified layout of the wiring in a 200 year old farmhouse.

I also found that the only practical way to trace the ACTUAL path for the circuits
(e.g. from box, down 3rd basement beam, along center beam, out along 10th beam...)
was to have only one circuit per sheet of paper - trying to keep track of multiple actual paths is
almost impossible to keep separate.

 

Interesting. I've never tried that.

I always map each room as I go. The first step is to draw a floor plan and add the symbols for the lights, switches and receptacles to it. After that, it's just a matter of noting the circuit for each device next to its symbol.

 

Eh, I think we're talking about slightly different maps.

If you're doing a logical map of which outlets / fixtures are on each circuit,
I agree, go room by room.

I'm talking about doing a complete "from the panel, each wire, each junction box, each outlet" inventory.


Yeah I know...
Why?


Because I found about 100' of old wiring which had been disconnected and abandoned in place over the years.

 

Possibly we are. The map or drawing I'm interested in is the one that lets me get the system into shape to safely do what I, or my client, needs it to do. I don't see how a linear map of each circuit would help me do that.

I have intuited such a schematic, once of twice, when the problem was too many devices on a single circuit. But that was done from the map of the devices.

Interesting. What did you do with it?

BTW, I think we're wandering off topic here.

 

Was mostly unusable - late 1940s flex/greenfield armored 2 wire,
cloth and post war rubber insulation was too brittle to do anything with.
Guess I could have made a H.R. Geiger x-mas wreath,
it went to the local scrap scrounger.

Did find some excellent condition pre-war cloth and gutta percha phone wire,
excellent condition, set those aside for wife's friends who do WW-II re-enactments.

Really surprising how well the 1930s pre WW-II rubber insulation holds up
compared to the post-war 1940s stuff.