I'm working for a school system with 20+ buildings of various ages from 100 to 0 years. Many of the fuse and panel boards are not marked or incorrectly marked. We've been having trouble adding outlets and lights to circuits with shared neutrals in 120/240, 120/208, and 277/480 configurations. I'm looking for a method to determine the origin of a circuit and the other hot wires associated with the shared neutral. Are there any trick ways.

My current idea is to make a flashing load of several amps, connect it to the circut. Then go back to the expected panel board and look for wires that amprobe at the flashing rate. This should id the hot and neutral for the target circuit. Then I grub in the panel board for other hots associated with neutral. AssUme'ing no one's tapped a random neutral wire in a junction, I've found the hots and neutral.

I'd like much easier way... if it exists.

Thanks,

Jim Williams

What do you use for the flashing load?

That sounds like the easiest way to me. You can do this hot. Otherwise you might disconnect the wires & do continuity tests, but that won't be quicker.

Dave

There are cable clamp signal generators made specifically for this- you clamp them at one end and walk along with a trace probe which can track them through walls. We use them all the time for tracking data cables; I've never personally used one for power cables, but I've seen them, our one meter had clamp attachments for it and probes for finding leakage from broken underground cables too. There is some issue with bleed-over to other nearby circuits when it branches out, but the signal is always attenuated on the other cables, and strongest on the one you're tracking.

If you know where the cable end points are, your solution sounds easiest. In fact, I did the exact same thing last week- used a small microwave (manually) pulsed on and off to verify which circuit breaker was feeding the string. A 10A pulse is hard to mistake!

[This message has been edited by SteveFehr (edited 09-28-2006).]

A flashing load is made by getting one of those old-fashioned "buttons", and inserting it in the socket under the bulb. They were once common for Xmas displays- and are still available. They are limited to 60 amp loads.

The problem with using several at once is that there is no way to have them trip in time with each other.

Still, the 1/2 amp fluctuation is useful in finding circuits.

I have also found the usual circuit toners to be useful in finding the appropriate neutral in the panel.

Adding a large load, as with a space heater, might also help find the right wire.

That'd be one heck of a large button flasher..for mogul base sockets, right?

I'm just gonna take a stab-lok here, you really meant 60 watt?

Maybe that flasher is what is used to drive those broadcast transmitter towers flashing red lights?

MX... I sure did mean 60 WATT! I'd go back and edit, but then, everyone would be confused by your post.

OOPS!

Guys, my e-mail is in my profile. I make a stupid goof like this again... and Mr. Murphy says I will... how about just dropping me a line?

seems like a Amprobe AT-2004 advanced tracer should do just fine.

I use a 1200 watt bar heater which gives me 5.1 amps @ 230 volts. Put the clamp meter on the circuit, take a reading, switch the heater on, if it goes up 5.1 amps, you're on the right circuit.

Another usage of the flasher button behind a light bulb is for finding the circuit that the computer is fed from. That way you can vividly mark it so that the 'puter does not get accidentally turned off, either by your apprentice or the next guy.

What about the heater hooked into some sort of remote control relay? I can't imagine the compentents off hand. Any suggestions? RadioRa? Car alarm key clicker with a 12V relay controlling a 120V relay?

What about the heater hooked into some sort of remote control relay? I can't imagine the compentents off hand. Any suggestions?

A helper with a Nextel. Always amazes me what people will go through just to work alone.

-Hal

[This message has been edited by hbiss (edited 09-29-2006).]

Hal,

If he uses Nextel, he may not reach his helper, in the next room!

I use a 1.2 / 2.4 kW fan heater which is switched on and off via a 20 Amps IPR relay, which is driven via a 1 second electro mechanical timer.
( just a synchronous motor with a camwheel which turns around in 2 seconds ) which turns it on for one second and turns it off for one second and so on.
It gives me a pulsating test load from 4.8 or 9.5 amps, and works very well

I've done simular things with another guy revving a skil saw - the one jumping ~7a is the one.... It's quicker than hand over hand tracing, or toners that can ring into the whole panel, or other panels. (And once into another building on the same tranny.) It is noisey though, and works the same with other high starting amperage tools/motors that are less noisey, but it being loud helps to know when it is on, and when off. You can also here the motor starting in the toner reciever. Never really thought of automating it, past the initial thought, just never got around to it... But would it not be neat to have a product that toned / traced, and did this Amp Jump too? I have also written down all the values (no extra load), and then check again with the extra load..

Hal, I agree with LK, nextel can delay the whole proccess, a regular walkie talkie is better.

They have RF remote controlled "outlets", hat basically have the RF receiver/decoder directly controlling the relay which the load passes, with a small remote.

I have done the Car remote/receiver (car alarm) to SSR, to control some contactors thing before.

"What about the heater hooked into some sort of remote control relay? I can't imagine the compentents off hand. Any suggestions?

A helper with a Nextel. Always amazes me what people will go through just to work alone.

-Hal

[This message has been edited by hbiss (edited 09-29-2006).]"

Small minded one size fits all comments always amaze me. We have 8 electricians and two apprentices just in our service department, so obviously an apprentice to help each Jman for every job is not going to be possable.

Several companies make some High Quality circuit tracers now a dayz, We just got one that will trace a hot circuit from 6v up to 600VAC, it also has a clampon unit for to trace from the panel back to the loads.
wasn't cheap tho.........