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#69995 - 09/27/06 06:00 PM Finding hots associated w/common neutrals
jfwayer Offline
Member

Registered: 05/15/05
Posts: 30
Loc: Fairmont, WV, USA
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
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JFW

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#69996 - 09/28/06 04:15 AM Re: Finding hots associated w/common neutrals
jkraft Offline
Member

Registered: 05/05/03
Posts: 75
What do you use for the flashing load?

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#69997 - 09/28/06 04:42 AM Re: Finding hots associated w/common neutrals
Tiger Offline
Member

Registered: 05/04/05
Posts: 714
Loc: Crystal Lake, IL USA
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

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#69998 - 09/28/06 05:14 AM Re: Finding hots associated w/common neutrals
SteveFehr Offline
Member

Registered: 03/19/05
Posts: 1192
Loc: Chesapeake, VA
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).]

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#69999 - 09/28/06 06:42 AM Re: Finding hots associated w/common neutrals
renosteinke Offline
Cat Servant
Member

Registered: 01/22/05
Posts: 5305
Loc: Blue Collar Country
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.

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#70000 - 09/28/06 11:37 AM Re: Finding hots associated w/common neutrals
mxslick Offline
Member

Registered: 10/24/04
Posts: 785
Loc: Atomic City, ID USA
 Quote:
They are limited to 60 amp loads.


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?
_________________________
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#70001 - 09/28/06 12:30 PM Re: Finding hots associated w/common neutrals
wa2ise Offline
Member

Registered: 11/29/02
Posts: 771
Loc: Oradell NJ USA
 Quote:
That'd be one heck of a large button flasher..for mogul base sockets, right? :-)


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

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#70002 - 09/28/06 04:08 PM Re: Finding hots associated w/common neutrals
renosteinke Offline
Cat Servant
Member

Registered: 01/22/05
Posts: 5305
Loc: Blue Collar Country
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?

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#70003 - 09/29/06 12:24 AM Re: Finding hots associated w/common neutrals
skipr Offline
Member

Registered: 01/03/05
Posts: 41
Loc: Huntington Beach, Ca.
seems like a Amprobe AT-2004 advanced tracer should do just fine.

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#70004 - 09/29/06 04:27 AM Re: Finding hots associated w/common neutrals
32VAC Offline
Member

Registered: 06/28/04
Posts: 203
Loc: Alice Springs, NT, Australia
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.

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