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Author Topic: Reliable Circuit Sniffer?  (Read 6601 times)

Rich Grisier

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Reliable Circuit Sniffer?
« on: December 01, 2010, 03:12:05 pm »

I've been looking into a circuit sniffer to tell what outlets are on the same circuit.  Something like an Extech CB10.

From the things I've read, these type of testers result in false-positive readings.  Does anyone have recommendations on testers like this that produce reliable readings?

I'll be using this mainly at venues where the location of the circuit breaker is unknown... and there are four outlets on stage and no one knows if they are on the same circuit.
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Art Welter

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Re: Reliable Circuit Sniffer?
« Reply #1 on: December 01, 2010, 03:42:24 pm »

Rich Grisier wrote on Wed, 01 December 2010 13:12

I've been looking into a circuit sniffer to tell what outlets are on the same circuit.  Something like an Extech CB10.

From the things I've read, these type of testers result in false-positive readings.  Does anyone have recommendations on testers like this that produce reliable readings?

I'll be using this mainly at venues where the location of the circuit breaker is unknown... and there are four outlets on stage and no one knows if they are on the same circuit.

The circuit sniffer requires the sniffer to be at the breaker box and the send unit at the outlet, if you don't have access to the breaker box it won't do you any good.

I found the circuit sniffer I use to be more reliable if the circuit was loaded down than if the  send unit was plugged in alone.
I still would only use it to "get close" to the right breaker, I'd still want to actually turn it off to confirm which is which.

One simple test to see if you have more than one circuit is to check voltage between two hot legs, if the voltage is 208 or 240 you have two circuits.
If the voltage is 0 between them, they are on the same hot leg, though they might be on two different breakers.

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Steve Hurt

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Re: Reliable Circuit Sniffer?
« Reply #2 on: December 01, 2010, 07:54:22 pm »

If someone comes out with one that can be plugged into outlets (not sniffing at the breaker panel) that is accurate every time and easy to use, I'll pay good money for it.

From what I can tell, they don't exist.

The ones that exist are a little bit more accurate than the weatherman.  (They're right a lot, but they're wrong a sizable percentage of the time also)
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Rob Timmerman

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Re: Reliable Circuit Sniffer?
« Reply #3 on: December 01, 2010, 08:07:04 pm »

A voltmeter and an extension cord can tell you with certainty if circuits are on different hot legs (and thus are different circuits).  The same voltmeter and a decent load (1KW or larger) can give you a good idea whether circuits on the same phase are on the same or different copper runs (and thus different circuits).

I would presume that many of the circuit-box style sniffers would also work outlet to outlet.  
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Steve Tarak

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Re: Reliable Circuit Sniffer?
« Reply #4 on: December 01, 2010, 10:37:52 pm »

Want some solid advice? Leave this to a qualified electrician. An Extech is not a reliable piece of equipment. As a former electrician for 12 years, we utilized high level Amprobe / Pasar products which had to be dead on. They were quite expensive and well worth the investment. If you have no experience or training in utilizing these, and by your choice of products I'd conclude you do not, then leave this responsibility to the club owner. Identify something incorrectly, and you may well be held liable.  

my .02

Steve
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Steve Hurt

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Re: Reliable Circuit Sniffer?
« Reply #5 on: December 01, 2010, 11:10:22 pm »

Steve Tarak wrote on Wed, 01 December 2010 22:37

Want some solid advice? Leave this to a qualified electrician. An Extech is not a reliable piece of equipment. As a former electrician for 12 years, we utilized high level Amprobe / Pasar products which had to be dead on. They were quite expensive and well worth the investment. If you have no experience or training in utilizing these, and by your choice of products I'd conclude you do not, then leave this responsibility to the club owner. Identify something incorrectly, and you may well be held liable.  

my .02

Steve


The Amprobe / Pasar products won't determine if 2 sockets are on the same circuit leg w/99% accuracy, will they?
(without access to the breaker box) assuming a qualified operator

<added text to complete question - new text in the parentheses >
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Brian Jojade

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Re: Reliable Circuit Sniffer?
« Reply #6 on: December 02, 2010, 02:56:59 pm »

All you can really tell is if 2 outlets are on separate legs of the supply.  There is no real magic that can, with certainty, tell you if you're on separate breakers.  The reason for this is that breakers are electrically the same as a wire until they trip.  

The most reliable way to determine what breaker an outlet is on is to trip the breaker and see that the outlet goes off.  Sometimes this isn't practical, of course.

Another way to guess if devices are on a different breaker would be to pulse a heavy load on an outlet to cause voltage drop.  Using a small lamp on each outlet, you could see if both dim when you put the load on.  Cheap, and relatively easy to accomplish, but you have to put a pretty significant load, especially if the wiring is short and of high gauge.  This works best in older buildings.

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Brian Jojade
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John Livings

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Re: Reliable Circuit Sniffer?
« Reply #7 on: December 02, 2010, 05:32:52 pm »

Hi Rich,

In addition to the other contributers, I would add the following;

1- Locate the Panel and make sure you have Access to the Breakers of ALL outlets you plan to use.

2- Make Notes and a Diagram of the Circuits  that you will be using.

3- You Have NO simple way of knowing what else might be tied into a circuit unless
it is drawing a load at the time you test it. Repeat, No simple way.( You would have to
trace every wire in every junction box on that circuit back to the Panel)

Calculate your LOAD. This is sometimes called a "Load Schedule"

Enlist the help of someone qualified to help you if you are unsure of things.

Just my thoughts.

Regards,  John
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Rich Grisier

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Re: Reliable Circuit Sniffer?
« Reply #8 on: December 03, 2010, 01:34:20 pm »

Without going into extreme detail, suffice it to say I'm qualified enough to know the difference between volts, amps, watts, vars, pf, single phase, three phase, inverters, choppers, and buck/boost converters.  I know there are times when I need to use my Fluke true RMS meter and other times when my "free with $50 purchase" meter from Circuit Specialists will do just fine.

My main objective was to find out if there was an inexpensive AND reliable way to provide a boolean indication of two outlets being on the same circuit.  My searches came up empty and it appears that is the consensus based on the responses here.

Seems like the old tried & true method of plugging in a light or radio then tripping the breaker is the best inexpensive way to find which breaker services which outlet.  Now, if we could only find someone in the bar to point us to the breaker panel...  Rolling Eyes


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Brian Jojade

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Re: Reliable Circuit Sniffer?
« Reply #9 on: December 03, 2010, 01:39:56 pm »

And, as a service to others, once you identify the circuit, put a small sticker on the outlet with the breaker number.  You'll save the next guy some time that way.
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Brian Jojade
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