ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat Box
Recent Posts
Happy Thanksgiving
by electure - 11/26/20 08:45 AM
Ground fault remover :-)
by NORCAL - 11/26/20 08:13 AM
Work Gloves?
by sabrown - 11/25/20 01:54 PM
Insulated Tools: A Waste of Money?
by sabrown - 11/25/20 01:52 PM
What does your work place look like?
by Lostazhell - 11/25/20 02:56 AM
New in the Gallery:
Facebook follies, bad wiring
FPE in Germany pt.2
Who's Online Now
0 registered members (), 17 guests, and 16 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Page 1 of 2 1 2
Counter EMF #208014 12/19/12 10:07 PM
Joined: Jul 2007
Posts: 1,335
S
sparkyinak Offline OP
Member
Break out the pocket protectors and slide rulers for this one. How much CEMF is acceptable in a lighting circuit? I'm trouble shooting a lighting system thats all track lighting. Recently a section burnt up at the coupling and the track, and it supposed a good quality track. Due to its troubled history, I am looking at every angle.

In my research and testing, I discovered a slight unbalance of 0.15 amps via amp clamping all the conductors in the conduit without the grounding couductor.

Is there a way to quantify the resistance of the circuit that is unbalanced? There are two circuits in the conduit with its own grounded conductor. The circuit that the track failed has no measurble CEMF. The second circuit is the one that is reading 0.15 amps. Being that it is in the same conduit as the ciruit that failed, It will affect it some. The big question is is the affect big enough to be concern about?

Any takers onm this one?


"Live Awesome!" - Kevin Carosa
Work Gear for Electricians and the Trades
Re: Counter EMF [Re: sparkyinak] #208015 12/20/12 12:02 AM
Joined: Apr 2002
Posts: 7,216
HotLine1 Offline
Member
Gut tells me that you may be overthinking. What I had over many years with track (commercial) was the coupling and/or live end burnouts were results of a poor contact connection.



John
Re: Counter EMF [Re: sparkyinak] #208017 12/20/12 01:05 AM
Joined: Feb 2004
Posts: 1,435
Lostazhell Offline
Member
Even though we may look at a manufacturer as being high quality, they're still bound to occasionally throw a weak product out there. The couplings/wiring connectors are usually the weakest link in any track lighting set up. Most track I've come across is rated for 2400w but I've never pushed any near that far... I've seen receptacles that can be snapped into lighting track just like a fixture, leading me to believe the mfrs have quite a bit of faith in the stuff..

Re: Counter EMF [Re: Lostazhell] #208018 12/20/12 02:53 AM
Joined: Jul 2007
Posts: 1,335
S
sparkyinak Offline OP
Member
It's not a case of over thinking. I'm confident in my findings. It's a trivial question at best. I'm addressing every possible angle of failure for a report. There is a long history with this system. If it is not documented, it did not happen. I'm just trying to quantify all my findings for my report.

The question is more about CEMF and its affects and less about the track lighting


"Live Awesome!" - Kevin Carosa
Re: Counter EMF [Re: sparkyinak] #208019 12/20/12 01:29 PM
Joined: Mar 2004
Posts: 947
T
twh Offline
Member
0.15 is a small amperage. If you are using a clamp meter, it would be tempting to test the accuracy by doubling the loop through the clamp.

If there is a fault to ground, 0.15 amps at 120 volts is about 18 watts. That much heat should be detectable by touch if it all happens at one place. You could try a megger at 250 volts to confirm the problem and pull the lights off the track to eliminate them as a cause.

0.15 amps to ground at 120 volts suggests a ground fault of about 800 ohms, or two faults of about 1600 ohms. It isn't hard to imagine a couple or two with dirt or arcing to be the cause.

I also had problems with track lights that failed at the couplings. It turned out that the ceiling moved when people walked on the second floor.


Re: Counter EMF [Re: sparkyinak] #208024 12/20/12 10:21 PM
Joined: Apr 2002
Posts: 7,216
HotLine1 Offline
Member
sparkyinak:

I have to agree with what Lost & twh said. I meant no offense to you regarding the 'overthinking'.



John
Re: Counter EMF [Re: HotLine1] #208030 12/21/12 04:27 AM
Joined: Jul 2007
Posts: 1,335
S
sparkyinak Offline OP
Member
None taken, john. Just clarify the intent of the OP smile

Last edited by sparkyinak; 12/21/12 04:28 AM.

"Live Awesome!" - Kevin Carosa
Re: Counter EMF [Re: sparkyinak] #208055 12/22/12 08:40 AM
Joined: Jun 2004
Posts: 1,273
T
Tesla Offline
Member
Back EMF I've heard of.

Counter EMF is new to me.

I'd prefer to name it impedance.

Unless you've got ultra special bench test gear -- 0.15A is within the tollerance for error on every piece of field test equipment I've touched.

As for track lighting issues: IMHO they all have touchy joints/ connections.

The actual conductors are thin rails of copper -- sometimes tinned -- but definately not designed for really heavy loads.

Which is to say, that they can mount more loads than their intrinsic bus can carry -- without heating up to a fine glow.

Also, I've run into ancient age resistance style voltage controls/ dimmers that make everything worse -- much worse.

Good luck.



Tesla
Re: Counter EMF [Re: Tesla] #208058 12/22/12 01:29 PM
Joined: Jul 2007
Posts: 1,335
S
sparkyinak Offline OP
Member
Let me rephrase my question. Taking the track light out of the equation, how much CEMF, or back emf is too much to cause problem like wires overheating? For example, there is 5 amps unbalance measured in a circuit. It there a way to calculate the impedance of the circuit based on that 5 amps measured?


"Live Awesome!" - Kevin Carosa
Re: Counter EMF [Re: Tesla] #208060 12/22/12 02:55 PM
Joined: Mar 2004
Posts: 947
T
twh Offline
Member
Originally Posted by Tesla
Back EMF I've heard of.

Counter EMF is new to me.
Counter EMF, here, is the term used to describe the voltage created by a running motor, which is counter to the applied voltage.

Page 1 of 2 1 2

Featured:

2020 National Electrical Code
2020 National Electrical
Code (NEC)

* * * * * * *

2020 Master Electrician Exam Preparation Combos
2020 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Member Spotlight
Grover
Grover
Sebago, ME, USA
Posts: 109
Joined: January 2005
Show All Member Profiles 
Top Posters(30 Days)
Trumpy 9
Popular Topics(Views)
271,960 Are you busy
205,849 Re: Forum
193,925 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.7.3