Hot Breaker

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The temp. of a three pole breaker is only the beginning of identifying the problem. Where? On the breaker is the heat being generated ? The breaker may be perfectly good with one poor terminal connection? Or maybe two poor terminal connections? Might be a bad bus connection? What is the ambient temp that the breaker is operating at? What i see with these spot monitors is a whole lot of uneccessary breaker replacements. Infrared equipment in the hands of a QUALIFIED operator is good for our trade and our customers. Circuit breakers on A/C and Elevator loads operating close to their rated maximum load WILL BE HOT !! You can change them every time you go back to that panel -- and they will be hot! With good equipment, a qualified thermographer can look at a three pole breaker and see where the heat is being generated, and if the internal fingers of all three phases look uniform in heat generation the breaker is doing it's job!! I owe it to my customers to find their upcoming problems using infrared equipment, but even more important, i don't want them replacing normal operating electrical equipment.
 
Cow said:
Search for posts from Brian John and Fall of Potential testing and you'll find quite a bit of info about it. The trick is knowing how to interpret your measurements.
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If you Google "Fall of Potential", you'll wonder what Ground Resistance Testing has to do with testing a breaker because that's what comes up. I think that it's just confusing to use the FOP term as it's better to say voltage drop test. One may argue about this but the FOP term is normally used when speaking about ground resistance testing.
 
Infrared equipment is pretty danged handy even in the hands of the underqualified. Will I recommend replacement of a breaker because it indicates a certain temp? No. Does it help me in finding loose connections or breakers with a bad pole? You better believe it. FOP has always worked in the past but man I like 6' of distance a whole lot better than 3".
 
ptonsparky said:
Infrared equipment is pretty danged handy even in the hands of the underqualified. Will I recommend replacement of a breaker because it indicates a certain temp? No. Does it help me in finding loose connections or breakers with a bad pole? You better believe it. FOP has always worked in the past but man I like 6' of distance a whole lot better than 3".
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What are you using with that kind of spot ratio?
 
wptski said:
If you Google "Fall of Potential", you'll wonder what Ground Resistance Testing has to do with testing a breaker because that's what comes up. I think that it's just confusing to use the FOP term as it's better to say voltage drop test. One may argue about this but the FOP term is normally used when speaking about ground resistance testing.
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FOp is the correct term, in ground resistance testing the term is 3 or 4 point FOP. It is a little confusing but correct terminorlgy IMO.
 
zog said:
FOp is the correct term, in ground resistance testing the term is 3 or 4 point FOP. It is a little confusing but correct terminorlgy IMO.
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Post a link where the FOP term is used other than ground resistance testing and is used to describe a voltage drop test across a breaker, switch, etc. You can find some but the only place it leads to is this forum. Is there a online FOP calculator like there is a voltage drop calculator?
 
almcvay said:
The unit draws 28 amp all phases. 210 volts at the A/c unit.
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I'm guessing that the 28A measurements were taken while the unit was running with a meter?

Wouldn't this be RLA and not the FLA or MCA? Which would make the FLA around 35A? Breaker would be a 40A - 45A? Checking the nameplate would have been best.

Cycling on and off could increase temperature?
 
ptonsparky said:
Ideal infrared camera. Reallly am at the just starting point but, as you can tell, am pretty impressed. Hate to think what a pro can do with a high dollar unit.
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How high

Saw a demonstration of a very sensitive $25k unit with full HD digital video capture that would trace circuits in a house that was cooled down a few degrees, they just loaded the circuits down a little and you could follow the K&T wire in the wall just like the wall was open, splices and all. Amazing.
Would be great for analyzing a K&T rewire job, but would take a few to pay for itself.
 
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gary said:
What is an FOP?
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To use simple language (which I'm knon to do), measuring Fall of Potential means measuring the voltage across connections and devices that are expected to have little or no voltage drop across them in normal use.

This is used to pinpoint unexpected heat-producing poor contacts and terminations, which are difficult to determine when the equipment is deenergized. In this case, across each pole of the breaker, on pole at a time.

Sometimes, one will find excess voltage between a conductor and its lug. Start with the voltmeter set at a medium voltage range, and reduce it as you narrow down the hot spots. (Don't switch ranges while reading.)
 
hurk27 said:
How high

Saw a demonstration of a very sensitive $25k unit with full HD digital video capture that would trace circuits in a house that was cooled down a few degrees, they just loaded the circuits down a little and you could follow the K&T wire in the wall just like the wall was open, splices and all. Amazing.
Would be great for analyzing a K&T rewire job, but would take a few to pay for itself.
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C'mon Wayne, don't leave us hanging:grin: What camera was being used????
 
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