Three times a charm

[Robert J. OConnor]

Originally Posted by cbottger

I load tested the panel ...

I would be very careful with that wording, since you are just doing a visual inspection with a good number of circuits on.

To properly load test breakers you have to significantly exceed the rating under controlled condition (e.g. 135% and 200% of the rating following UL standards). If the 50A breaker in question didn't trip, even at a load around 60A, it tells you absolutely nothing about the reliability of the breaker. Breakers can trip anywhere from 100% to 125% of the rating. A breaker could be loaded to 120% of the rating without tripping or there being anything wrong. See this discussion, which also has an example breaker trip curve ...

http://forums.mikeholt.com/showthread.php/134611-FPE-Breaker-Amperage-amp-Time?

So for an FPE panel you are back to square one with it being a problem right off the bat from an HI's point of view, since they have a known history of problems with breakers not tripping when they should, and issues with poor bus connections.

JMO & 2-Nickels ...

[Chuck Evans]

Originally Posted by roconnor

A breaker could be loaded to 120% of the rating without tripping or there being anything wrong. See this discussion, which also has an example breaker trip curve ...

http://forums.mikeholt.com/showthread.php/134611-FPE-Breaker-Amperage-amp-Time?

We recently had this discussion over on the NACBI forum (that's a 15amp OCD in the photo and it never tripped while I was present). Jim Seffrin provided some very useful information http://www.nacbi.com/messageboard/sh...15-Amp-Circuit

[Chuck Evans]

Originally Posted by pabernathy

Notice that THHN in as limited to 75 degrees due to terminal ratings has an ampacity of 200A for a 3/0 CU. Notice the acceptable temperature of the conductors at that degree rating...167 degrees F. Without going into too much detail as I would find it hard to explain it here....it would not be a problem to see a conductor with a temperature not exceeding that value.

Don't want to get too technical....just want to kinda explain it just a little.

I agree in absolute terms.

But elevated temps observed at fractional loads may well indicate a thermal exception when adjusted for full load. For instance: the 200A rated THHN circuit at an 80A actual load in 70F/21C ambient with an observed temp of 150F/66C would be considered a thermal exception.

[Linas Dapkus]

Originally Posted by cevans

I agree in absolute terms.

But elevated temps observed at fractional loads may well indicate a thermal exception when adjusted for full load. For instance: the 200A rated THHN circuit at an 80A actual load in 70F/21C ambient with an observed temp of 150F/66C would be considered a thermal exception.

So what is the formula for calculating Absolute Temperature Criteria and where can this information be found?
Good luck with your Level III training this week guys!

[Paul Pendley]

Originally Posted by cbottger

Nope a visual inspection only camera in hand with amp meter Joe don't start that SOP crap with me we both know better

I thought anything outside the SOP would be considered a technical inspection and not within the guidelines of a standard home inspection.

[Robert J. OConnor]

Originally Posted by cevans

... that's a 15amp OCD in the photo and it never tripped while I was present

The load usually has to be about 125% to 135% of the breaker rating to ensure a breaker trips (some trip at lower values).

So even with an 18A load on that 15A breaker there likely is nothing wrong with the breaker. The capacity of the entire circuit likely needs to be upgraded or some load removed ... but thats not a problem with the breaker. Some are amazed at that.

And I would recommend www.mikeholt.com for more information. Excellent site, tons of good info, with a lot of really knowledgeable people.

[Chuck Evans]

Originally Posted by ldapkus1

So what is the formula for calculating Absolute Temperature Criteria and where can this information be found?
Good luck with your Level III training this week guys!

Hey Linus. That's Level-II (quantitative thermography) based on the absolute temperature criteria from the Infraspection Institute Standard for Infrared Inspection of Electrical Systems & Rotating Equipment.

Thanks for the well wishes. Class is going great!