I inspect FP panels almost on a daily biases and If I must say so I am dam good at it practice makes perfect.
Here is an example of a bad one found recently. I do not condemn just based on the name Federal Pacific I judge each panel independently.
This panel was inspected in January by another inspector and he just condemned based on the name which in turned brought out the electrical contractor who inspected it again and put in writing the panel was just fine.
These first two inspections were brought about as the result of a re-location company purchasing the property my inspection was for a perspective buyer. I load tested the panel with in house circuits and built in appliances and exceeded the 80% rule again. The top left breaker was for the cook stove rated at 50 amps the cook stove drew 49 amps and tripped the breaker but by looking at the breaker could not tell it was tripped. So after 3 inspection this home appears to be getting a updated panel.
My client was very happy and after speaking with the selling RE agent I could tell by the sound of her voice which was very quite she was not to happy with the outcome. How do I know this just from the tone of her voice I have been sleeping with her for almost 43 years yes all is disclosed up front and on the table:D:D:D
80% of the rating of the panel the 100 amp panel should not carry more than 80 amps. I start looking for problems when the temp is 30 degrees above ambient of the panel also I look for an un-balanced load temp wise on a 220 volt double pole breaker both legs should be almost the same in temp
I would question the use of 80% as a rule. Sounds like a good guideline but it’s not supported by the NEC. A panel can be loaded to 125% of it’s continuous load plus 100% of it non-continuous load. In a dwelling just about every load is non-continuous with the exception of some lighting loads. A cook top on a 50 amp circuit running at 49 amps is OK according to the NEC.
So Robert you are telling me say take a 200 amp panel in today’s world and load that baby up to 200 amps continuously full load and that is perfectly fine. According to NEC
No, that would be 200 amp non-continuous. The NEC definition of continuos load is that it is operated at it’s maximum ampacity for 3 or more hours. So if you use your range as an example it is permitted to operate at 49 amps on a 50 amp circuit because it will never operate at it’s maximum for 180 or more minutes.
The 87.9 amps on the 100 amp breaker was what my reference was about and the 87 amps could be in use for many many hours especially on a heavy cook day like thanksgiving. I have never been questioned about exceeding the amp draw by 80% for extended time or the capabilities of extended time.
The breaker tripping on the cook stove at 49 amps within 30 seconds of turning the appliance on was just icing on the cake
Lets also not forget that a conductor as listed in Table 310.15(B)(16) in the 90 degee column is rated for that ampacity continuously…and the temperature rating of the column is exactly what the conductors insulation is rated for…continuously. Now, the reason we limit the ampacity to an 80% value is due to the limitations of the terminations to Overcurrent Devices as prescribed by UL for the device. I can load up a conductor at it’s full ampacity for 2 Hours, 59 Minutes and 59 Seconds…and everything is fine. The moment it gets to 3 hours or more…we got a problem.
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.
WOW … :shock: … not many sparkies out there willing to put their license on the line for an FPE panel with known problems. Probably isn’t aware of the issues. Put this link in your reports … www.inspectapedia.com/fpe/fpepanel.htm
Wouldn’t fly here in NY … You cant do an inspection where a relative or business partner has a financial interest. Period … no disclosure provision for that.
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 …
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.
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!
