Safe Temperature Ranges Of Electrical Components

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Ravenvalor

Ravenvalor

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Piedmont region of NC
Hello,

I just purchased a FLIR ONE PRO LT in order to inspect a 1940s era church that has fuses and the old BX cable. I plan to introduce a load to the various circuits by plugging in one or two 1500-watt space heaters into the receptacles. Could someone please recommend some temperature maximums that I should be looking for at the screw terminations on the receptacles and on the circuit breakers? Is it safe to assume that the plastic breakers are almost opaque to infrared so I cannot depend on an accurate reading by measuring the plastic on parts of the breakers?

Thanks for the help. I appreciate it.
 
Ravenvalor said:
Hello,

I just purchased a FLIR ONE PRO LT in order to inspect a 1940s era church that has fuses and the old BX cable. I plan to introduce a load to the various circuits by plugging in one or two 1500-watt space heaters into the receptacles. Could someone please recommend some temperature maximums that I should be looking for at the screw terminations on the receptacles and on the circuit breakers? Is it safe to assume that the plastic breakers are almost opaque to infrared so I cannot depend on an accurate reading by measuring the plastic on parts of the breakers?

Thanks for the help. I appreciate it.
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If you plug your test load in and take reading pretty much right away, that plastic probably won't be as warm as it is if you let that load run for at least 15 -20 minutes then check it.

At same time something that is in "good condition" will still heat up some with that kind of load on it for long enough time, the trick is knowing how much is acceptable.
 
Ravenvalor said:
Hello,

I just purchased a FLIR ONE PRO LT in order to inspect a 1940s era church that has fuses and the old BX cable. I plan to introduce a load to the various circuits by plugging in one or two 1500-watt space heaters into the receptacles. Could someone please recommend some temperature maximums that I should be looking for at the screw terminations on the receptacles and on the circuit breakers? Is it safe to assume that the plastic breakers are almost opaque to infrared so I cannot depend on an accurate reading by measuring the plastic on parts of the breakers?

Thanks for the help. I appreciate it.
Click to expand...
The black plastic parts have an emissivity of about .95.
that’s about as close to a perfect black body as one can get.
emissivity is the reason you see black tape on some bus bars that are shot with IR frequently.
Don’t worry about the actual temperature. Look at the panel as a whole and you won’t miss a hot spot.
 
Hv&Lv said:
The black plastic parts have an emissivity of about .95.
that’s about as close to a perfect black body as one can get.
emissivity is the reason you see black tape on some bus bars that are shot with IR frequently.
Don’t worry about the actual temperature. Look at the panel as a whole and you won’t miss a hot spot.
Click to expand...
Use a little logic though. If you have minimal loading because the building isn't really in use, yet the AC has been running, breaker(s) for AC will be hotter than everything else but might not be too hot to be a problem.
 
kwired said:
Use a little logic though. If you have minimal loading because the building isn't really in use, yet the AC has been running, breaker(s) for AC will be hotter than everything else but might not be too hot to be a problem.
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Realistically with minimal loading there isn’t a need for thermography..
I have found bad breakers, loose connections, bad bearings on motors, AC/heat loss on buildings..
All kinds of things over the years
I have a FLIR T640 that’s an awesome camera. Heck, it will even light up your leg veins if you adjust temperature scale properly.
 
Hv&Lv said:
Realistically with minimal loading there isn’t a need for thermography..
I have found bad breakers, loose connections, bad bearings on motors, AC/heat loss on buildings..
All kinds of things over the years
I have a FLIR T640 that’s an awesome camera. Heck, it will even light up your leg veins if you adjust temperature scale properly.
Click to expand...
You are probably right, but some want to play with them anyway and need to know what they are looking at means. Even without thermal imaging or even an IR thermometer, I been asked why the AC breaker is so much warmer than the others. It is because it is the only significant load that has been running. Go to someplace with a lot running and you will find many more breakers that have at least some warmth to them.
 
don_resqcapt19 said:
The UL standard for receptacles permits the connection terminal to have a temperature rise of 30°C over ambient
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If I were to go up into the attic and scan the old BX cable directly and perhaps cover the scanned section with black tape do you think I should stick with 30-degreeC over ambient or maybe adjust downward to say 15-degreeC over ambient?
Could I use the 30-degreesC over ambient for the circuit breakers also?

Thanks for the help.
 
kwired said:
You are probably right, but some want to play with them anyway and need to know what they are looking at means. Even without thermal imaging or even an IR thermometer, I been asked why the AC breaker is so much warmer than the others. It is because it is the only significant load that has been running. Go to someplace with a lot running and you will find many more breakers that have at least some warmth to them.
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Couple of examples of not bad panels
962765B0-0819-4283-B61B-A0BDDA40BEB0.jpeg
 

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Ravenvalor said:
If I were to go up into the attic and scan the old BX cable directly and perhaps cover the scanned section with black tape do you think I should stick with 30-degreeC over ambient or maybe adjust downward to say 15-degreeC over ambient?
Could I use the 30-degreesC over ambient for the circuit breakers also?

Thanks for the help.
Click to expand...
Why are you scanning the cable? The splices/terminations are what is going to be a problem.

If the conductor is too hot it is severely overloaded, and likely also has too high overcurrent setting protecting it. That can be discovered with an ammeter.

Tightly bundled cables maybe somewhat an exception for heat buildup though.
 
Ravenvalor said:
If I were to go up into the attic and scan the old BX cable directly and perhaps cover the scanned section with black tape do you think I should stick with 30-degreeC over ambient or maybe adjust downward to say 15-degreeC over ambient?
Could I use the 30-degreesC over ambient for the circuit breakers also?°

Thanks for the help.
Click to expand...
Cables would be based on the temperature limit of the insulation type used in the cable....90°C insulation has a 90°C limit. Breakers are a different UL standard.
All of the UL standards are viewable for free on the UL site. It would be UL489. They use the same free viewing system that the NFPA does and it is not very userfriendly.
 
don_resqcapt19 said:
Cables would be based on the temperature limit of the insulation type used in the cable....90°C insulation has a 90°C limit. Breakers are a different UL standard.
All of the UL standards are viewable for free on the UL site. It would be UL489. They use the same free viewing system that the NFPA does and it is not very userfriendly.
Click to expand...
And if old BX cables very likely are 60C insulation, which is 140F, a temp that many attic spaces might commonly see if there is no thermal insulation between the cable and free air.
 
kwired said:
And if old BX cables very likely are 60C insulation, which is 140F, a temp that many attic spaces might commonly see if there is no thermal insulation between the cable and free air.
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Under those conditions the ampacity of the conductors is zero amps.
 
kwired said:
So they are fine to be there as long as there is no load on them:unsure:
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The "--" in Table 310.15(B)(1) for 60°C conductors in an ambient exceeding 132°F indicates that the conductor has an ampacity of zero because any current will increase the temperature of the conductor.
 
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