Mills 12W, how hot do they get?

[zzz]

How safe is it to use Mills MRA-12 wirewound resistors at the top of their power rating (10W-12W continuous dissipation)? I started worrying about this a little too late -- after I got the boards made and even assembled . I did place these resistors as far from each other and the rest of the components as possible, but I still wonder how well are they going to take the effects of self-heating.

Mills Resistors do not provide any sort of derating curves for these things, and they never replied to me when I emailed them that question, but maybe somebody here could answer from their experience.

[fedde]

I would mount them not too close to the board, otherwise the PCB might crack...

Fedde

[zzz]

Originally posted by fedde
I would mount them not too close to the board, otherwise the PCB might crack...

they are about 1cm away from the board. seemed like enough room to prevent exactly that sort of thing.

[fedde]

That's ok. You could measure the temperature. I think the resistors should be able to handle 10-12W continuously. Otherwise, you can try to mount heatsinks on them if there's enough room...

Fedde