A quick google search turns up two different hits as to the maximum temperature these top out at.
One source reports 140 degree F and another 160 degree F. That's the upper limit.
One search result describe the trace cables as 'low-temperature self-limiting devices'
What you have to understand is that the temperature regulation in these devices is designed to work while keeping the manufacturing cost as low as possible (i.e. cheap).
So just because the regulation turns off, it doesn't mean it turns off at a temperature that's healthy for optical equipment.
Heating up a copper pipe more than necesary... adds a margin of safety that ensures the pipe won't freeze.
Maybe the cable will run at a lower temperature - you can test it out with a temperature probe to verify.
But you'll want to do so across various temperatures to simulate changes to the outside temperature and for an extended period (think 8 hours minimum, over several nights).
Since it is working well for Jii, possibly he has already done this type of testing and would be willing to share his data on it?
Or maybe he has a unique approach that doesn't use the integrated temperature controllers most of these come with.
It's a novel thought, but given some of the reasonably cost-effective dew heater options already available on the market, I would recommend sticking with one of those instead.
Will it work - probably. Will it work well - likely not, at least not without some effort and customization.
As always YMMV.
Edited by John O'Grady, 25 March 2020 - 11:24 AM.