Do they usually use a cheaper model for the failsafe and the good one as the normal one? So you use the normal Tstat to set the temp to where you want it and you use the other one to set it higher so that if it fails at least it won't go above a certain point?
I have heard of using a rheostat as a failsafe, if the thermostat fails, the rheostat will stop it from going too high.
Originally Posted by kitedemon
Ultra therms are safer than flexwatt generally the temp I get off maxed out flexwatt is 160+ (I stopped it as there is not point in allowing it to continue it is hotter than my animals can handle. The 17 inch flexwatt is lower voltage but it only hits 85-88 which isn't warm enough.
A fail safe is a secondary t-stat that the primary is regulated by.
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Many proportional designs have feed back circuits so if a probe stops working it will shut down the power to that heater rather than on offs where it will try to hit the target temp on a dead probe. They also have circuits that run checks internally and will also shut down if there is an issue found that is not to say they cannot fail they can and do, but it is to say that some of the failures have built in safety.
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