How do "over heating" failures occur?

[DLLNP]

Hello!

We have all seen (or maybe experienced?) the horror stories of a thermostat failing, resulting in an animal being burned or killed.

My question is: How does that happen?

I think (as far as I know, correct me if I am wrong) most heat mats and/or heat tape if left unregulated are not normally capable of heating up enough to seriously hurt or kill your animal when functioning properly.

Let me be clear about what I mean... an unregulated heat mat normally won't reach temperatures above 120°F or so, of course this is way above what your husbandry requires but it's not going to melt plastic, burn scales or start a fire. (again... I am not at all suggesting not to use a thermostat, and I know 120°F is not a safe temperature for most animals but it is far from a temperature that will cause immediate serious damage which I imagine must be in the +150°F?)

So when a thermostat fails... I don't understand how the extreme over heating occurs (burns, death)?

OR is it that the heat mat fails, burns out the thermostat probe and then the temperatures can skyrocket? In other words, is over heating more of a faulty heat mat issue rather than a faulty thermostat?

I am curious to know you experience and thoughts?

[TRD]

By using too powerful heating elements in the first place. You should always pick the right wattage for the job, ideally you want your heating element to run as close as possible to 100% power. If it runs at 30-40% and reaching ideal temperatures, if the stat fails for whatever reason (probe movement/blockage/failure on the stats own fail-safe, etc) and it goes 100%, you'll cook your animal.

Many people are using 150W CHE and whatnot while they really should be using 50W in the space they have.

Many reptiles are fine to survive a while on much colder temperatures than they should be kept at, however they may perish quickly when kept at much higher. I never understood why some people choose to keep so much overhead in their heating that they will never use.

[Jim Smith]

It's usually when the heat mat fails or shorts out causing it to overheat to the point of melting the pad and sometimes even starting to melt plastic/PVC cages. If you have a reliable thermostat, the probe should detect the excessively high temperature and shut off the power to the heat mat. It's when you have a dual failure of the heat mat and the thermostat probe probe when the real danger occurs. I switched over using Radiant Heat Panels and even with no thermostat (which I would never do), there is much less of a chance of an equipment failure resulting in overheating.

[Herpin' Man]

It can also occur when a probe comes loose. It will register a cooler temperature, causing the heat tape or mat to run full time.

[pet_snake_78]

Ive had a hydrofarm stick in the on position before. Each rack now has 2 tstats. The primary is a herpstat. They are set with a low temperature alert a couple of degrees above room temperature so that if it is dislodged it will cut off. The herpstat is then plugged into a cheap tstat like a hydrofarm/Zilla/Etc which its probe is attached to a different level in the rack and it is set much higher than the day temp of the herpstat such that it is constantly on unless the heat tape gets 10F above target which would indicate something has gone wrong. It's amazing to me that people will have hundreds of dollars in live animals that they spent years raising up to breeding size but they won't spent a couple hundred bucks per rack to protect their investment/animals. Let's say you have a 10 slot rack, the two tstats are costing only 20$ per slot, not much when you think about it.