Sad day :/

[BeanAnimal]

Bimetalic what ?

"And today the EHEIM adjustable heater is an ultra-modern electronic thermal device with the best available technology."

Yes - there are some heaters that do not use a bi-metal thermostats and instead typically use an SCR (Silicone Controlled Rectifier) to switch the 120V ac current on and off. The failure mode of an SCR is shorted 99% of the time. I don't care to dismantle an eheim heater to analyze the circuit, but am willing to bet it is far form "ultra-modern" and instead a rather simple thermostat driven SCR.

But - let's assume that it is not an SCR and rather a sophisticated PID with a fail-safe and a IBGT drive or reliable high quality miniature mechanical relay, etc. That would meant that chances of failed closed (heating mode) would not happen.... but we all know that ehiem heaters fail, often ON with the same regularity as any other on-board thermostat heater....

So logic still dictates that we want to use an external temperature controller and if the heater has an on-board thermostat, that it be set a degree or two above the nominal system temperature to act ONLY as a fail-safe.

 

[ReeferFive-0]

This "change them out annually" trend is bothersome... Using a controller would provide infinitely more safety.

I agree with this. In my first comment in the thread I stated many people here use titanium heating elements with controllers too. I currently have a Sicce Scuba heater. I never really considered a controller as a failsafe for this type of heater, but due to this discussion I'm going to get one for redundancy.