I bet my setup using quad ranco etc 111000 is safer than a single herpstat or a single helix.
ARS rack, two 6" wide heaters, each on a different dual ranco thermostat. 33" deep tubs.
1 ranco goes hot, the second ranco kicks in and regulates it.
One ranco goes cold, they still have the other heat tape and pair or thermostats.
1 section of heat tape fails, I have the other.
Can it fail? Of course.
Is it safe. In my opinion, yes.
Do I have spares? Yes.

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