Duplicate post?

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Typically if you are running the same wattage and not exceeding the max wattage of the thermostat you 'can' run them all together.

That being said, you're probe is only on one so you cannot ensure 100% accuracy across all enclosures. I have some PVC enclosure that all run off the same thermostat (3 seperate sections of flexwatt with no problems and +/- 2 difference between them.

If you are going to run it this way plug them all in at the same time and test the temp of each one and see if it will work for your application. Just remember if the temp drops on one pad without the probe and the pad with the probe is still at the right temp you will not be able to recover the lost heat.

Example:
I have 3 PVC enclosures stacked on top of each other. The top two run off the same Herpstat, the heat tape acts the same when the bottom sureface is the PVC. The bottom rack is resting on a wood table and is on a seperate herpstat since the heat tape heats differently when resting on solid wood rather than PVC.