I use herpstat,helix,ranco and johnsons.
The herpstat and helix are a better choice if you want extreem accuracy with very little fluctuation as they modulate power output to maintain temp. The Johnsons and Rancos use a positive power on/off switch. They are either full on or full off creating minor flucuations which are fine and probably good for our animals and eggs. If you go Ranco, watch the model. If they have a remote sensing bulb failier, they fail to the "closed"(on) position. this is primarily because they are mainly used in refrigeration applications(commercial walk-in cooler/refers). The Johnsons A419 will fail in the "open"(off) position making them a safer option for many applications.
I like the Helix and Herpstats for rack heat and use the cheaper Johnsons for my incubator, travel cooler and room heat. I have a ranco on a well ventilated rack and use it to control the little a/c unit.
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Steve Perry
North Idaho.

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