Reptile & Amphibian Forums

i'm starting a rack for ball pythons using 3" flexwatt and i was wondering which of these two thermostats would be a better choice? i have been reading the information about them on the MG reptiles site and others but i would like to get some other opinions. thanks ahead of time.

Shawn

Both do the same thing, which is ON/OFF control with some adjustment of hysteresis (difference between OFF temp and ON temp.) Both are durable controllers. The Johnson model has a smaller footprint.

I've had Rancos for a good 4 years now with no problems.

Really, you should look at proportional controllers or dimmers for heat tape. ON/OFF control is good for overhead heat or for upper-limit temp cutoff or else for heater control in a very well-insulated system. If the rack is insulated, then ON/OFF control will be great. If not, it is still safe and OK but the relay will be clicking alot and the heat tape temp will be fluctuating a few degrees every minute or so around the setpoint (which isn't necessarily a bad thing, just not optimized.)

Kind of like driving a car where the gas pedal is either down all the way or up all the way with no variation inbetween. For a drive with no stops or turns until the end, this is fine. For a short drive with lots of stops and turns, ON/OFF control of the gas pedal is doable but not optimized for the best control or the most efficient use of gas.

Anyway, enough of my banter. You're OK with ON/OFF control if you want to go that route. Both units are great for that type of control.

and their performance is comparable. The Johnson can be set up for night drop and as far as I know, the Ranco can not. I also use Helix proportional t-stats and prefer them over the on-offs.
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Louis Kirkland
Cornerstone Reptiles

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Louis Kirkland
Cornerstone Reptiles

thanks for your responses. i went with the johnson controls thermostat. markg, in your response you talk about the rack being insulated... what kind of materials do you suggest to help this issue? i haven't started construction yet so i'm open to any ideas.
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Shawn

Some racks have open sides or open backs. I don't consider those insulated.

I actually prefer racks to allow lots of airflow and not be too insulated. But ON/OFF controllers work best in racks that are mostly enclosed and made of an insulating material like wood.

What I mean is, if the rack is enclosed except for the front, and the heater is in the rack, then when the heat tape warms up to the setpoint and then shuts off (i.e. ON/OFF control) it will take some time before the heat in the cage dissipates, this reducing cycling of the heater and the cycling of the cage temp, due to the insulating qualities of wood.

You can insulated the rack with a piece of 1/4" thick hardboard on the outside back of the rack followed by a piece of 1/2" thick styrofoam. You can glue the foam to the hardboard. You don't want styrofoam touching the heater directly. Always have a buffer of some sort, whether it be air or some material that won't burn/melt at 110 deg F temps.

If you want you can sandwich the foam between hardboard and simply lean it up against the rack's back.