Reptile & Amphibian Forums

"Back heat: Tends to be a bit better at creating warm zones and is less susceptible to probe placement errors. But the flexwatt does need to run hotter the way it's typically setup. Much of this can be overcome with the use of an air space and foil-faced insulation.

If you use back heat take advantage of air spaces and reflective insulation. And still provide thermal mass."

I plan on doing a rack this weekend with back heat. So what does all that mean? Air space...between? The tape and back wall? Hows do I provide thermal mass? I don't even know what thermal mass is? The amount of space inside the tub that is heated? I thought I had a good handle on what I planned to do until I read this post from down below.

Thermal mass is hard to explain but easy to understand. At least for me - maybe somebody else can explain it better.

Basically radiant heat heats objects, not air. Those objects in turn become secondary radiators of heat. Perhaps think of them as increasing the surface are of heat.

A recent poster mentioned their experience with thermal mass. The placed a clay flower pot for a hide over or under (can't remember) a heat source and found the cool side of their cage was suddently 8* higher. Why? Because of the increase in thermal mass. The flower pot heated up and helped distribute the heat around the cage.

Thermal mass can be increased both inside and outside of the rack tubs. The easier way to do it inside is to use hides and water bowls made from objects with good thermal mass. Heavy ceramic bowls and flower pots are good examples.

For the outside, a 1/4" thick layer of expanded PVC between the heat source and tub is a good idea, at least for belly heat.

Regarding the reflective insulation and the air space, I'm not completely comfortable getting into that and making recommendations. Just understand that some reflective insulations need to be treated carefully in regard to fire hazzards and that if they're sandwiched without an air space they no longer reflect the radiant energy.

This is a confusing subject. There's lots to learn online if you care to do several google searches.
-----
Current snakes:

0.2 Gonyosoma oxycephala - (Silver/Yellow)

3.3 Gonyosoma oxycephala - (Green)

2.1 Gonyosoma janseni - (Black)

3.3 Gonyosoma janseni - (Black & Tan)

The heat tape emits radiant energy, as it hits "thermal mass" (anything that conducts heat well) the radiant energy is converted into thermal (heat) energy. The "thermal mass" (usually a ceramic dish or flower pot hide) then conducts the heat into the air and surrounding areas.

I don't know if that helped or not, if you are familiar with the scientific forms of energy it might help.
-----
December 9, 2004
Always Remembered
WE REMEMBER YOU GARY!

If I'm using back heat, wouldn't the tub itself heat up and distribute the heat? Granted it's not as good of a heat conductor as ceramic, but still. It's only about a 2" gap. So maybe I have to have the heat tape at 90* to reach an 87* warm side. Wouldn't the water bowls and such just make it more efficient?

>>If I'm using back heat, wouldn't the tub itself heat up and distribute the heat? Granted it's not as good of a heat conductor as ceramic, but still.

Not as good as a conductor but it also weighs a lot less. Furthermore with back heat there is often less surface area of tape exposed to the boxes and it's also farther away from the boxes.

>>It's only about a 2" gap. So maybe I have to have the heat tape at 90* to reach an 87* warm side. Wouldn't the water bowls and such just make it more efficient?

I don't know if more efficient is how I think about this. Perhaps more effective as the heat is better distributed around the cage. Waterbowls are a great source of thermal mass as water itself has excellent TM. Ceramic water bowls are better than plastic. But they are typically kept at the cool ends of cages so other sources of thermal mass are nice to have.

BTW, the snakes themselves are often the biggest contributor to TM in rack setups. This holds most true with Ball Pythons that are so heavy relative to their length. This is why a heating setup that works for Ball Python keepers may not be appropriate for somebody keep Racers.

I'm not comfortable with an animal being the greatest contributor to TM in a cage but I realize this is hard to avoid with BP's.
-----
Current snakes:

0.2 Gonyosoma oxycephala - (Silver/Yellow)

3.3 Gonyosoma oxycephala - (Green)

2.1 Gonyosoma janseni - (Black)

3.3 Gonyosoma janseni - (Black & Tan)

I'm gonna run the rack without the snakes for a few days anyway, so I'll have time to tweek it. Given what I've figured out here along with what I learn doing the research in the meantime I'm sure I can get it to work. Thanks guys.