Reptile & Amphibian Forums

I've tried them both, and here are some observations:

First, keep in mind that both of these racks I'm talking about were in the same room that has an ambient temperature of about 77 to 80 degrees year round; in fact they are about 4" apart against interior walls. Both racks were constructed in the same manner, of the same materials, and have a back and sides that fully cover 3 sides of the sterilite tubs, and both are controlled by proportional thermostats (Big Apple Herp Power).

The back-heat rack used a single strip of 11" flexwatt run up the back, about 6 feet total (for a 10-tub rack). The belly heat rack uses ten 12" strips of 11" wide flexwatt (one per shelf) for heat - I prefer a large warm spot vs. using 3" or 4" wide flexwatt for a smaller hotspot.

The back heat rack had to drive the flexwatt hard more often than I cared for; the Raytek temp gun said it was often 124 degrees, and I'd seen temps just over to 130 degrees a few times. The tape was over 100 most of the time just to keep the warm end of the tubs at 92 degrees. The sides and back of this rack were covered with tempered hardboard and were also insulated with 3/4" sheet foam to prevent heat loss. It seemed like any air circulation in the room would cause the heat tape to work very hard to keep the rack's temperature in the proper range (keep in mind only the front of the rack was open - the 16" side of the 41 qt sterilites that measure 34 x 16 x 6).

In contrast, the belly heat rack rarely drives the tape over 94 degrees to keep the warm spot at about 92-94 degrees. Its back and sides are covered with tempered hardboard, but it is not insulated with foam. The tubs sit on 1/4" thick runners so they never directly contact the heat tape because I didn't want the possibility of friction from the tub sliding on the tape wearing through the flexwatt (that could create a potentially dangerous condition or fire hazard). It's more work to wire-up a belly heat rack, but I'm much more comfortable keeping the flexwatt under 100 degrees than I am having it driven at 100 .

Does anyone else have any input on this subject? Which works better for you?
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Astronomy Picture of the Day

Thanks for the observations and measurments. I hope I have not portrayed this issue as a "debate". In reality I really only care about the misuse of belly heat and don't necessarily believe that back heat is always better.

>>The back heat rack had to drive the flexwatt hard more often than I cared for;

This is the most obvious tradeoff. As I've posted previously, the use of a radiant heat blocker between the flexwatt and the back of the rack has a dramatic (positive) effect on this. Essentially, this turns your flexwatt into an inexpensive radiant heat panel that directs radiant rays directly onto the back of the tub.

>>In contrast, the belly heat rack rarely drives the tape over 94 degrees to keep the warm spot at about 92-94 degrees...

This shows you're using belly heat appropriately.

>>The tubs sit on 1/4" thick runners so they never directly contact the heat tape...

This is probably what's allowing your belly heat to work so well.

>>Does anyone else have any input on this subject? Which works better for you?

I will point out that, as far as I can tell, you've only compared surface temperatures inside of your rack. What's more important is air temperatures. Back heat is often better at producing a hot spot that is uniformly warm throughout the airspace and not just a plastic floor that is the appropriate temperature.

I'm guessing your's is still pretty good since you've provided a 1/4" air space.

Also, since you use such a large patch area of belly heat you're probably heating up the water bowl which increases thermal mass (a good thing to heat the air).

One more question, I've already edited out a bunch of your text so I'm sorry if you've already stated this.

Both racks contain the same species of the same size, correct? Substrate, water bowl and water bowl placement are the same?
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Current snakes:

1.1 Gonyosoma oxycephala - (Silver/Yellow)

3.4 Gonyosoma oxycephala - (Green)

2.1 Gonyosoma janseni - (Black)

Hopefully this thread will provide some helpful insights to people building racks and choosing a heating method...

Here are the answers to your questions:

>>Thanks for the observations and measurments. I hope I have not portrayed this issue as a "debate". In reality I really only care about the misuse of belly heat and don't necessarily believe that back heat is always better.

I actually had this drafted before I saw your thread. I wanted feedback from others that have tried both methods.

>>I will point out that, as far as I can tell, you've only compared surface temperatures inside of your rack. What's more important is air temperatures. Back heat is often better at producing a hot spot that is uniformly warm throughout the airspace and not just a plastic floor that is the appropriate temperature. I'm guessing your's is still pretty good since you've provided a 1/4" air space.

Air temps in the tubs are upper 80's in the back of the belly-heat rack, probably because the back of the rack is sealed on those 3 sides. It works well in that respect and gives me a nice gradient.

The back-heat worked too well at heating the entire tub - internally the tub would be about 88 - 90 at the back (94 on the back of the tub's plastic, taken with the Raytek), and about 83 in the front (open) end. Pulling some of the insulating foam off the front of the back-heat rack would probably have helped to lower the temps in the front of the tubs a few degrees for a better gradient.

I'm not sure if I mentioned it, but the shelves in both racks are 3/4" melamine. This might be benefiting the belly-heat rack, as the heat does transfer through the shelf a bit and may be helping ambient temps inside the rear of the tubs of that rack.

>>Also, since you use such a large patch area of belly heat you're probably heating up the water bowl which increases thermal mass (a good thing to heat the air).

My water bowl is in a 4" PVC sleeve with a 16 oz deli cup sitting inside it and usually sits in the middle of the tub (not over the flexwatt). Sometimes the large adult snakes will push it one way or the other, but in general it's somewhere near the middle and probably not a factor.

>>One more question, I've already edited out a bunch of your text so I'm sorry if you've already stated this. Both racks contain the same species of the same size, correct? Substrate, water bowl and water bowl placement are the same?

Yes, both racks are set up exactly the same except for the heating method: Ball pythons of mixed size (one per tub), same water bowl setup, same substrate (usually newspaper, sometimes sani-chips if I'm leaving them alone for a few days), temp probes in the same positions.
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Astronomy Picture of the Day

You had to know I'd reply.

My answer would be that in all cases, belly heat can work great if you use it and control it wisely and use some metal over the heater to dissipate the heat. Back heat can work great if the room is warm to the point of that the animal can be OK with the rack heat turned off (just not while digesting food) or else you insulate the rack and/or put a front on it if room temps are low.

The benefit of backheat: even if the heater is on full by accident (like your controller probe falls out or some other accident) you won't damage the boxes or kill the snakes or start a fire. Belly heat can be disasterous if allowed to run unchecked. The way to help with this issue is to do what Chris suggested earlier: increase the thermal mass. Freedom Breeder does it by running the Flexwatt in a metal sheath. Now, even on FULL, the heat is dissipated a little, making it safer for the animals in the boxes.

A piece of Flexwatt on a shelf with no cover material to spread the heat and no controller can be a bad situation for the snakes.

In summary -

1. If using belly heat, cover it with metal or expanded PVC or other material to increase thermal mass. Use a proportional controller for best results, or a dimmer for good results, or a dimmer plus an ON/OFF controller for better results.

2. If using back heat, use alot of heated area in the back and insulate the rack as best you can, especially the back behind the heater.
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Mark