Hey Carole,
I'll try to answer your question as best I could. For starters, under belly heat, IMO, does not give the herps much latitude should a system fail, and unfortunately, as we have seen many times, snakes will lie on hot surfaces with nary a budge when such systems fail or go haywire. Yes, it is true that heat panels can go bad, but the units, at least that I have used and have been using for several years, have all been nothing short of dependable and along with the Helix thermostats, have provided my bloods and short-tails with a comfortable and hospitable ambience. In other words, this S..., works better than anything out on the market. I use Flexwatt heat tape in the rack systems, for juvies and hatchlings, and mid sized adults too, and that also works if put on a thermostat and mounted from the sides, rear of the enclosure or bottom if used with a dado'd channel.
Heat panels differ much in their design and construction from Flex-watt, and other UH devices in various ways and can cost 4-6 times more money, but the quality of the heat and the safety factor involved with the use of this product far outways the cost in my book. Technically speaking, there are several factors that make this product a far better choice than Flexwatt or heat tape, or any other device, and for that you should contact ProProduct personally and speak to Bob. He has always been more than helpful and willing to get to the nitty-gritty of the component parts. I hope that this makes some kind of sense and helps in answering your question.
Also, in answer to someones point about humidity, there is no problem with humidity with this product as this product does not dry the air out, as does the ceramic heatesr. Most times, my cage glass has some mist or dew from the humidity that builds up during the day. I have several vents installed on my cages and with that, they still provide more than adequate humidity. I also, never have a problem with bad or stuck sheds or even, dimpling,
-Angel
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"Until we lose our self, there is no way of finding our self."
-Henry Miller.