I've used Sunbeam heat pads. The type with the 3 position switch.
They are relatively safe if used on the low setting, but they discolor over the years, and I have some old ones that have big black spots at the points of contact where the heat was the highest. They will eventually become brittle and the plastic sheathing will break open exposing the internals.
Its not the best to put them under heavy cages. I would recommend a spacer to jack the cage up and prevent the heat pad from having the direct weight of the cage or tank on it.
They can also be used with standard light dimmers to turn them down.
They are built with internal bimetal overtemp t-stats, so there is some provision for them limiting their own output, and this is a CSA requirement.
Personally I like and use Flexwatt heat tape, which is now being made by Calorique. It distributes the heat across a wide area, greatly reducing hot spots thus it is less of a fire hazard, than light bulbs and almost all other heat sources. It can also be cut to any length and the watts per foot is consistent no matter how long or short they are made. The product lasts virtually forever and doesn't burn out.
The drawback is that it's not a "consumer ready" product , and as illustrated above requires wiring which creates somewhat of a problem and potential hazard for those not qualified to do such.
The product is also not CSA approved, but there are various reasons for this. To start with , last time I checked it hadn't been officially submitted because there is no Canadian standard for carbon film heaters.
(This was the info given to me from the factory a couple years back)
The orignial company Flexwatt Inc. was driven to bankruptcy
a few years back, partially the result of law suits in Canada for fires alledged by them to be caused by incorrectly installed ceiling panel heaters.
The ceiling heaters are a different product, than the heat tape but once bitten twice shy.
I don't imagine there is much insentive now to even try to market their product in a country where there were prior litigations.
They wont ship it up here, but herp supply wholesalers will.
You use it at your own risk
I think it's worth mentioning that Flexwatt heat tape is not originally a Herp product.
The stuff is made to heat ceramic flooring, and is normally placed under floor surfaces in hallways bath, and steam rooms.
Our use for it is secondary.
The way the product works is that carbon particles(graphite) is spread across a sheet of plastic in a thin continuous film.
This film is conductive, and when voltage is applied via the side conductors, current flows across the film, from one side to the other , and this produces heat as a result.
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