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Re: Soil Heating Cables
>Has anyone tried or considered using soil heating cables for aquarium
>use? They are used in greenhouses and coldframes for plant propagation
>and are typically buried in soil. Two brands I've looked at, Gro-Quick
>and Redi-Heat, are described as having a tough, moisture proof pvc
>jacket and a continuous safety grounding braid. Cables come in lengths
>of 10 to 240 feet with either automatic pre-set thermostats (70 F), or
>for use with a separate thermostat which costs $142. Since they are
>described as "moisture proof" and are designed for use in wet
>environments, I wonder if they could be used for substrate heating? Any
>thoughts?
I *strongly* reccommend you *not* use these cables *submersed*. With wire,
"moisture resistant" (actually normally "water resistant" printed on the
cable) usually means that the cable is suitable for operation in either
moist enviornments (think high humidity and maybe in a place where the
cable might get dripped on). This is how the famous "orange extension cord"
you can get in a hardware store is classed.
What you need is a "submersible" cable, one rated for continous submersion
in water. I like to use cable that is rated for use with submersible pumps
when I need a submersible cable, something like Carol Super-Vu-Tron III or
Coleman's Seoprene. These cables both have "water resistant" printed on the
cable itself, but if you look it up (and even call the manufacturer as I
did in the Coleman Cable case), you see them listed as suitable for use
with submerisble pumps and rated for continous submersion in water. There
is a big difference here since many plastics do not hold up well over time
when continually under water. Lots of things become brittle and crack over
time, and the cracks than leak... and ... Bzzt!
You might try using one of the mats they sell for seed starters stuck to
the bottom of your tank though.
BTW, someone mentioned using enameled wire for the under gravel heater.
While I doubt the enamel will have a problem under water, even the heavy
nyleze cables aren't all that resitant to abrasion. Messing around in the
substrate will cause the gravel to grind into the enamel and probably
scratch enough of it off to be a problem over time. I think
teflon-insulated wire, especially the 1000 volt EE type (which has a
slightly thicker teflon jacket) is better since the teflon can mush around
a bit rather than just scrape off when abraded. Teflon also holds up VERY
well under water, although you need to keep it away from strong ultraviolet
light.
-Bill
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Waveform Technology
UNIX Systems Administrator