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A question for the electricians

I'm going to bring up a dreaded topic...... substrate heating coils... not
to discuss their merits for growing plants, but to determine their safety.

I know next to nothing about electricity, other than that it costs too
much... and that I've got a healthy respect for it around water.

Currently, there are two commercially available systems to provide substrate
heating on the North American market. One, by Hydro Logix circulates heated
water through the substrate and appears to be a commercialization of a
system first described by Earle Hamilton and Phillip Smelt in an article in
AFM - July 1995. I tried a home built version of the Hamilton/Smelt system
and used it for a while but I found that the internal resistance caused by
all of the twists and turns the water was forced to make required the use of
a very powerful pump to move a relatively small amount of water through the
system. But it DID produce a measurable heating gradient within the
substrate of approximately 5 degrees F.

The other system, from AZOO and marketed by m3, is a mains strength flow of
current through a buried cable. This system is NOT UL or CSA certified and I
have been cautioned that it is potentially dangerous. I know that m3
recommends the use of a GFI on the circuit that the heater is plugged into.

I guess my question is - how real is the danger? Aquarium heaters have
household current running through them, and they are encased in fragile
glass tubes. The AZOO substrate heater is sheathed in silicone and buried
under the gravel. Shouldn't that be safer?

Would I be risking life and limb by installing the AZOO substrate heating
system? How would its lack of CSA certification affect my Insurance Policy?


James Purchase