What is a Hofer Thermal Shield (HTS), and why do I need to build one?
The facts are undeniable: the best heaters do stick on sometimes; the best canopy fans will fail to turn one day; and the best chillers do fail. If that happens to you, what will happen to your tank? If you are not home all day and do not have a protection device, like the HTS, to cut power to your lights and heaters if the water gets too hot, your tank may suffer a catastrophic crash. The danger is especially high if one runs high-powered lights under a canopy. A reef tank heated to the mid 90s can start a chain reaction of death, eventually destroying much, if not all, of the macroscopic life in the tank, even if the temperature is lowered to normal only hours later. Does that sound unlikely to you? Check online (search the forums on www.reefcentral.com or www.reefs.org) and see how often it happens! It happens with alarming frequency! I invented this device because heat-related tank crashes can hurt anyone and are relatively common, but until this device, the only solutions to protect against them were very expensive, costing hundreds of dollars like the Neptune Systems AquaController™. With this inexpensive device, only costing approximately $40 in online parts as shown above ($30 without GFCI option), heat-related crash will not destroy your tank.How does it work?
The HTS is a plug-in box containing two normal wall outlets, a "sensing" outlet and a full-power outlet. Into the "sensing" outlet, one plugs, into either socket, an unmodified Ebo Jager heater (other brands are not recommended) which is placed in tank water. During normal operation this sensing heater is technically on but only a tiny bit of power is sourced to the heating coils--actually less than 1.5 watts--and not nearly enough to noticeably generate heat. While the sensing heater is "on," a relay inside the HTS will source up to 15 amps (1875 watts) of wall current to a second full-power GFCI outlet (Note: a less expensive non-GFCI outlet is an option). This outlet should power tank lights and heaters. If the Ebo Jager thermostat senses your tank’s temperature rises above the critical temperature set on the Ebo Jager's temperature dial, the HTS relay switches off, turning off heaters and lights or any other device plugged into the full-power outlet. Power is not restored to the full-power outlet until either the tank temperature falls approximately 6°F (varies around +/- 1°F from heater to heater) or one performs a simple reset procedure.Okay, I'm sold. How do I build one?
This page will show you how.