Once the lid is put on, a single 3500W electric heating element extends down the center of the coil to heat the tank water. We also purchased a heat pump retrofit kit (www.airgenerate.com), which will be installed in the spring so that we can heat the water more efficiently and use the exhaust air for home cooling...more on that later. Since the tank is not pressurized, I can also modify it to accept solar heated water when we get to that phase in the future. We paid $350 for the heater- a little more than buying a conventional tanked electric heater, but a great price for the benefits of this design.
Thursday, January 15, 2009
Reinventing the wheel is sometimes a good thing- like with tanked hot water heaters. I am not a fan of tankless water heaters (they are either terribly inefficient or prohibitively expensive) and I wanted to have a storage tank so that we could add solar-heated water as a future project. However, traditional tanked water heaters are usually poorly insulated and have a limited lifespan (I hate seeing the pile of hot water heaters at our local landfill). There are some well-built models on the market, but they are crazy expensive. Then I found the HH20 water heater (www.howardharrisbuilders.com) and just installed ours this week. While it looks like the same old tanked water heater, it actually uses a heater exchanger (the finned copper coil) to transfer heat from the tank to the plumbing. Since this design keeps the water in the tank separated from the water you actually use, the tank is not pressurized and (in theory) should never burst or leak. So the unit can be built inexpensively using a plastic tank and 2.5" thick insulated walls- very efficient and very durable.