Tuesday, May 16, 2006

Going Tankless

On Friday morning, a piercing scream woke me better than any alarm ever could. I soon discovered that Jen was rudely informed by our plumbing system that our hot water heater had given out and was no longer working. Unfortunately, this was while taking a shower. Not the best way to start the morning.

ThermocoupleI fooled around with the pilot light for awhile trying to relight the burner. The pilot light would catch, but as soon as i released the priming button to turn the burner on, the flame would go out. After work, my stepdad told me that it was likely due to the thermocouple going bad. This little copper safety device ensures the pilot flame is present. When heated by the pilot flame, a small electrical signal is generated and sent to the main gas control valve. In the event of pilot flame failure, the electrical signal is no longer generated, and the main unit shuts off the gas flow to the burner equipment. So when our electrical signal was gone, so was our water heat. Fortunately, this was a fairly easy replacement, and it only cost a whopping 4.95 for a new thermocouple!

So the water heater limps on, and we have hot water again. But the whole event got me thinking about replacing our 14 year old water heater when we redo the rest of the plumbing in the house. I've heard about tankless water heaters for awhile. They've become standard in green building technology. Low water usage, no standby heat loss (you only heat water as you use it, "on-demand", instead of constantly heating a 50 gallon tank of water all the time), and very small space requirements. The technology has been used elsewhere in the world where water is a premium (Europe, Japan), but has only recently caught on in the US.

An excellent overview of how tankless water heaters work is provided on the Takagi website, as well as other providers (Bosch, Rinnai, Paloma). Basically, you never run out of hot water... the tank can always heat water on the fly. The biggest disadvantage is that you need to get a large (read: expensive) tankless heater if you expect to have more than 1 "major application" at a time. This means 2 showers or 1 shower + dishwasher. Most can support 1 shower + a sink. But they last a LONG time, manufactures claim 20+ years. Some people say even longer.

The only other bad thing is the initial cost. It's about twice as much as a traditional tank heater. For a model that provides for 2 major applications, it is about $1000 (they also need special ventilation too). But part of this cost can be offset since because they are about 85% efficient, they qualify for a $300 energy credit for next year's taxes.

All said and done, I think the pros may outweigh the cons. In addition to the cool sustainability points for being green (and saving greenbacks in terms of nat. gas costs), I really like the space efficiency aspects. We'll have to do more investigation on these tankless units. Any feedback or insight is welcome!


Zinny said...

I looked into those tankless heaters last year when my tank whent out. They are great in the long run, but not for those who don't plan on investing years into a house to recover the cost.

Same with solar panels.

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