The H.H2O Water Heater: Has Anyone Tried It?

I recently saw an add for this "novel" new tank style water heater. It seems like a good idea with it's plastic, non-pressurized tank. But I have my doubts as to the claims of it's heat capacity. I would like to know if anyone out there has one (or similar) and what they think of it. The link to the manufacturers website is: www.howardharrisbuilders.com/HH20.htm. Thanks in advance for any info.
Dan Akers
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D. Akers wrote:

Some of its claims border on violating laws of thermodynamics. Currently produced conventional electric water heaters have efficiency ratings of 93 to 95 percent based on using 64 gallons of hot water a day, so there's not much room left to gain efficiency with electric heating, is there?
Some of the claims sound like oompah to me. Their unit's "average yearly cost as low as $197.00" compared to a standard unit's "Average yearly cost up to $429.00" without mentioning the total quantities of hot water used during the year.
There do seem to be some attractive features, particularly if that finned copper heat exchanger lasts a lot longer than the the 5-7 years a steel heater tanks lasts around where I live.
But if the heat exchange does spring a leak, I don't what keeps that leak from ending up on the floor.
It seems to be a cross between a conventional water heater and a true demand electric water heater.
I wouldn't write it off completely, but I'd sure like to know how long the consequtive hot showers SWMBO and I could take using our 5 GPM high flow shower head would be.
Jeff
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Jeffry Wisnia
(W1BSV + Brass Rat \'57 EE)
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The primary source of inefficiency of any tank water heater is the fact that some of the heat you put into the water is lost through the sides of the tank before the water is used. Obviously insulation is the primary means to combat that loss.
If one could heat only the water one uses, the standby losses could be eliminated. In many households, you would need to get a tankless heater with enough capacity to heat your coldest water (middle of winter) to the temp you want. This results in a WH with more BTU than you need for much of the year. If one could preheat that water so the tankless dosent need to work so hard and the tank has a lower temp thereby reducing heat loss through the sides (by virtue of a smaller delta T) this would be the best of both systems.
It is reasonable that the efficiencies of both methods could be optimized to obtain a system of overall higher efficiency than either system alone. At least in concept.
This product isn't exactly a combination of a conventional tankless because the primary water is not directly heated by the heat source but instead a buffer volume of water is heated and the heat is transferred to the supply with a heat exchanger. It would still be subject to heat loss through the sides and could still be depleated of heat if you ran the water too long but the prpensity for running out of hot water and waiting seems to be reduced.
If you're into electronics, it sounds similar in concepot to putting an RC filter on the output of a power supply to reduce ripple.
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D. Akers wrote:

It seems to be 173% efficient according to the yellow highlighted text:
"this water heater will heat 10 gallons of incoming 58 cold water to 129 hot water temperature per kilowatt of energy"
10 gallons of water is 80.34lbs and it takes 5,921 BTU to raise the temperature 71F. One kw/h=3,414 BTU
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