At SPI last year there was at least one company offering this, and
there's another company from Tallahassee also looking into it:
www.usa-eds.com
I'm not an expert by any means but I think that even 120F doesn't kill
legionella-- you need to get to 140F. And even if you do 140F, I imagine
you could still have it in the bottom of the tank (if it's electric).
A few years ago, a Solar Decathlon team used some kind of ionization to
combat it, I believe using something intended for hospitals.
DKC
On 2013/5/14 8:39, Steven Lawrence wrote:
Luke,
Most tankless hot water heaters can't accept pre-heated water. Some of
them can, but even still these have a minimum heat input into the
water. You may run into a situation where you have 105F water into the
tankless and the thing won't fire up due to safety reasons (can't put
out 130F or something similar like that). And the issue with 105F is
you start exposing yourself to the potential of getting Legionnaires'
disease.
-Steven
Hi Wrenches,
Now that the cost of modules has come down so much, has anyone out
there experimented with solar electric water heating? As in: direct
connecting a short series string of PV modules to a tank -style
electric water heater with an element of an appropriate voltage and
wattage rating??
A off-grid customer of mine who is also an electrical engineer has a
situation that seems ideal for trying this idea out: he has a
gas-fired tankless water heater and a water source that is very cold
year-round. The idea is to take a 30 or 40 gal electric tank heater,
switch out one of the the 240V elements to something like a 96VDC,
1000W element (difficult to find, but available), and direct connect
3 or 4 60-cell modules in series (with a disconnect and high-limit
control of course). The tank would then serve to preheat the cold
feed to the tankless heater. We think we can get a decent daily
temperature rise with this setup. Probably not enough to heat the
tank to a normal DHW temperature, but certainly enough to offset a
good deal of propane consumption, and all for what I predict will be
considerably less cost than a small solar thermal system.
Has anyone tried this? I'd appreciate any insights or opinions.
Thanks
-Luke Christy
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