Hi Bill, et al,
There are two major categories of tankless water heaters-natural draft
(which work very similar in control aspect to a conventional tank i.e..
no electric required, some form of pilot light) and power vented (all
power vented machines have need for at least a fan, most a computer with
some form of display included - if your own body is incapable of telling
you if the water is sufficiently hot).
Of the Big Five (major players in the tankless market) all manufacture
one or more models of power vented tankless. Today, only Bosch markets a
natural draft tankless. Bosch offers more than one model of natural
draft tankless, standing pilot and intermittent pilot. If you like
simple, trouble free, and low life cycle cost, you have but one choice.
http://www.bosch-climate.us/files/201304181918370.520PN_English_06.2011.pdf
What must be properly addressed with _any_ tankless is intake and
exhaust venting, gas line sizing, and water quality. Since this isn't a
tank, the pilot flame does almost nothing in terms of freeze prevention.
Some manufacturers state flow rate for their heaters without also
providing temp rise. Flow rate without temp rise is meaningless. The
above is a 117,000 BTU/h machine. Sometimes winter ground water
temperatures are significantly colder than summertime temps. If you want
hot water in the winter, too, make sure you use the appropriate temp
rise. Hardness is the biggest issue with water quality, if you scale the
heat exchanger you won't get the performance advertised. If you have
hard water, a water softener or descaling _as required_ is necessary.
I am a big fan of tankless and have been since '89 when I was first
introduced to them as a user. Today, I install and troubleshoot all five
major manufacturers. Co-located with the load, tankless provides you not
only endless hot water but also instant hot water.
Good luck,
Bill Loesch
Solar 1 - Saint Louis Solar
314 631 1094
On Sat, Sep 28, 2013 at 10:19 PM, frenergy wrote:
Off-grid Wrenches,
I'm working on a load sheet and am having a hard time finding
standby and while firing electrical usage for a propane-fired on
demand water heater. Do they some/all have standing pilots, glow
bars, something else? I'm guessing the standby power needs are very
low but we all know how even 10-15 watts adds up over 24 hrs when
you're off-grid.
If any body has some actual numbers rather than just pdf.specs
(though manus specs might help some), I would be most grateful.
Thanks in advance.
Bill
Feather River Solar Electric
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