All,
We are finding, with rare exception, that despite claims by On Demand
manufactures of their units being, "solar compatible" most do not reach the
common sense definition of being so. I would suggest anyone installing a solar
preheat tank before an on demand talk to no less than two people from the
manufacture to confirm the nature of the solar compatibility and get a plumbing
diagram from them as well. We like the Takagi as it seems to be truly solar
compatible. Many of our clients have light switches installed to facilitate
easily turning the unit on or off so in the summer they can get rid of needless
short cycling or any phantom load. But, honestly, for conventional homes we
have moved away from advocating for on demands thinking standby heat loss for
an occupied homes is so little that the expense of the 'maybe energy saving
device', by and large does not warrant its use in these situations.
Thanks,
Andrew Koyaanisqatsi
President
Solar Energy Solutions, Inc.
Since 1987,
Moving Portland and Beyond
to an Environmentally Sustainable Future.
503-238-4502
http://www.solarenergyoregon.com/
"Better one's House too little one day
than too big all the Year after."
________________________________
From: Brian Teitelbaum <[email protected]>
To: RE-wrenches <[email protected]>
Sent: Monday, September 30, 2013 9:39 AM
Subject: Re: [RE-wrenches] On demand WH
Hi Bill,
I'm still running an Aquastar 125BS (original French model, before Bosch bought
them) that I installed in 1990. I've had to rebuild the water valve once (after
a freeze up; it's in an unheated outside closet on the north side of my house),
the high-temp sensor once, and I needed to replace the thermocouple a few times
when I was just using a small propane tank to run it. I installed a 250 gallon
propane tank in the late nineties and haven't had to replace the thermocouple
since.
The Aquastar still works great, even when my incoming water temp is near
freezing. I just have to use less cold-water mix during the winter.
Are you finding the new Bosch models to be this reliable?
Brian Teitelbaum
AEE Solar
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Bill Loesch
Sent: Monday, September 30, 2013 5:00 AM
To: RE-wrenches
Subject: Re: [RE-wrenches] On demand WH
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
>
> ------------------------------
>
> _______________________________________________
> List sponsored by Home Power magazine
>
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