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<font size="+1"><font face="Arial"><small>I know this was not the
question, but this whole thread is predicated on the use of a demand
hot water heater. Unless there is a space limitation, why would this be
done over a traditional tank unit?<br>
<br>
Todd<br>
<br>
<br>
</small></font></font><br>
Bill Loesch wrote:
<blockquote cite="mid003001cb5591$47b08240$6401a8c0@HP3MHz" type="cite"><br>
Kris,
<br>
<br>
Boiler manufacturers today get starry-eyed when their machines are able
to provide a 10:1 turndown ratio. Even the venerable natural draft
Bosch 125BS * provided a better than 4:1 turndown ratio and all the
condensing powervent units compared below regularly offer 10:1 and some
better than 20:1. With each benefit comes a disadvantage, like with
current production cars, serious repair/maintenance takes place
primarily at the dealer since they are usually the only ones to pony up
for the multitude of specialized test equipment. I find it a bit of
backward progress to have to tell someone that the reason they don't
have reliable hot water is because they don't have the current software
update (due in no small part to the marketing gurus who have no qualms
about using the customer as the proving grounds for their product).
Many plumbers have no clue to the workings of a combustion analyzer, a
necessary tool for negative pressure gas valve tuning and replacement
(and a multitude of other tasks where the blue flame is no longer
sufficient to be able to deliver optimum performance).
<br>
<br>
Your Takagi needs AC power to (in order of decreasing current
requirements for a generic power vented tankless)
<br>
power the freeze protection heating elements
<br>
run the primary combustion fan
<br>
run the secondary combustion fan
<br>
provide control to
<br>
gas valve
<br>
water valve
<br>
control board (oftentimes with digital display) which provides
the logic and timing circuits for the multitude of sensors and limit
switches and remote controls and wireless remote controls etc., etc.
<br>
<br>
Long live the thermocouple.
<br>
<br>
My compliments on your simplistic approach to coordinate the solar
storage tank and tankless. Simplicity is the ultimate sophistication.
<br>
<br>
Bill Loesch
<br>
Solar 1 - Saint Louis Solar
<br>
<blockquote type="cite"><br>
<br>
PS I reiterate, despite other RE-Wrenches list comments to the contrary
<br>
about
<br>
"modulate to
<br>
zero", NONE of ANY of the Big Five tankless manufacturers that market
to
<br>
North America have a low fire rate which modulates to zero or anything
near
<br>
it for the very same reason that you will never get a trickle of hot
water
<br>
out of any tankless water heater. (~0.5 gpm minimum activation flow
<br>
requirement)
<br>
<br>
Comparing condensing heaters with ~200,000 max BTU/h input
<br>
Bosch GWH C 800 ES 19,900 BTU/h
<br>
Noritz NRC 111 11,000
<br>
Paloma no condensing heaters
<br>
Rinnai RC98HPe 9,500
<br>
Takagi T-H2 13,000
<br>
<br>
Thanks for your patience, I hope it was not too technical.
<br>
<br>
----- Original Message ----- From: "Peter Parrish"
<a class="moz-txt-link-rfc2396E" href="mailto:peter.parrish@calsolareng.com"><peter.parrish@calsolareng.com></a>
<br>
To: "'RE-wrenches'" <a class="moz-txt-link-rfc2396E" href="mailto:re-wrenches@lists.re-wrenches.org"><re-wrenches@lists.re-wrenches.org></a>
<br>
Sent: Tuesday, September 14, 2010 10:37 AM
<br>
Subject: [RE-wrenches] On Demand Heaters for SDHW
<br>
<br>
<br>
<blockquote type="cite">We have a SDHW client that wants to replace
his old water heater with
<br>
a new tankless water heater. We do a SDHW system about once a year,
<br>
and only for clients that are getting a PV system from us to begin
<br>
with. So this is not a
<br>
big business line for us and we are behind the curve in terms of
<br>
understanding the latest technologies.
<br>
<br>
As I remember from an excellent workshop that I took about four years
<br>
ago: when used in conjunction with a SDWH system, the tankless heater
<br>
should
<br>
<br>
(1) Modulate heat input based on INPUT water temperature
<br>
(2) Be able to modulate down to ZERO BTU/hr
<br>
<br>
The only unit I knew of back then was the Bosch 125BS (I believe).
<br>
Today I can't find any bigger units that fit the above requirements.
<br>
<br>
Short of using two Bosch 125BS units in parallel, does anyone have a
<br>
solution?
<br>
<br>
- Peter
<br>
<br>
Peter T. Parrish, Ph.D., President
<br>
California Solar Engineering, Inc.
<br>
820 Cynthia Ave., Los Angeles, CA 90065
<br>
CA Lic. 854779, NABCEP Cert. 031806-26 <a class="moz-txt-link-abbreviated" href="mailto:peter.parrish@calsolareng.com">peter.parrish@calsolareng.com</a>
<br>
Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885
<br>
<br>
<br>
<br>
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<h2><span style="font-size: 9pt;">Todd Cory<o:p></o:p></span></h2>
<h2><span style="font-size: 9pt;">KE6SXS<o:p></o:p></span></h2>
<p class="MsoNormal" style=""><b><span
style="font-size: 9pt; font-family: "Comic Sans MS"; color: rgb(0, 116, 0);"><a
href="mailto:toddcory@finestplanet.com"><span
style="font-family: "Times New Roman"; font-weight: normal;">toddcory@finestplanet.com</span></a><o:p></o:p></span></b></p>
<h2><span style="font-size: 9pt;">Mt. Shasta Energy
Services<o:p></o:p></span></h2>
<h1><span style="font-size: 9pt; color: rgb(0, 116, 0);">License
C-10<span style=""> </span>#811428<o:p></o:p></span></h1>
<h1><span style="font-size: 9pt; color: rgb(0, 116, 0);">P.O.
Box 689<o:p></o:p></span></h1>
<h1><span style="font-size: 9pt; color: rgb(0, 116, 0);">Mt.
Shasta, CA. 96067<o:p></o:p></span></h1>
<p class="MsoNormal" style=""><b><span
style="font-size: 9pt; font-family: "Comic Sans MS"; color: rgb(0, 116, 0);">(530)
926-1079<o:p></o:p></span></b></p>
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<pre><span
style="font-size: 8pt; font-family: "Comic Sans MS"; color: rgb(153, 51, 0);">“I'd put my money on solar energy...I hope we don't have to wait till oil and coal run out before we tackle that." <o:p></o:p></span></pre>
<p class="MsoNormal" style=""><span
style="font-size: 8pt; font-family: "Comic Sans MS"; color: rgb(153, 51, 0);">∞
Thomas Edison, in conversation with Henry Ford and Harvey Firestone,
March 1931</span><b><span
style="font-size: 9pt; font-family: "Comic Sans MS"; color: rgb(0, 116, 0);"><o:p></o:p></span></b></p>
<p class="MsoNormal" style=""><span
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