[RE-wrenches] On demand WH

Solar Energy Solutions solarenergysolutions at yahoo.com
Mon Sep 30 15:05:45 PDT 2013


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 <bteitelbaum at aeesolar.com>
To: RE-wrenches <re-wrenches at lists.re-wrenches.org> 
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: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] 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
>
>
_______________________________________________
List sponsored by Home Power magazine

List Address: RE-wrenches at lists.re-wrenches.org

Change email address & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org

List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org

List rules & etiquette:
www.re-wrenches.org/etiquette.htm

Check out participant bios:
www.members.re-wrenches.org

_______________________________________________
List sponsored by Home Power magazine

List Address: RE-wrenches at lists.re-wrenches.org

Change email address & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org

List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org

List rules & etiquette:
www.re-wrenches.org/etiquette.htm

Check out participant bios:
www.members.re-wrenches.org
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org/attachments/20130930/431b0860/attachment-0004.html>


More information about the RE-wrenches mailing list