[RE-wrenches] On Demand Heaters for SDHW

Fri Sep 17 11:01:20 PDT 2010

Yes , that is my experience with Rinnai, I'm not at all familiar with other brands. 

Technically speaking, I'm not sure where the temp sensor is (I imagine you can get a diagram from the manuf.),
but once the pre-heated water reaches the tank less the tank less shuts off.
Which may result in hot water hitting the tap a little sooner,
but to me the time difference isn't worth burning the fuel.

FYI- It seems that as the water arrives from the solar system and temp increases,
the flame in the tank less regulates down until it just shuts off.

Wayne 

From: solman at legacysolar.com
To: re-wrenches at lists.re-wrenches.org
Date: Fri, 17 Sep 2010 11:12:34 -0500
Subject: Re: [RE-wrenches] On Demand Heaters for SDHW

Message body

Wayne,

Your 
statement that "The unit will turn off automatically once 
input water temp reaches its programed output temp." seems to contradict the 
statement from Bill saying "All tankless, including solar 
compatible (heaters which modulate fire rate based on _inlet temperature_) have 
a minimum fire rate which is well above zero."

Am i missing 
something?

Kris

Legacy Solar
864 Clam Falls Trail
Frederic, WI 
54837
715-653-4295
solman at legacysolar.com
www.legacysolar.com 

  -----Original Message-----
From: 
  re-wrenches-bounces at lists.re-wrenches.org 
  [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Wayne 
  Irwin
Sent: Friday, September 17, 2010 9:40 AM
To: 
  Wrenches
Subject: Re: [RE-wrenches] On Demand Heaters for 
  SDHW

In our off grid home I installed a Rinnai 
  propane tank less to support
the double pump drain-back system and have had 
  no problems. 
The tips that I suggest are: that the tank less be flushed 
  out regularly, 
even when not being used in-order to reduce any sediment. 

If the water is hard, add a softener or at least a micro filter. 
Scale 
  build up can also be a problem. 
If this tank less unit is being used as a 
  back up, turn it off unless needed.
The unit will turn off automatically 
  once input water temp reaches its programed output temp.
However, the 
  initial water flow is cold enough to trigger the unit to fire-up, wasting 

100,000 btu's of fuel for a minute or so.

Wayne Irwin
Director of 
  Engineering
Pure Energy Solar International Inc. 

State Licensed Solar Contractor
License # CVC56695 
Wayne at PureEnergySolar.com 
http://pureenergysolar.com 
352 
  377-6527 Office
352 
  336-3299 Fax

  The content of this 
  message is Pure Energy Solar Confidential. If you are not the intended 
  recipient and have received this message in error, any use or distribution is 
  prohibited. Please notify me immediately by reply e-mail and delete this 
  message from your computer system. Thank 
  you.

> From: 
  solman at legacysolar.com
> To: re-wrenches at lists.re-wrenches.org
> 
  Date: Fri, 17 Sep 2010 09:01:30 -0500
> Subject: Re: [RE-wrenches] On 
  Demand Heaters for SDHW
> 
> It all depends on whether you are 
  talking financial payback or wise energy
> use. The people who use the 
  least amount of hot water are the people who
> will experience the 
  greatest energy use savings. They are a great option
> for weekend 
  cabins since you don't have to remember to turn off the water
> heater 
  when you leave and you don't have to wait for the tank to heat up
> when 
  you return.
> 
> Kris
> 
> Legacy Solar
> 864 
  Clam Falls Trail
> Frederic, WI 54837
> 715-653-4295
> 
  solman at legacysolar.com
> www.legacysolar.com
> -----Original 
  Message-----
> From: re-wrenches-bounces at lists.re-wrenches.org< 
  br>> [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of 
  Todd Cory
> Sent: Thursday, September 16, 2010 1:55 PM
> To: 
  RE-wrenches
> Subject: Re: [RE-wrenches] On Demand Heaters for 
  SDHW
> 
> 
> The payback on a demand heater in energy 
  savings is like 50+ years. A
> traditional tank heater, super insulated 
  has very little loss.
> 
> Todd
> 
> 
> 
> 
  Peter Parrish wrote:
> You’re right, Todd, there is often a space 
  limitation. But overall, the
> tankless approach is more economical, 
  eliminating the need to keep 80 odd
> gallons of water perpetually up to 
  temperature. Remember the solar heated
> water is "make up water" and 
  can contribute to the temperature of the
> traditional water heater only 
  while hot water is being used. So, my guess is
> that 1/2 of the day in 
  a residence the traditional tank is keeping water up
> to temperature 
  for no apparent use.
> 
> - Peter
> 
> Peter T. 
  Parrish, Ph.D., President
> California Solar Engineering, Inc.
> 
  820 Cynthia Ave., Los Angeles, CA 90065
> CA Lic. 854779, NABCEP Cert. 
  031806-26
> peter.parrish at calsolareng.com
> Ph 323-258-8883, 
  Mobile 323-839-6108, Fax 323-258-8885
> 
> 
> 
  ________________________________________
> From: 
  re-wrenches-bounces at lists.re-wrenches.org
> 
  [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Todd 
  Cory
> Sent: Thursday, September 16, 2010 8:17 AM
> To: 
  RE-wrenches
> Subject: Re: [RE-wrenches] On Demand Heaters for 
  SDHW
> 
> 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?
> 
> Todd
> 
> 
> 
> Bill Loesch 
  wrote:
&g t; 
> Kris,
> 
> 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 w orkings 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).
> 

> Your Takagi needs AC power to (in order of decreasing current 
  requirements
> for a generic power vented tankless)
> power the 
  freeze protection heating elements
> run the primary combustion 
  fan
> run the secondary combustion fan
> provide control 
  to
> gas valve
> water valve
> 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.
> 
> Long live the 
  thermocouple.
> 
> My compliments on your simplistic approach to 
  coordinate the solar storag e
> tank and tankless. Simplicity is the 
  ultimate sophistication.
> 
> Bill Loesch
> Solar 1 - Saint 
  Louis Solar
> 
> 
> 
> PS I reiterate, despite other 
  RE-Wrenches list comments to the contrary
> about
> "modulate 
  to
> zero", NONE of ANY of the Big Five tankless manufacturers that 
  market to
> North America have a low fire rate which modulates to zero 
  or anything near
> it for the very same reason that you will never get a 
  trickle of hot water
> out of any tankless water heater. (~0.5 gpm 
  minimum activation flow
> requirement)
> 
> Comparing 
  condensing heaters with ~200,000 max BTU/h input
> Bosch GWH C 800 ES 
  19,900 BTU/h
> Noritz NRC 111 11,000
> Paloma no condensing 
  heaters
> Rinnai RC98HPe 9,500
> Takagi T-H2 13,000
> 

> Thanks for your patience, I hope it was not too techn ical.
> 

> ----- Original Message ----- From: "Peter Parrish"
> 
  <peter.parrish at calsolareng.com>
> To: "'RE-wrenches'" 
  <re-wrenches at lists.re-wrenches.org>
> Sent: Tuesday, September 14, 
  2010 10:37 AM
> Subject: [RE-wrenches] On Demand Heaters for 
  SDHW
> 
> 
> 
> We have a SDHW client that wants to 
  replace his old water heater with
> a new tankless water heater. We do a 
  SDHW system about once a year,
> and only for clients that are getting a 
  PV system from us to begin
> with. So this is not a
> big business 
  line for us and we are behind the curve in terms of
> understanding the 
  latest technologies.
> 
> As I remember from an excellent workshop 
  that I took about four years
> ago: when used in conjunction with a SDWH 
  system, the tankless heater
> should
> 
> (1) Modulate heat 
  input based on INPUT water temperature
> (2) Be able to modula te down 
  to ZERO BTU/hr
> 
> The only unit I knew of back then was the 
  Bosch 125BS (I believe).
> Today I can't find any bigger units that fit 
  the above requirements.
> 
> Short of using two Bosch 125BS units 
  in parallel, does anyone have a
> solution?
> 
> - 
  Peter
> 
> Peter T. Parrish, Ph.D., President
> California 
  Solar Engineering, Inc.
> 820 Cynthia Ave., Los Angeles, CA 
  90065
> CA Lic. 854779, NABCEP Cert. 031806-26 
  peter.parrish at calsolareng.com
> Ph 323-258-8883, Mobile 323-839-6108, 
  Fax 323-258-8885
> 
> 
> 
> 
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> 
> --
> 
> Todd Cory
> KE6SXS
> 
  toddcory at finestplanet.com
> Mt. Shasta Energy Services
> License 
  C-10 #811428
> P.O. Box 689
> Mt. Shasta, CA. 96067
> (530) 
  926-1079
> <!--[if !supportEmptyParas]--> 
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> ∞ Thomas Edison, in conversation with Henry Ford and Harvey 
  Firestone,
> March 1931
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