[RE-wrenches] On Demand Heaters for SDHW

Kristopher Schmid solman at legacysolar.com
Tue Sep 14 09:18:59 PDT 2010


Try the Takagi.  I believe that all their units will modulate down to zero.
Keep on eye on the temp rating of the unit...it is common practice to put
the thermostatic mixing valve on the input side of the tankless.

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 Peter
Parrish
Sent: Tuesday, September 14, 2010 10:37 AM
To: 'RE-wrenches'
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 modulate 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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