[RE-wrenches] tankless hot water and pumping question

Bill Loesch solar1online at charter.net
Fri Nov 14 05:00:19 PST 2008


Todd Cory
Hi Todd,

Congrats on the off-grid solar application to improve quality of life.

I will defer to my more learned colleagues re the optimum water pressure pump.

If you don't want to use any electricity to create the hot water, then you want to use a natural draft tankless. (Like a conventional tank, no electricity required.) Please be aware of the minimum flow requirements to turn on the tankless - something on the order of a half gallon per minute. Less flow than that and the tankless will not fire. If you can find any, the (out of production) piloted Paloma PH series (some folks have said it resembles R2D2) would work on much lower water pressure than the Bosch series which work reliably only with a minimum of 30 psi (e.g. the lower limit of your pump switch would be set to 31 psi or more).

The hydro generated Bosch model sounds great in principle and were able to provide you a tax credit in the previous tax credit program . What is required for the hydro generated models to work (in addition to the hydro generator) is an expensive electronics box and a multitude of connectors which IMHO are not up to the rigors that the piloted models offer, especially in less than pristine environments. The piloted models utilize a thermocouple which most everyone is familiar with and has many fewer connectors. Most all the natural draft piloted tankless machines incorporate a piezo igniter like on your BBQ grill, so turning off the pilot manually and relighting as required is nowhere near the contortionist effort experienced with a tank and provides the savings of no pilot gas usage when not working.

Good luck,

Bill Loesch
Solar 1 - Saint Louis Solar

  ----- Original Message ----- 
  From: Todd Cory 
  To: re-wrenches at lists.re-wrenches.org 
  Sent: Thursday, November 13, 2008 7:58 PM
  Subject: [RE-wrenches] tankless hot water and pumping question


  I am working on a semi-volunteer job for a local non-profit. It is off grid with water being trucked in and stored in a ground level polyethylene tank. 

  I need recommendations for:

  1) A 24 volt DC pressure pump. This is a single residence so can be relatively low volume as it will only feed a shower or sink... no irrigation.

  as well as 

  2) Which tankless (propane) hot water heater would be best? I think there is one that uses the water flow to spin a tiny generator that ignites the burner. Being off grid it is important to not have a unit that draws power 24/7.

  Thanks,

  Todd

  -- 

  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

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“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." ∞ Thomas Edison, in conversation with Henry Ford and Harvey Firestone, March 1931

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