[RE-wrenches] tankless hot water and pumping question

[Darryl Thayer]

Hi Todd
the energy for pumping even with this surface tank is to give concern. Set your water resivour precharge low, perhaps 15 to 20 PSI set your cutoff at 20 to 25 PSI be careful the tankless may not run under these condtitons.  I have never seen a pump on demand that did not greatly increase the pump energy, and the below mentioned pump will not work well with a pump-to-demand system as it will constantly cycle.  

My building inspector does not allow grade level tanks as the warm temp adds to baterica growth.  

I think the better choice is a DC pump such as mentioned below, rather than an AC that requires the operation of the inverter.  
Darryl 


--- On Thu, 11/13/08, robert ellison <reellison at gmail.com> wrote:

> From: robert ellison <reellison at gmail.com>
> Subject: Re: [RE-wrenches] tankless hot water and pumping question
> To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
> Date: Thursday, November 13, 2008, 8:28 PM
> Todd,
> I have had good luck with systems like this using a Shurflo
> 120 volt pump
> 3.3 GPM but the 24 volt is simular. If you feed them from a
> standing tank
> they seem to pump well over spec and hang around for a long
> time. Run the
> output to as big a pressure tank as you can get. The larger
> the better, in
> some instances i have used a pair of 80 gallon tanks. Long
> draw time between
> having to rely on just the pumps output.
> 
> The heater you re thinking of is the Aquastar hydro. 120HX
> I think. Works
> well with the above combination just feed it with 3/4 water
> lines in and out
> and put at least 6' of flue pipe on it. Make sure you
> oversize the gas line
> also.
> 
> Later,
> Bob
> 
> On Thu, Nov 13, 2008 at 8:58 PM, Todd Cory
> <toddcory at finestplanet.com>wrote:
> 
> > 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*
> >
> > * *
> >
> > "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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