[RE-wrenches] SWH - mixing valves

[Bill Loesch]

Hi Kelly,

Is water quality an issue in that location?

More than one tankless manufacturer lists max levels of all or some of the
following:

pH - 6.5 - 8.5
TDS (Total Disolved Solids) - 500 ppm
Total hardness - 6 grains
Aluminium - 2.0 ppm
Chlorides -250 ppm
Copper - 10 ppm
Iron - 0.3 ppm
Manganese - 0.05 ppm
Zinc - 0.5 ppm

as qualifying for the addition of a water conditioner or softener.

In my experience, many folks, even with conditioning/softening equipment
installed (oftentimes inop), are blissfully ignorant of the effects of
water quality until something stops the hot water.

I personally like Bob-O's approach of a warning label at the hot faucet for
solar applications. The code officials in my neck of the woods do not share
my enthusiasm for this approach.

Because here in STL, we additionally have a chloramine presence in the water
this adds a requirement for specialty o-rings, etc. for control items in the
water path.

Hope this helps,

Bill Loesch
Solar 1 - Saint Louis Solar






----- Original Message ----- 
From: "Kelly Keilwitz, Whidbey Sun & Wind" <kelly at whidbeysunwind.com>
To: "RE Wrenches listserve" <re-wrenches at lists.re-wrenches.org>
Sent: Wednesday, May 19, 2010 1:14 AM
Subject: [RE-wrenches] SWH - mixing valves


> Thermal wrenches,
> I'm having an ongoing issue with mixing valves in my own system not
> keeping a steady mix domestic HW temperature as the tank temperature
> varies with solar heating. If I set it for (say) 122˚F mix when the
> tank is 135˚, it seems to hold that differential at all tank temps -
> i.e. when the tank is hotter the mix is too hot (sometimes dangerously
> so), and when colder the mix is too cold for a comfortable shower.
> Thus, I need to change the setting all the time.
>
> I'm now using a Honeywell valve with a 90˚ - 145˚ range. This is a
> replacement for a valve with a wider range that acted the same way.
> Any ideas,  suggestions for better valves, or....?
>
> This has me wondering how many of our SWH customers are experiencing a
> similar thing, but just aren't bothered enough to say anything. We
> seem to have encountered many plumbing situations where the mixing
> valve allowed weird backflow or siphoning situations to mess with
> system operation, especially with HW recirculation. I thought I had
> all such causes eliminated on my system, but maybe not.
>
> Thanks for sharing your experience with such matters.
> -Kelly
>
> Kelly Keilwitz, P.E.
> Whidbey Sun & Wind
> Renewable Energy Systems
> kelly at whidbeysunwind.com
> 360-678-7131
>
>
>
>
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