[RE-wrenches] SWH - mixing valves

[Kelly Keilwitz, Whidbey Sun & Wind]

Bill,
The water is quite hard (30 grains/gal), but there is a softener on  
the DHW that lowers  the CaCO3 level significantly. I thought that  
this might have been a contributing factor with the previous mixing  
valve, but replacement (~2 years ago) didn't address the problem.  
Other than hardness minerals are quite low.
-Kelly

Kelly Keilwitz, P.E.
Whidbey Sun & Wind
Renewable Energy Systems
kelly at whidbeysunwind.com
360-678-7131




On May 19, 2010, at 6:26 AM, Bill Loesch wrote:

>
> 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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