[RE-wrenches] SWH - mixing valves

[Kelly Keilwitz, Whidbey Sun & Wind]

Doug,
I HAVE had tank (SS) temps in excess of 180˚, but rarely. These valves  
are the Honeywell Sparcomix AM series. I don't see any temperature  
limitations listed in the specifications.
-Kelly

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

On May 19, 2010, at 6:48 AM, Doug Wells wrote:

> Kelly,
>
> I have also seen mixing valves get leaky over time.  Many mixing  
> valves are designed for controlled input from a boiler at steady 140  
> degree temps.  It is not uncommon for SHW tanks to reach 180+  
> degrees in certain conditions.  If exposed to these higher temps the  
> valves can begin to loose accuracy.  Usually they are designed to  
> "fault" into the cold position, so the begin to leak in a little  
> cold and the client will complain about low temps at the faucet/ 
> shower.
>
> Doug Wells
> The Solar Specialists
> Morrisville, VT 05661
> (p) 802-223-7014
> (c) 802-498-5856
> www.thesolarspecialists.com
>
> On May 19, 2010, at 2:14 AM, Kelly Keilwitz, Whidbey Sun & Wind wrote:
>
>> 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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