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
ke...@whidbeysunwind.com
360-678-7131
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