Help selecting a tempering valve

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Chesterton

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I have a Rinnai tankless that supplies domestic hot water. When it's particularly cold out it also provides hot water to a heat exchanger in the HVAC ("emergency heat"). Consequently, the controller on the Rinnai allows it to heat to 185 degrees. There is currently an Apollo TV 34-200 thermostatic tempering valve that mixes it down for domestic use.

For the last couple of years the max water temperature we could get was about 97 degrees. After completely rebuilding my Rinnai I realized that the problem was the valve (which I have now confirmed).

The installer of the system sweated in the Apollo valve. I would like to replace it with a Caleffi and convert it over to NPT so I can change stuff, rebuild, etc., later more easily.

Can someone provide direction on a valve? For example, I believe that this one will work: https://www.caleffi.com/usa/en-us/c...nd-pressure-balanced-mixing-valve-npt-521400a

Any other suggestions? Thanks!
 

Uhmgawa

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The OP is likely long past this. But I I've been using (and replacing every few years) the Taco 70A tempering valve I'd originally installed for DHW on my boiler decades ago. It was the local el-cheapo contractor favorite at the time (in New England) and a whopping $15 at my supplier. Worked (sort of) at first then like crap after a year but really inexpensive to replace. After Taco decided to up the price for that junk near that for real tempering valves, and considering its performance was always horrific, I tossed it in favor of a Honeywell/Resideo AM100 and was shocked by the improvement. You install, set it, and forget it. Plus it is available in a sweat union termination so even in the case of maintenance cleaning 5+ years later, keeping a hot spare reduces down time to a few minutes vs. that for a direct sweat install. My only regret is not punting the Taco brain fart tempering valve years ago. Live and learn..
 

Fitter30

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Are you trying to drop temp from what temp for dhw. If your running 150° contact the tech dept for a recommendation for a valve since the flow will very greatly on the dhw side. Your using a separate heat exchanger dhw to heating loop? What model of the Rinnai tankless?
 
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