Controlling the sometimes uncooperative Mixing Valve

[Don2222]

Hello

My friend got a new boiler and because of extremely limited space it had to have a tankless coil for DHW. Due to code requirements a mixing valve must be put in on the tankless hot output.

So we put in a ball valve on the cold input to the mixing valve so when the spring scales up inside we can cut down the cold and still get some hot water.

We tried it out and shut off the cold and got some really nice hot water for the sink and shower!

I do want to mention that there are no children around that would run the faucets too hot. Also he can open the ball valve and go back it he wishes.

So I do not recommend this but those mixing valves do NOT work well and if used properly this might help get a little more hot water when really needed without calling the boiler emergency number!

Has anyone tried this?

 

[jebatty]

My radiant floor mixing valve works very well. I have it set at 100F, and actual output ranges between 95-105F while boiler supply ranges between 120-190F. Obviously I could set the valve to a higher supply temperature if needed. I can't imagine why a mixing valve for DHW wouldn't work just as well.

I could say a lot more about safety, but since you are aware of the possible disfigurement or worse from a hot water burn, I don't need to say more.

 

[Don2222]

My radiant floor mixing valve works very well. I have it set at 100F, and actual output ranges between 95-105F while boiler supply ranges between 120-190F. Obviously I could set the valve to a higher supply temperature if needed. I can't imagine why a mixing valve for DHW wouldn't work just as well.

I could say a lot more about safety, but since you are aware of the possible disfigurement or worse from a hot water burn, I don't need to say more.

DHW contains minerals that deposit on the spring in the mixing valve and tankless coil eventually causing certain. Failure !!

 

[tom in maine]

Taco and Watts "mixing" valves, work some times. If you read the literature that comes with them, you have to wonder what the purpose of them really is.
The literature is full of "weasel language" that basically says don't count on them to work.

Anyone installing a temperature control on a thermal storage system (We can consider a boiler with a built in coil in this category) needs to use
an antiscald valve. They are built to ensure that the water that comes out of the tap is whatever you set it to and it stays there.
They might eventually scale up, but from my experience it is a long time and they are serviceable.

One such valve is the Sparco, which Honeywell owns. We had at one time a UL listed 150g unpressurized tank that we sold with an off-peak electric
heater that heated the tank to 180F every night when the rates were low. We could not rely on any common "mixing valves" to perform properly.
And UL would not accept anything but consistent safe hot water temperature.

That was a hard learned experience since everyone used common mixing valves and they just do not work right.
Sparcos cost about $100 but are worth it if you want safe DHW.

 

[jebatty]

DHW contains minerals that deposit on the spring in the mixing valve and tankless coil eventually causing certain. Failure !!

Thanks for the info. A person never stops learning.

 

[Don2222]

Hello

Good to know about the Honeywell Mixing valve. Thanks

From Amazon.com http://www.amazon.com/AM101-US-1-HONEYWELL-THERMOSTATIC-UNION-SWEAT-100-145F/dp/B002DGEOJC

AM101-US-1 HONEYWELL SPARCO THERMOSTATIC MIXING VALVE 3/4INCH UNION-SWEAT 100-145F

 

[Nofossil]

I've never had any luck at all with the Watts valve pictured in one of the earlier posts. I like the Honeywell AM101 because 1) It works, and 2) it can regulate an output temp to within three dgrees of the inlet temp - pretty impressive.

I have had problems with them freezing in place so that they continue to regulate but you can no longer change the outlet temp.

 

[jebatty]

Wonder of wonders. I have the Sparco as the mixing valve to mix down my supply to radiant floor. Got a good deal on it on *bay, no intelligence on my part in making the choice.

 

[Willman]

To my knowledge the valve pictured in OP is called a "tempering valve". That is about all they are good for.Not precise at all.

Will

 

[woodgeek]

Hey, I had the Honeywell installed on my tankless coil DHW about 4 yrs ago, replacing one that looked like Don's but which had started to leak. Now the Honeywell is (1) frozen so it can't be adjusted (2) regulating really poorly for a miserable shower experience. In desperation, I have been bumping the boiler aquastat temp upwards from time to time, but that increases standby usage--I am currently over 20°F higher than the minimum that worked fine 4 yrs ago.

Any advice? My plumber is very expensive--is this an easy job to have them come and clean it out? The plumber who installed it signaled that he thought it wouldn't work for very long.

 

[tom in maine]

The newer Honeywell/Sparco's cannot adjust unless you remove the screw in the adjustment knob and lift the knob a little. This is a safety so someone does not adjust it too hot.

I suppose to protect us from ourselves.

If an older one sticks, they do come apart easily. If you are so inclined.

 

[woodgeek]

The newer Honeywell/Sparco's cannot adjust unless you remove the screw in the adjustment knob and lift the knob a little. This is a safety so someone does not adjust it too hot.

I suppose to protect us from ourselves.

If an older one sticks, they do come apart easily. If you are so inclined.

thanks much! I was hoping it was something like that...but hadn't a chance to investigate.