Mixing valve recommendations??

Hello everyone! I need some advice on a mixing valve in a domestic water system. Here is how my system is set up. I have a wood/coal furnace with a hot water coil that thermosiphons into a 50 gallon storage tank. This usually supplies enough hot water when its cold, but on a warmer day it gets behind. We then have a tankless hot water heater we can switch over too on the warmer days or when the stove is not going. What I was thinking of doing is installing a mixing thermostatic mixing valve between the storage tank heated by the stove and the tankless hot water heater. This way on a warmer day or a day when the stove is not going, I don't have to swich valves. I need to cool/temper the water that goes into the tankless as it can not have incoming water over 100 degrees. Do you think this will work? Anyone have any recommendations on what brand/model of mixing valve to buy?

Thanks!
Ben

Taco, Watts & Honeywell are the popular ones. But, I think the Watts only goes down to 120 degrees. The others go down to 70 or 85....just watch the specs.

Personally, Honeywell's are my choice.

Be sitting when you look for the price!

Freddy wrote:Taco, Watts & Honeywell are the popular ones. But, I think the Watts only goes down to 120 degrees. The others go down to 70 or 85....just watch the specs.

Personally, Honeywell's are my choice.

Be sitting when you look for the price!

Thanks Freddy. I looked at a few of them before and yes I was a little shocked at what they want for them. I also bought some brass fittings a couple of days ago and was a little shocked when I paid for them. I'll go with the Honeywell based on your opinion. I do have one more question regarding mixing valves. What happens when they fail?? Will they allow too hot of water to go past them? or will they only allow cold? The reason I ask is that I don't want to ruin my tankless if the mixing valve would happen to fail. I've had new things fail right out of the box so I've learned that a guy can't be too careful.

Thanks!
Ben

Ben, they usually fail due to mineral or sediment buildup. Install the appropriate ball valves and drains to the coil can be flushed down the road if necessary.

Like Freddy, I like the Honeywell units.

Just buy a hard seat globe valve and adjust manually. Nothing to go wrong.

franco b wrote:Just buy a hard seat globe valve and adjust manually. Nothing to go wrong.

What he said!

I like symmons, but for your application, a couple of globe valves.

I would go with a globe valve setup, but the preheated water can vary in temperature quite a bit. When its warm out, it doesn't produce much hot water, but when its cold, it can get very hot. I don't want the possibility of sending any water over 120F to my tankless. Thats why I would rather go with an automatic mixing valve. I am considering a Honeywell AM101-UT-1. The only thing I have a question about now is this: In the Product Information there is a statement that reads : Minimum required temperature difference between hot and mix is 3F. What does this mean? Does this mean that if I have the valve set to 100F and my water is only 90F it will not work? I was under the thought that it would just open up and allow full hot flow when hot temperature was under the temperature setting on the valve? What are your guys thoughts?? I tried calling honeywell three times and they won't answer my question because I am not a licensed contractor. I got pretty ornery with the one guy with still no luck.
Thanks guys!
Ben

Sounds like your building a contraption

Thats just my style

you need to limit the incoming energy - thats the job of an anti scald valve - not a mixing valve they do the opposite

think about the possibility for minute - you have come this far - just a push in the right direction

Sting wrote:Sounds like your building a contraption

Thats just my style

you need to limit the incoming energy - thats the job of an anti scald valve - not a mixing valve they do the opposite

think about the possibility for minute - you have come this far - just a push in the right direction

I'm not sure what you mean by saying that an anti scald valve and mixing valve do the opposite things. From what I've encountered there are a couple of names these can be called. Tempering, mixing, antiscald. They all mix hot and cold water together to reach a desired temperature. I could very well be wrong but thats the way I understand it. Anway, here is the one I am planning on using: http://www.pexsupply.com/Honeywell-Spar ... 10643000-p

Ben

Some time ago - I learned all sort of things about what my mother used to do for quarters from a candidate that I attempted to redirect in his methods of piping mixing valves

I really don't need that again

so: let me just write that a mixing valve is piped to take hi energy liquid - mix it with low energy bearing liquid - and pass the result out to the load.......

[you] on the other hand [appear] to have an abundance of hi energy liquid that you want to pass to the load as a liquid of lower energy = thats the job of a shower valve

both valves are built to do a very different job in how they react to input and output of liquid -

When it comes to "contraptions' anything is possible as long as you don't have to do it yourself - and advice is like the seat of my pants - I have both - sometimes one is considered better or just bigger than umm the other

so once more, the correct answer is "It depends"

Sting wrote:Some time ago - I learned all sort of things about what my mother used to do for quarters from a candidate that I attempted to redirect in his methods of piping mixing valves
I really don't need that again
so: let me just write that a mixing valve is piped to take hi energy liquid - mix it with low energy bearing liquid - and pass the result out to the load.......

[you] on the other hand [appear] to have an abundance of hi energy liquid that you want to pass to the load as a liquid of lower energy = thats the job of a shower valve

both valves are built to do a very different job in how they react to input and output of liquid -
When it comes to "contraptions' anything is possible as long as you don't have to do it yourself - and advice is like the seat of my pants - I have both - sometimes one is considered better or just bigger than umm the other

so once more, the correct answer is "It depends"

Try holding it upside down sometimes that helps.

Okay guys, let me simplify this. I have one simple question. THAT QUESTION IS: When a "mixing valve, antiscald valve, whatever you want to call it" is set at 100F and your hot water going to it drops to 90F what happens?????? Does it close or shut off or does it continue to flow water allowing only hot water to flow through the valve and not mixing in any cold water???

Thank you!
Ben

bverwolf wrote:is set at 100F and your hot water going to it drops to 90F what happens

It flows the 90 degree water.... or perhaps still mixes a small amount of cold in with it. It does not shut off.

Thank you Freddy! Thats what I was hoping.
Ben