Mixing Valve & Radiant Floor Heat??

With the KA-2 in the basement it is getting close to the time to do the boiler piping. Since I want to run the boiler at about 140-150F but only need maybe 120F throught the pex will a 3 way mixing valve do? Or do I need to consider using a 4 way valve and have the 4 inlet cold water coming in?
Today I finish installing manifolds and starting to pressure test.
Thanks,
Tom

You want to run that boiler a bit warmer...
160*-170*, 180* would be a better start until you learn the heat load...
140* is condensing temp. and you can rot out the inside of the boiler...
If the returning water drops the temps too much the moisture and coal gases combine...
Giving the inside of the boiler a nice acid bath...

Ok ,that makes sense. But if I run it that hot can I can the temp down to 120-125F by using a 3 way mixing valve that uses the return water? This is where I am stumpted.

Morning Tom,

Maybe I just need more coffee but I am not sure about your vision on this 4 way valve idea. The three way valve will work fine - until it sticks. IMO they all do, and in that Ill recommend you not use the solder in types.

You can do the same with two quarter turn valves - Globe valves would be nicer but too costly for most. Be sure to place temperature wells so you can monitor your reduced supply (at least) and return temperatures.

Pump placement for these zones is critical if the mixing system or valves are to work properly. The pump must be on the load side of the flow diversion and I prefer it placed to suck on the return loop of the load. But that's just me, others may cast dispersions from here.

Kind Regards
Sting

Kungur wrote:Ok ,that makes sense. But if I run it that hot can I can the temp down to 120-125F by using a 3 way mixing valve that uses the return water? This is where I am stumpted.

yes

you can run as low as 90 degrees in the shoulder seasons -- just enough to pull the chill off the floor and have a nice comfortable shower room floor when its 50 outdoors.

you can use a thermostatic mixing valve. these valves are specifically designed for radiant heating. They use hot supply and cooler return water to temper as per the dial setting. a lot easier than 1/4 turns and much more consistant with regards to maintaining water temps. These valves self adj. to incoming water temps. therefore you will get a solid 120 deg output if the boiler water is 140 or 180. A little pricey, but they work (125.00) Set it and forget it.
Frank

CapeCoaler wrote:You want to run that boiler a bit warmer...
160*-170*, 180* would be a better start until you learn the heat load...
140* is condensing temp. and you can rot out the inside of the boiler...
If the returning water drops the temps too much the moisture and coal gases combine...
Giving the inside of the boiler a nice acid bath...

I played with lower settings last spring. What a mess! The prior 5 months, running at 180+*, the boiler stayed nice and clean. I ended up shutting down, cleaning out, and spraying the entire inside with baking soda & water to nutralize any acids. The whole inside fizzed away, as if I were useing it on battery acid. And stink...............As capeCoaler says, don't run at lower temps. I won't ever do it again.

do I put in a tee between the pump and boiler on the return side?

PelletstoCoal wrote:you can use a thermostatic mixing valve. these valves are specifically designed for radiant heating. They use hot supply and cooler return water to temper as per the dial setting. a lot easier than 1/4 turns and much more consistant with regards to maintaining water temps. These valves self adj. to incoming water temps. therefore you will get a solid 120 deg output if the boiler water is 140 or 180. A little pricey, but they work (125.00) Set it and forget it.
Frank

Why not use something modern

http://tekmarcontrols.com/accessories/712.html