mixing valve or diverting valve?

Ken_25

Modern hydronic heating talks about 3 way mixing valves for controlling supply water temperatures for floor heating, and 3 way diverter valves for controlling solar storage tank usage. My supply house says they have one valve called a mixing valve/ diverter valve. Are they the same valve with two different names? Therefor is a mixing valve system the same as a diverter valve system?

bob_46

3-way

A mixing valve has two goes into ports and one goes out of port. A diverting valve has one goes into port and two goes out of ports ( and costs a lot more).

Ken_25

confused by picture

Siegenthaler's Modern Hydronic Heating has a picture of a diverter valve on page 70, but it only shows one direction of flow arrow. can someone explain how the flows could work in that diagram.

Ken_25

diverting valve doesn't mix?

Further study leads me to believe a mixing valve mixes two sources to give a blended output. A diverting valve gives you a choice of two inputs but does not mix the two sources. You get either input 1 or input 2 as your output . Am I on the right track.

Brad White

Yes you are.

What Bob said is essentially correct (I was not aware of a cost difference, that may or may not be).



Your take is also correct, basically a diverting valve, think if it as a train track switch, sending the incoming train one way or the other.



A mixing valve is also like a train switch, taking two trains onto a single track but the switch is operated by Snidely Whiplash to cause a collision.



As another point of distinction or way to look at it: A mixing valve is most commonly on the suction side of a circulator and a diverting valve on the discharge side.

Mark Eatherton

One will work as both, but not the other...

I had a job recently where the installers had mistakenly set a diverting valve in a mixing valves position. I tried to make it work (non electric) but could not get it to work. It just kept flooding, and would not get up to the temperature I needed. A diverting valve can only be used as a diverting valve, and will not function as a mixing valve, regardless of the controls being applied.



A mixing valve, on the other hand COULD be used as a diverting valve, but would be a rather expensive diverting valve with an inherently high pressure drop, so it is more expensive in more ways than you can actually see.



Once I'd replaced the diverter with the mixer (Oventrop) it kicked right in and started delivering the comfort that the consumer expected, but had not experienced in his 4 years of ownership, and having had 1/2 a dozen different heating techs in to figure out why.



The hot and cold ports of a mixer are proportional, whereas a diverter is not.



A diverter usually comes with the ports marked differently than a mixer. If memory serves me correctly, the diverter ports were numbered (1+2=3), and the mixer ports were alphabetized (A, B, AB).



Attempting to use a diverter as a mixer will not result in satisfactory control, and will cause discomfort.



JMHO and field experience.



ME

Ken_25

Thankyou all.

This has been a great help. Siegenthaller's book usually answers all the questions if I study it enough, but this one had me stumped.

Ken

bob_46

Mix

Mixing valves are commonly used as diverting valves but not the other way around.

Here is a common set up used to control the temp. of a coil. The valve sends supply

water to either the coil or the return or some proportion there of if it's modulating.