Mixing valve not adjusting

DrVit

After installation of radiant, for some reason I can't adjust temp to be anything other then 145-150. While mixing valve manual is stating that default is 115-120, my gauges are showing 145-150. tried to turn knob clockwise about 1/4 turn, but it just seems to be spinning around with no effect. Any suggestions on what could be wrong?

Intplm.

What "mixing valve "are you referring too. I do not see one in the pictures.
Why not send a few more pics. Maybe then we can get somewhere?

Larry Weingarten

Hi, Is the valve to the right of (under) the pump?

Yours, Larry

GroundUp

Looks like your boiler circ is pushing toward the expansion tank and shoving water into the hot port of the mixer, occluding the thermostat in the mixer. If you throttle that ball valve on the supply pipe to the mixer, does it adjust somewhat? What brand mixer is that?

Intplm.

Now I see it........thanks to the above.
Please send more pics. Especially of the mixing valve.
Please state as best you can what you are trying to accomplish.

DrVit

Apparently didn't mark this treat to get notifications, so just saw all comments Also sorry for photo being horizontal.
1. Mixing valve is under the circ pump on the picture. I can upload a photo of the mixing valve later.
2. On the bottom of the MV, it has triangle nob, which could be turned one way or another. It goes all way around, and doesn't have "min/max" settings.
3. Feed from the boiler is a line with air scooper on the top (line coming to MV from the right). Connected to hot inlet of the MW
4. Return from radiant is line on the left, connected back to the return manifold and feeding MV to "Cold" inlet

Radiant is generally working, so looks like piping and connections are right. Problem I have - while in MV instructions it said that by default it set for around 120F, and I can adjust radiant supply from like 80-180, I can't seems to find a position to lower loop temp from 150 to 130. That is basically my objective - to decrease loop supply temp. As currently floor temp is around 90, with supply showing 150/145. Maybe I keep turning nob too much, or don't give enough time for MV to adjust (I tried to turn like 1/4 turn, waited about 5 min to see if temp will change, then turn another 1/4, wait 5 min). Now I'm thinking that I probably should give more time for water to cool off before I try to adjust it.

hot_rod

A few things to know about thermostatic 3 way mix valves. They need a minimum amount of flow to regulate accurately, the manufacturers data should indicate this GPM. On small valves .5 gpm, larger sizes may require 1 gpm or more. This assures the wax "motor" inside gets good turbulent flow around it to heat evenly.

Also a temperature differential is required, most are 20- 27°. In other words the hot supply to the valve needs to be at least 20° warmer than the mix temperature you are trying to achive.

If that differential is not assured the valve will be unstable, temperature goes up and down as the valve "hunts" for a stable operating condition. Flow can never stop completely, just the mix temperature is thready.

And it could just need a rebuild, the cartridges stick and temperature seems to make big jumps instead of even outlet temperature, or o rings fail and you lose mixing resolution, copper heat motors inside fail also.

DrVit

@hot_rod
- its brand new valve.
- GPM should be plenty, as its new install with only one loop atm ~ 180' and 3/4" copper extended header ~ 50'
I'll make more pictures and MV brand name next time I'm in that house.
Thanks guys for all your inputs

Erin Holohan Haskell

Here's the photo right-side up:

DrVit

Thank you Erin ! Don't have to turn my head now

Erin Holohan Haskell

DrVit said:

Thank you Erin ! Don't have to turn my head now

You're welcome!

DrVit

Few more photos attached. Even though specs are saying MV is for 85-176, it doesn't look that turning adjustment knob does anything. I lowered boiler temp to 160 now. MV supply is still ~ 150. I can lower it to about 130 by closing supply valve almost to shut position, but its not the way MV should work. Considering valve was brand new, could anything be screwed up during install?

Intplm.

@DrVit. Those Taco thermostatic mixing valves are pretty darn good valves. The ones I have installed use the cap, a green cap that it comes with as a "key" to make temperature adjustments. Does this valve have come with a green cap to do this?
Also.
Theres possibly some debris stuck in the valve. Maybe solder during installation or maybe something else. Either way, I would take the valve apart and clean it.

kcopp

Intplm. said:

@DrVit. Those Taco thermostatic mixing valves are pretty darn good valves. The ones I have installed use the cap, a green cap that it comes with as a "key" to make temperature adjustments. Does this valve have come with a green cap to do this?
Also.
Theres possibly some debris stuck in the valve. Maybe solder during installation or maybe something else. Either way, I would take the valve apart and clean it.

The cap is on top of the Low water cutoff.

From the last pix I see the radiant return goes into the suction side of zone valve circ pump.
This could interfere w/ how the valve works when the zone valve circ pump is on. That return should have gone back to the boiler after the circulator.

DrVit

I pulled MV off, and both valves seems to be moving freely. @kcopp , yes, it came with green cap, which I use to turn triangle knob. As far as primary circ affecting - theoretically it could. I'm assuming that your idea is that its pulling water from the radiant loop and causing hot side to add more hot. But if that would be a case - isn't idea of the MV just to shut hot side when set temp is reached? On the same note - could my return side somehow affect cold size?
SPECIFICATIONS:
Hot Water Inlet Temperature: 120-180°F (60-82°C) Factory Preset: 115-120°F (41-46°C)
Cold Water Inlet Temperature: 39-80°F (4-27°C) Outlet Water Temperature Range: 85-176°F (29-80°C)

My return is showing almost the same temp as supply with only few degree differential. So say if S is 150, R would be about 148.
Radiant pump is set on "1"

hot_rod

With multiple zones I prefer to see the mix valve pulled off a primary loop with P/S piping. This also assures a constant supply of hot across that port.

Another rule is that the boiler output should be 4 times the load of the low temperature zone. If so, a return protection valve is less critical.

DrVit

@hot_rod Thanks for your inputs. Considering this system was already piped with no P/S - I didn't intend to go into redoing whole system (especially considering I'm not a master plumber and doing plumbing just on occasions)
- not sure how to calculate hot output to be 4 times the load of low temp, but considering it cut right of the boiler H side - I assume there are should be plenty of hot supply. Also - problem I'm having - is to lower temp, not to increase.
- I called Taco tech support, after checking that nothing is stuck inside the MV - they've suggested to try another MV and they are suspecting that MV could be defective. Basically just considering that when you turn adjustment knob - something should be happening after certain amount of time, but it doesn't look that way.

hot_rod

Did you confirm that you are working with the spec of the valve? here is an example of a Caleffi spec, other brands would be similar although they may massage the numbers

Critical for "accurate" regulation is:

#1 gpm minimum, sounds like you have at least a 1 gpm flow?

#2 pressure differential, not usually a problem in hydronic applications

#3 temperaturas differential between hot supply, and mixed outlet. we suggest 27°, so basically the hot supply to the valve needs to be 27° warmer that what you are expecting at the outlet.

The valve will still flow if that ∆ is not met but the outlet temperature will not be stable, wander around what you are expecting.

Without instrumentation, you may be just guessing?

I've taken the guts out of 3 way thermostatics in the past and run them. This assures and eliminate flow questions. It will be an unpredictable mix temperature, but can eliminate a flow restriction question in the circuit.

DrVit

@hot_rod . From what I see on the boiler - I can say that temp is set for 160 now, pressure last I've checked I believe was ~ 16 psi. Considering that all zones are working fine - I'd say that all parameters are good. New radiant loop is warm (too warm, 140-150) as well, so I don't see a flow inside the system being an issue. I bought new MV today and will try it next time in the house. But after thinking on @kcopp and your comments - my question is what would happen say if no other zones will be calling besides radiant? If boiler circ will still be pulling water (and it will, as radiant control will call for it), and all zone valves are closed - its logical that it will start pulling water from the radiant loop. And if pressure will drop there - then theoretically both radiant circ and boiler circ will try to replace lost water from the hot side. Thus keeping supply temp always hot. While MV suppose to mix cold from return, what will it do if there is not enough flow on cold side (as boiler circ will be pulling it out) ? I think this might be a reason of why loop supply is always hot and can't go lower - as pumps are constantly getting hot into it.

What @kcopp said about piping return on another side of boiler's circ might help somewhat, but would that solve problem if say no other zones are calling? It still will be pushing hot into only open zone (radiant). And if that's a case - then would radiant work properly at all w/o doing P/S?

I'm wondering if I should try to disconnect TT to boiler so at least boiler circ not pulling when other zones are closed. Also will try to maybe restrict flow on hot feed and back into main return.

P.S. More challenge than I've expected I will be installing more loops in the future on the same line, so that should also help with lowering return into the mix.

DZoro

With no zones calling your main boiler circ pump is "looking for its water" and is taking everything it can get from your mixing loop return, and is winning the battle with the mixing loop pump.
I'd be willing to bet it works fine when 2 or more other zones are calling.
D

DrVit

@DZoro I didn't notice much difference with or w/o other zones calling, although I didn't test that idea specifically. But considering radiant return is the closest to the boiler circ - I think its pulling water from there either way. I was able to reduce S temp of the loop to 130 by closing H valve to almost nothing. So guess for now can just try to close Hot and Return valves to restrict out-of-the-loop flow.

Jean-David Beyer

I cannot tell from the pictures, but if you run hot into the cold inlet, and cold into the hot inlet, it will not work right. I am not saying you did that, but you might want to check it to be sure.

DrVit

@Jean-David Beyer piping was checked. It is correct. Thanks for insight though.