How to limit in-floor water temperature in my system?

nano_o

Hi all, I have a new question about my janky radiant system. I started measuring temperatures and realized that it's sending water up to 180 F to my floors (concrete floors; tiles on top are all cracked, maybe because of the temperature).

There is a thermostatic diverter valve (the black valve on the picture) with a sensor on the pipe going to the in-floor, which I presume is there to limit the temperature of the water. If so, it's not doing its job. I tried different setting and the temperature never changes, so it might defective. However, the valve seems to be an Oventrop Uni LH, which has an adjustment range of 45 to 82 F. If so, it can't possibly work.

What do you think? Am I wrong about the temperature range of that valve? Or am I wrong about what it's supposed to do?

In any case, I would like to be able to limit the temperature of the water going to my floors. Any suggestion on how to achieve that? Can a diverter valve at that spot possibly achieve that?

I asked a different question about this system a few weeks ago. Discussion is here:

https://forum.heatinghelp.com/discussion/comment/1837158#Comment_1837158

psb75

It would be more helpful to us on this forum if you provided a well-drawn schematic of your system. The photos are confusing and do not provide full context.

Jamie Hall

If my interpretation of the photo and your arrows is correct — kind of hard to read — there is no way that is going to work as piped, whether the mixing valve is the right one or not.

To use a mixing valve, the cold (return from the floor) has to connect to the cold inlet of the valve. The hot (connection to the boiler supply) has to connect to the hot side. The outlet (the centre outlet on the valve) has to go to the pump which in turn pumps into the floor.

nano_o

@Jamie Hall The previous occupants have been relying on it for the last 25 years, so it's working in a way. It's my first winter in this house. About the black valve on the picture: the pump is pushing cold water (return from the floor) into the inlet of the valve (label I) and then the flow splits in two: back to the boiler (label II) and back to the floor loop (label III). So it's a diverting valve right?

@psb75 okay I'll try to draw a schematic.

pecmsg

working or working properly?

HVACNUT

https://forum.heatinghelp.com/discussion/comment/1843067#Comment_1843067

Its not correct. The supply should be 1, return 2, mix 3, with the circulator on the mix side. You don't pump into a mixing valve.

Kaos

I think that is a boiler protection mix valve, the mix port is not in the center.

Can you get the part number of the mix valve and post it.

nano_o

it says DN 25 PN 16 on the back

hot_rod

DN is the pipe size, PN is the pressure rating in bars

That valve shows up in Oven trop catalog as a 3 way diverting or 3 way mixing valve.

Most manufacturers have legacy valve data somewhere on their sites.

Its possible the valve is stuck in one position or the thermal cartridge inside has failed, if it is not regulating properly

It looks old enough to need some maintenance or rebuilding

IMG_9702.png

Kaos

Pop off the actuator from the valve and see if the valve works. There is a center pin on the valve, that should move with a bit of force (spring loaded).

You can also take the actuator and put the sensor bulb in a pot of boiling water to see if it works.

nano_o

@hot_rod Thanks! That looks like it.

hot_rod

You do want to be careful checking thermal or oil filled actuators. They want to be attached to the valve when testing with hot or ice water. If you remove it the pin inside the thermal motor may over-stroke and blow apart.

Here is an example of what is inside some thermal operated valves.

Basically a copper capsule with a mix of paraffin wax and ground copper. Heat applied causes the wax to warm and expand. A very simple technology.

On a capillary tube actuator you have there is usually a mineral oil inside the cap end and that small tube, instead of wax. It is not a wire.

Those small tubes can get pinched or broken.

So either the capillary tube portion is bad, or the pin inside is stuck from dirty water.

Screenshot 2025-02-17 at 9.39.18 AM.png

nano_o

Thanks, that's good to know! If I break the actuator and don't put it back on, will the valve be stuck with the straight port open? (in which case the system would still work). Another issue is that I'm in the US and it looks hard to find anything Oventrop. Let's say it's the actuator that's faulty; are there other brands that might work as a replacement?

hot_rod

Oventrop closed down the US operation, you may need to shop the UK sites for parts or just replace the entire valve if parts are obsolete

The cutaway pic shows the flow path when the actuator is removed, but Im still not clear if it is being used as a mixing valve or diverting, on your system. So, hard to know what happens with the actuator off.

Is the sensor on a supply or return pipe?

Try it and see, what do you have to lose?

nano_o

Sensor is on the supply pipe like in my drawing below.

At the moment the system is providing heat to the house, even though the floor temperature is way too high. No heat at all would be more of a problem…

hot_rod

https://forum.heatinghelp.com/discussion/comment/1843303#Comment_1843303

Id wait until the end of the heating season to tackle that valve with unknown parts availability