Does radiant hydronic in floor heating require mixing valves?
We have six zones in our in floor heating, but no mixing valves or thermometers. We have hardwood, tile an carpet in various parts of the house. Currently the water temp under the hardwood is running too high for the wood to bear. We are trying to determine whether we need to have mixing valves installed to make the heating system safe and operable, or if they would just be a "nice to have".
The theory is that hydronic under floor heating, that is encased in concrete should have mixing valves, to stop the concrete cracking.
Where I have laid re inforced concrete, I have never used mixing valves, nor have I had any cracking, merely relying on normal thermostat valves. Normal none reinforced concrete probably does crack.
I must also write, that where I have fixed hydronic under floor heating under wood floors I have never used mixing valves, and over 40 odd years I have never had a problem. You can always turn the boiler thermostat down, to lower the temperature of the water.
Do ensure that you have at least six inches of polystyrene insulation below the pipes to keep the heat up in the room.
Note: Hot water pipes radiate heat through 360 degrees, and you are trying to heat the room above.
If your using the boiler for heating radiators as well then yes. The mixing valves allow you to run at different temperatures in different zones. I like putting them in because it gives so much more control over comfort. Slab concrete and tiles operate at about the same temp, it sounds like you have your water temp too high because wood floors should be less and if your wood floors are too hot then your concrete or tiles must be very hot. Radiant floor heating works on the principle that gently heating a large mass will produce the same amount of heat energy (btu’s) at lower temperatures than heating air at high temperatures (which gives up that heat easily). Loops lengths are a concern too, if they are not sized right, you could end up with uneven heat or worse cold floors at the end of a run and very hot floors at the beginning (close to the boiler). In that case you’d need to contact a tech to try and separate the loops and install mixing valves to balance it all out. Planning is the key to properly working radiant floor system.
Do you have any valves anywhere coming from the floor that is to hot? You could close down the return line some to throttle down the water it shouldn’t be done with a ball valve or gate but its better than messing up your floor. And if no valve have a globe valve or circuit setter installed in the return line shouldn’t be much to add. But i think for mixing valves you need chilled water too