Buderus Mixing Station - How Does It Work?

jdbs3

Trying to understand how the flow of water through the mixing station work, and, in general, how the Tekmar 360 assures not too hot a water temperature is flowing through the Buderus into radiant floor PRX tubing.

Buderus mixing station is controlled by a Tekmar 360 controller.

What I know:

- Tekmar T5 – T6 (Output Mix System Pump) are connect to Buderus Grundfos circulator pump
- Tekmar T9 – T11 (Output Mixing Valve and Actuating Motor) are connected to Buderus Danfoss ESBE Floating 3-Point Signal Motor Actuator.
The 360 pulses the actuator motor open or close to maintain correct mixed supply water temperature at the mix sensor when there is a mixing demand… A visual indication as to whether the control is currently opening or closing the mixing valve is displayed in the
LCD.
-Tekmar T13 and T15 (Input Mix Supply Sensor) are connected to Buderus supply side temperature gauge. See blue wire to left of red supply temperature gauge.
- The mixing valve is behind the Danfoss ESBE ARA actuator.
- The Tekmar 360 uses current Mix temperature and Mix max, along with a characterization curve to open and close the mixing valve.

What I don't know:

There are 2 pipe connections on the Buderus between the supply and return side. So hot water could flow either through:

- Supply pipe to Buderus -> Buderus -> Supply pipe to radiant floor zone, and/or

- Supply pipe to Buderus -> L -> R through bottom connecting pipe on Buderus -> Return pipe from Buderus to boiler, and/or

- Supply pipe to Buderus -> L -> R through top connecting pipe on Buderus -> Return pipe from Buderus to boiler, and/or

- Supply pipe to Buderus -> L -> R through top connecting pipe on Buderus -> then R -> L through bottom connecting pipe on Buderus.

All very confusing! So I am trying to understand when does water flow through each of these pipe connections. Questions:

1. When the mixing valve is Closed, what is the flow of water through each of these pipes?

2. When the mixing valve is Open, what is the flow of water through each of these pipes?

3. If there is a call for radiant zone heat, does water always flow through the Buderus on the supply side and on to the radiant floor zone?

Thanks in advance for any insight on this, or a pointer to a document that explains it.

jdbs3

See attached picture

GW

It’s sort of simple- if the valve is open the zone is getting full boiler water. If it’s closed the zone is just circulating its own water. If it’s in the middle it’s doing 50-50. 

hot_rod

The motor actuator rotates the spool inside to get the desired temperature

The hot from the boiler is blending with the cooler return from the system to establish the desired mix temperature
A portion of the cooler return goes back to the boiler to be reheated and give you the higher supply temperature to the mix valve 

jdbs3

Much thanks. Now I understand.

What I was missing is that there are 2 loops: the radiant floor mixing loop, and the boiler loop. I also found this picture on this web site. See

jdbs3

https://houseneeds.com/learning-center/hydronic-heating-systems/heating-mixing-valve-setup