page 20
5
MIXIT WITH RADIATORS AND UNDERFLOOR HEATING
The underfloor heating and radiator heating applications of MIXIT controls the water temperature out of the
mixing loop. The two application settings only differ by the underfloor heating setting having an overheat
protection function that will close the valve and stop the pump in case the water temperature out of the
mixing loop increases above a set maximum level. If the underfloor overheat protection function is disabled,
the two application settings functions 100% the same, both are therefore treated in this section.
5.1
The build in underfloor overheat protection function
When the underfloor overheat protection is enabled the setpoint is limited 5 deg. C below the set maximum
level. This is to avoid triggering the overheat protection function in case of a small overshoot. The control
loop carried out by MIXIT is shown simplified in Figure 18.
Figure 18: MIXIT control loop with setpoint limitation, due to overheat protection function.
For example, if the overheat protection function is set with a maximum level of 50 deg. C and the given
setpoint is above the 45 deg. C. MIXIT will automatically limit the setpoint at 45 deg. C. if. The screen for
setting up or disabling the function in Grundfos GO is shown in Figure 19. Settings -> Application settings ->
Underfloor overheat protection.
Figure 19: Setup of the overheat protection function by Grundfos GO.
If the temperature increases above the set maximum limit the valve will close and the pump stop until the
temperature has decreased below the set maximum limit. This may take some time as the water standing in
the pump needs to cool down by natural convection.
