How to call for Hot Water or Heating on a Vaillant Boiler

Discussion in 'Plumbers' Talk' started by Pete K, Dec 14, 2022.

  1. Pete K

    Pete K New Member

    I have a heating system configured with s plan wiring. There are two zones and one pressurised hot water cylinder. The are three 2 port motorised valves. 2 for the tow heating zones and one for the hot water cylinder. When the programmer calls for heat and the respective cylinder or room thermostat calls for heat the relevant valve is actuated and opens thus closing the internal microswitch this then starts the boiler. At this time all three 2 port valve microswitches are in parallel meaning that there is only one signal wire pair to the boiler. I have a Vaillant Ecotech 466 boiler. The manual can be found here:

    When any of the valves are open and hence the microswitch is closed 240v AC is applies to the RT pin on the boiler - the 240v coming from the boiler. Essentially pins 3 and 4 on the violet connecter as shown on page 23 of the manual and the boiler starts in heating mode.

    The boiler has the option to set the water temperature for the heating and hot water to different values but as the boiler is currently wired the boiler does not know what is being called for so only the heating temp control is used.

    Can someone tell me which connections I should use on the boiler to be able to call for hot water or heating as separate signals so that I can control these two temperatures separately
  2. Teki

    Teki Screwfix Select

    The boiler flow temperature should be >60°C. The temperature of the hot water is set by the tank thermostat which shouldn't be less than 60°C and the temperature of rooms is set by the room thermostats and TRVs.
  3. quasar9

    quasar9 Screwfix Select

    Yours is a system boiler. Vaillant uses the same display/control panel for their combis too, so the hot water temperature control with a tap symbol does nothing although the LCD shows a value that changes with the control. Only the other control with the radiator symbol works.

    Rest as Teki says. That boiler flow temp is the control with rad symbol
  4. Davie

    Davie Active Member

    Modern thinking is that condensing boilers operate most efficiently at about 55°C
  5. Teki

    Teki Screwfix Select

  6. Mike83

    Mike83 Screwfix Select

    Can probably gain more control with the individual temperatures but you will need to fit all Vaillant controls and that will be expensive

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