Boiler pump choking when Tado closes too many radiators


if only a single room needs heating, tado requests heat from the boiler. Then, it takes some time for the radiators to open. During this time, the boiler pump chokes. My boiler has a built-in bypass, so the systems doesn't go into error, but it makes a lot of noise and it can't be good for the pump to do this on a regular basis.

I do have two radiators open all the time, but apparently this is not sufficient. Any ideas how to solve this? Would it be possible to set a delay, so that Tado first opens the radiators, then, after the delay, requests heat?


  • davidlyall

    How much of a delay are you seeing between the call for heat and the radiator opening?

    In my experience, the Tado TRVs are open before the extension kit relay clicks to turn on the pump and boiler.

  • Nyssel
    Interesting. I am not using the extension kit, just the smart thermostat, which acts as the zone controller, and a number of TRVs.
    I can hear the boiler starting up, then 2 or 3 seconds later I hear the TRVs opening.
  • An extension kit clicking will usually tell a motorised valve to move. The switched live won’t be active until the valve reaches its final position. The switched live will then activate the boiler. Often, the pump is directly under boiler control. It’ll take a few seconds to complete.

  • Nyssel

    @Montage so, without the extension kit, the boiler will be activated immediately. And still, the TRV's take some time. Correct?

  • I don’t have any, so can’t help with that.

  • johnnyp78
    johnnyp78 ✭✭✭
    On my system, with an extension kit linked to the boiler by Opentherm, the trvs open before it turns on the boiler. However when the trvs close, the boiler pump usually keeps running for a couple of minutes afterwards.
  • I have noticed a lot of pump noise when just one radiator is calling for heat, so most of the valves are closed but the pump and boiler are running.

    I don't blame tado for this, the problem must be just as bad with "old fashioned" TRVs.

    I'm thinking of fitting a modulating pump. I think they work by monitoring the back pressure in the system.