Leave last valve open until boiler stop commanded to avoid overpressure

Problem:

When all valves close and stop asking for heat, it can take up to a minute for the room thermostat to communicate with the boiler to turn it off. In my house, as all radiators have tado valves, this leads to a very noisy banging sound as the pump tries to push water around the circuit when every radiator is closed. In a manual system, plumbers leave at least one radiator in the circuit without a TRV to mitigate for this problem, but this seems silly and (should be) unnecessary for a smart solution.

Solution:

When the final radiator associated with a smart thermostat stops requesting heat, either:

  • communicate the stop request, but leave the valve open for at least 2 minutes to allow the boiler to stop; or
  • communicate the stop request and leave the valve open (also saving battery!). Close the value if necessary when the circuit is next activated and the boiler restarts.

Impact:

I have had to remove a tado thermostat from one of my radiators and effectively have no control in that room. due to this issue. I have two separate pumping circuits in my house; so that's a loss of two device sales I would otherwise have purchased.

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Comments

  • You need a bypass valve on your system. Even with one TRV removed you may overload the pump, or fail to achieve the minimum flow of water through your boiler. Modern lightweight heat exchangers are sensitive to over heating - some boilers run the pump independent of the thermostat control to dissipate excess heat. Not sure where you are located, but UK regulations mandate a bypass is fitted.

  • Oh that's interesting GrilledCheese. I am in the UK and there clearly isn't one. I guess I'll need to get that sorted.

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