Should my pump overrun for any length of time?
Just replaced my old Drayton controller/programmer so I could link the heating to my home automation setup using the Tado V3+ stat. All going great, but I noticed that my pump was still running after the heating had gone off the other day, had been running for at least another 10-15 minutes before I noticed. I turned the heating and hot water on briefly then turned it off which knocked the pump off. Had the valves checked which are all fine, and less that a year old, wiring for the hub checked too which is all fine. So, is their some kind of overrun feature as the heating and hot water were definitely off. Just can't work it out. Note I've a pressurised system.
Answers
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What is your boiler make/model ? Most modern boilers will have a pump over-run function to dissipate excess heat through an internal or external bypass.
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It's a Grant Vortex oil boiler, 15-26 model I think. It seems it only happens when the boiler has been on for a long period, say 3-4 hours. Can't find anything on an overrun feature for the boiler though. It makes sense for it to happen if the heating has been on for long periods, it just never happened with the old Drayton controller.
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Have you fitted thermostatic valves on all the radiators? If so, the system should have an external automatic bypass after the pump. Otherwise an unrestricted radiator will probably do the job.
Boiler manual, page 22: If thermostatic radiator valves are fitted to all radiators, a system by-pass must be fitted. The by-pass must be an automatic type.
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All radiators have thermostatic valves and there's a bypass as far as I know. Think all I can do is keep monitoring it and get the plumber back in if I can see a pattern.
Having tried the Drayton Wiser, I think it was better in all honesty. It had easier configuration to suit your needs. This Tado seems to be limited, like you can't adjust the booster unless I'm missing something? It just goes to max for half an hour. It was more difficult to add to routines with Alexa or my Sonoff hub, still not convinced by it and the returns window is closing...
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Always possible that the external bypass is faulty. I’ve seen this on new and old systems. The simple check is to feel the temperature of flow and return pipes either side of the bypass when the heating is on or off. The logic should give a clue. If the system is not for you, don’t miss a return window.
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Very good point! Many thanks, your help is very much appreciated :-)
I take it back on the Tado, spent a bit more time tinkering with it today, just the whole automation side. All set up perfectly now, just hope the pump behaves
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