Banging in pipe when tado calls for heat

David1960_

I have the following devices: Smart thermostat RU1784819200. Wireless tempriture sensor SU3477353729. Internet bridge IB0312487168. The boiler is a Valiant ecotec 835 plus. The boiler is working fine and has been for a year now . The smart thermostat has replaced the old downstairs thermostat and controls the motorised valve on the central heating downstairs . Upstairs I have put the tempriture sensor to link with the smart thermostat to allow heating when it gets too cold upstairs. There was also an old thermostat upstairs controlling another motorised valve . This has been disabled and the motorised valve set manually open. As a whole the system has been working but there is an issue! When the smart thermostat calls for heat it opens up the motorised valve and asks the boiler for hot water. What happens is the a second after I hear the " click" on from the smart thermostat the bolier ignites and the is a " bang " in the pipes near the boiler! I suspect that the boiler is firing up before the motorised valve has time to open and this causes a brief pressure issue????? I did think this would be solved by leaving the upstairs motorised valve manually open to allow the pressure to be relived? Do you have any ideas on this please. I am wondering if it would be possible to leave both motorised valves manually open and then try to wire the smart thermostat directly to the boiler.If so I think I would need an additional piece of kit? received at boiler?

HandymanL23

Sounds like you are correct, a pressure spike is being created at the initiation of the pump run. Pipe banging is frequently due to its proximity to fixed objects which come into contact as the pipe becomes presurised and forced to straighten. If you can gain access to section of pipe where you pressume the noise to be comming from, wedge small offcuts of cloth to hold pipes away from each other and or joists, etc. Dependant upon the pipe material, copper / plastic, recommended pipe support centres need to be observed. As a test to confirm if the pressure spike is the source of the issue, adjusting the pump speed is possible on many manufacturers pumps. Check to see if speed adjustment is available on your pump and drop the speed if it is. I don't recommend that this speed change be made permanent as it should have been set correctly to provide the correct head pressure when the central heating poiler was initially installed. The noise should vary according to pump speed / pressure surge. In some systems, air locks can also produce noise in pipes, bleed the complete system, radiators and pipes, to discount this as a possible cause. Finally, try manually setting the diverter valve in central heating mode, prior to setting boiler demand. Some diverter valves can stick and jump open, causing a pressure spike in the central heating pipes.

David1960_

Wow . Thanks very much. That is really helpful. I'll try to see if I can reduce the speed of the pump to see if it's the pressure issue. I have the upstairs motorised valve set manually open but it did not help. I assume you mean the diverter valve in the boiler to set manually open ? Do you know if I can do this on a valiant ecotec 835 ? Fyi- the two motorised valves for the two heating zones are very close to the boiler. Don't think that helps.However leaving one set always manually open should rule out the valves not opening fast enough I believe. Thanks again!