New MA1 Oscillating

19 Oct 2021
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United Kingdom
I have a 22 year old oil fired standard non-pressurised system with Drayton MA1 3 way valve and 'Lifestyle' connection system. A couple of years ago I replaced the old controller and some of the rad TRVs with the "Wiser" controller.

Recently this started banging when going from mid position to heating so after reading similar posts on this forum I replaced the original valve and actuator with a like-for-like MA1 from ToolStation. (The actuator showed some wear in the turning plate so I thought play here could be contributory). I also drained and flushed the system at the same time.

All well and good for a week and then the valve started to loudly oscillate or flutter as it was going from mid position to heating. If I remove the actuator and turn the valve by hand I have to hold it hard against the endstop to stop the oscillation. It will do this even with all rads calling for heat and with the pump on the lowest setting so probably not a back-pressure problem. I have re-bled the system. The actuator is working fine and does hold the valve in position when fully at the "H" position. It is just the second or so transition when the oscillation occurs and reverberates around the whole system.

Nothing else has changed in the system so I'm suspecting an early failure of the valve itself. Has anyone here seen this as a mode of failure of these valves?
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