I have a Y-plan system with a Honeywell 4073 three port valve. The valve is several years old.
There is a bypass gate valve across the HW cylinder coil. It is cracked slightly open as it always has been.
The pump has always been on minimum speed and has not been changed.
Since starting to use the heating this year, I often get a loud bang from the 3 port valve when the boiler & pump stop once the room stat reaches temperature. This happens when the valve is in position A i.e. HW is satisfied.
The bang does not happen every time.
My understanding is that the valve should remain in the same position in this situation with port A remaining fully open and the motor stalled.
(Grey wire = ‘ON’, White wire = ‘OFF’).
After the bang, the lever remains free to move over its full range of travel which indicates it is still in the port A open position.
I have also noticed that the pump overrun switches on for a short time after quite a long delay after the boiler has switched off (I would guess after a couple of minutes).
The system was cleaned using Sentinel X400 a few weeks ago. It was left in for a couple of weeks then drained and refilled with water. After running the pump for a while to help flush the system, it was drained again. 1.5L Fernox MB1 inhibitor was added plus 500ml of Sentinel X200 boiler noise reducer.
All the rads and the cylinder coil have been bled several times.
Any idea why I am getting this noise from the valve?
There is a bypass gate valve across the HW cylinder coil. It is cracked slightly open as it always has been.
The pump has always been on minimum speed and has not been changed.
Since starting to use the heating this year, I often get a loud bang from the 3 port valve when the boiler & pump stop once the room stat reaches temperature. This happens when the valve is in position A i.e. HW is satisfied.
The bang does not happen every time.
My understanding is that the valve should remain in the same position in this situation with port A remaining fully open and the motor stalled.
(Grey wire = ‘ON’, White wire = ‘OFF’).
After the bang, the lever remains free to move over its full range of travel which indicates it is still in the port A open position.
I have also noticed that the pump overrun switches on for a short time after quite a long delay after the boiler has switched off (I would guess after a couple of minutes).
The system was cleaned using Sentinel X400 a few weeks ago. It was left in for a couple of weeks then drained and refilled with water. After running the pump for a while to help flush the system, it was drained again. 1.5L Fernox MB1 inhibitor was added plus 500ml of Sentinel X200 boiler noise reducer.
All the rads and the cylinder coil have been bled several times.
Any idea why I am getting this noise from the valve?
