Screeching noise from Vokera Mynute 28SE

[pantouphles]

Looks like a couple of other members have a similar issue* and a British Gas engineer is stumped so looking for some more suggestions ...

I have a Vokera Mynute 28SE with a cylinder in S plan configuration. The boiler fires, igniting the flames, then it makes a screeching sound for 10 to 20 seconds, the pressure rises then both the noise and pressure subside together. When the boiler is on supplying either CH or hot water there are no issues at all - radiators warm, pumps operating quietly etc.

The noise only seems to occur when the boiler has power but is off - ie there is no requirement for heat or hot water per the controls and all LEDs on the control box are off. It is also sensitive to the boiler thermostat setting, the higher the setting the more likely it is to happen. One night the boiler was firing every eight minutes, followed by the screech until I turned off the power to get some sleep.

The BG engineer heard the sound, agreed it was abnormal but couldn't find anything wrong. Any suggestions greatly appreciated.

* //www.diynot.com/forums/viewtopic.php?p=34233#34233 and
//www.diynot.com/forums/viewtopic.php?p=1952257#1952257

 

[45yearsagasman]

Difficult to be sure, but the symptoms you describe could be one of your zone valves, although the controls are saying off, the end switch on one of those valves is staying closed and firing the pump and boiler for a short time.