Boiler "wails" with CH on, however no noise with D

[glider26]

Hi,

We moved into a house with a Minimiser SE boiler, open-vented, feed-and-expansion tank in the loft, boiler in the kitchen and water tank/pumps in an airing cupboard. I get woken up by a wailing sound coming from the boiler. I don't think it's the fan. Interestingly, we only get this sound when the boiler is used to for CH, not for DHW heating. Any guesses?

I don't know when the system was last serviced and if the rest of the house is anything to go by, my guess is that the previous owners, who were here for 5 years, never had it done. I have some scale inhibitor product on hand. I need to drain the system anyway because of 2 rad valves that need changing. Could it be limescale on the heat exchanger that is causing the noise? Why would we get noise with CH but none with DHW? I assumed it didn't make a difference at the boiler end but I'm obviously wrong.

Any advice much appreciated.

 

[Agile]

It sounds as if the flow through the boiler is lower on Ch and causing this noise.

If the boiler has a setting to reduce the CH power then this should be turned down. I dont remember one and it would be an engineer setting anyway.

You could check the pump speed, it should be on "2".

It does sound like kettling and if no other solution seems possible you could add X200 to the system and run first on HW reheat only for an hour or two.

Tony Glazier

 

[glider26]

Thanks! Both pumps (CH and DHW) are actually set to 3. I'll get some descaler as recommended then, right? How do I add this to the system? If I pour into the F&E tank, will it get to the boiler or just sit in the tank for ages? Do I need to drain the system?

 

[Agile]

Close one valve on each rad.

Tie up ball valve and take out most of the water in header tank until just covering the outlet. Tip in the X200.

Set on HW and get someone else to drain out about 4 litres from a drain cock while you control the ball valve to keep the water level just over the outlet.

The run for a few hours/days before you put on the rads again ( which would dilute the chemical ).

Tony