Potterton Lynx 2 Combi boiler noises

[Steve]

Help, When boiler is on heater it makes, what I can only describe, as a boiling sound. This doesn't happen on water heating. Any suggestions? Steve

[Ed Sirett]

Diverter valve trouble. Stuck in DHW position.

[Steve]

Is it easy to get hold of & replace?

Steve

[Ed Sirett]

To confirm the heating should be nearly broken, as the flow to the rads is restricted.

Fairly pricey, although a service kit replacing the moving parts might be available.

If you have the service manual it should be straight forward. A good selection of quality adjustable wrenches are a much for this type of job. It involves both the mains water and primary side of of the boiler but no gas work.

[Steve]

Snip

No the heat to the rads is absolutely fine, just the noise when heating.

Cheers Steve

[Ed Sirett]

Would you describe the noises as 'kettling'? Have these noises started suddenly or have they been getting worse for some while?

[Steve]

Yes you could say "kettling" is an apt description. The noise nas seemed to develope over a period of time - days not weeks - however it has now quietened down a little. Very strange.

Steve

[Ed Sirett]

The design of the LYnx is a tube-in-tube heat exchanger. the gas heats the primary water, the DHW is in the inner tubes so is preheated.

The pump moves the primary water at all times the burner is on. In DHW mode the radiators are short circuited so the water moves quicker.

Do you have TRV's on all/most radiators? If so you might find that as the house heats up the primary water is slowing down and the kettling begins.

If the noise bothers you treating the primary water with Boiler Silencer which is a noise reduction gel may help a lot.

Also turning down the CH temperature may help if you do so without getting cold.

[Steve]

Thanks Ed

Please see my comments against yours.

Yes TRV's are fitted to all but two rads, one in the conservatory and the one in the upstairs airing cupboard.

What noise? It's totally died down as if it was never there - just a thought: last November we added some descaler to the rads, do you think that some scale broke off and was constricting the flow? I'm just wondering as one of the rads took longer to warm to the top than the others, I put it down to this one being farthest away from the boiler, but now the noise has stopped that rad gets warm as quickly as the others.

I'll leave that one for later - have you seen the forecast?

Cheers Steve