Glowworm Flexicom 30cx - Should I replace something as a precaution?

[DaveFix]

My Glowworm Flexicom 30cx was installed about 17 years ago.

After DHW has been used, the boiler continues to run for about 1 minute and sounds like it's still pumping water around (normal operating, not an issue).

However - the pumping sound has over recent years started to become a noisier chugging sound.

Surely it can't be the circulatory pump, I thought that was only used for central heating - so, does anyone know what this sound is likely to be?

OR ..if it ain't broke don't fix it... should I just ignore it?

 

[Gasguru]

The pump runs for both hot water & heating.

I'm not familiar with this model but you could try running the heating for 15 minutes and operating the hot tap a few times whilst it's on.

Sometimes air becomes trapped in the boiler over summer (and the internal auto air vent' is either blocked/screwed down or ineffective) and the firmware doesn't switch the diverter over during a pump overrun stage leading to a gradual buildup of air in the boiler when wholly used for hot water.

Alternatively, if the boiler hasn't been fully serviced for a while the heat exchanger sump, condensate trap or pipework could be partially blocked and the noise is the condensate sloshing about under the influence of the fan.

 

[DaveFix]

Thanks Gasguru, yes you're spot on there - the auto air vent is defective. I ordered a replacement which just arrived today.

I'm going to drain, flush, clean and renew the inhibitor while replacing the auto air vent.