New Glowworm Ultracom 24cxi gurgles when starting

[dvrabel]

I have a newly installed Glowworm Ultracom 24cxi combination boiler.

When starting it makes a reasonably loud gurgling/trickling noise that eventually stops after maybe a minute or two. The noise is perhaps best described as similar to a washing machine filling and suggests to me that there's air in the system.

Is this sort of noise normal?

 

[gas4you]

Not normal. Check the pressure is around 1.2 bar when cold and that the auto air vent is loose in the boiler.

 

[dvrabel]

The small plastic cap on the top of the auto air vent was loose.

I bled all the radiators and the vent in the loft and the pressure dropped all the way to 0 bar, so I pressurized to around 1.2 bar. I did this twice and the problem seems much reduced.

Was there perhaps just too much air in the system for the auto air vent to handle?

 

[Gasguru]

Most boiler auto air vents don't actually vent off that much air. Normally it's best to run the boiler in heating mode and cycle the hot water on (for for several seconds), then off for several seconds allowing air to be sent to the rads where it can be manually bled. If there's a lot of air is safer to isolate the gas (ie reduce the chance of cooking the heat exchanger).