Kettling noise in feed/expansion pipes

[nairb999]

I have a Potterton Prima 60F Central Heating system. Had problems with air in the system for a number of years. Changed the pump approx 4 months ago and since then get a kettling noise above the pump in the feed/expansion area after the system has been running for a couple of hours. I had been advised to check for blockages by placing a magnet on the suspected pipes and the magnet was attracted to the pipe in a number of spots

Added Sentinol X400 4 weeks ago and the system ran a lot quieter with minimal air getting into the system. So I thought the X400 had cleared the problem. After flushing the system clean - and it was thoroughly flushed through the system ran well for several hours before the kettling reappeared. The kettling noise reduces when raising the pump speed to 3.

The magnet is still attracted to the same areas of pipe and I think I will have to cut suspect areas. But the system is working really well with all 15 radiators getting to full heat within 20 mins and the kettling noise starts after 2/3 hours. So I am loathe to cut into system . Any thoughts ?

 

[Agile]

You need to either cutout the affexcted pipework or to risk using a stronger chemical.

I would isolate the radiators and add citric acid ( DS40 ) and circulate it warm around the hot water circuit for a couple of hours and then repeat that action with a little less acid before fulling flushing it out.

But be aware that adding acids to your system does carry a risk of leaks. I can make a judgement on that risk but I dont know if you should take that risk!

Tony

 

[nairb999]

The system does not have a hot water circuit. I have a seperate Gas fired water heater.