Noisy CH pipework

[halton1957]

In spring we had a problem with banging/clattering around the air separator/cold water inlet pipework. Used some boiler noise reducer throughout the summer, the system was running daily for HW and no noises.
On starting the CH & HW to check it out before winter there was no improvement, noises were the same. They happen each morning 5 mins after start up and last up to 3 mins, after which the system runs perfectly and silently till next morning.
20yr old system is microbore, Gloworm fuel saver. Feed/expansion tank in loft. Grundfoss variable pump. 3 way honeywell valve. Myson air sep. Always had inhibitor in system. All rads heat up well and HW is good.
No desire to update system if at all possible, just can't live with waking the neighbourhood at 6.30 every morning.
I'm not a plumber but this seems like a water expansion problem to me, is there likely to be crud/scale around the myson aerjec? That's where the problem seems to centre, followed by clattering/banging up the FE pipe and air release pipe. The noises are really loud and I don't think it's pipework expansion. There are also occasionally whooshing/squealing noises.
Any suggestions will be very gratefully received. BB

 

[ScottishGasMan]

Clattering and banging will be air bubbles expanding and boilering in the boiler due to low circulation, which will bubble up and vent off via the air sep. Which is why your hearing noise there.

However the Air Seperators appear to be a problem area for blockages. Would be worth draining down and cutting it out for a look at and possibly doing away with it.

Other thing could be the pump its self sticking at first run in the morning, however you would be getting this whether it was heating or hot water and would most likley have suffered it though summer.

 

[halton1957]

Thanks for your reply, but why might the circulation be low now but not through summer? Surely it would be much less just going round the tank coil? BB

 

[ScottishGasMan]

Are you running the HW at the same time as the CH in the mornings where it bangs? In which case, you are right, you should still be getting at least the normal circulation through the cylinder that you have had up till now regardless of the CH circulation.

Could be air getting trapped in the CH pipework getting into pump stopping flow, overheating boiler which will boil a little water causing baning squeeling whooshing and once the air has moved out then circualtion would return to normal.

Still, first place to look would be the air seperator,

 

[halton1957]

Thanks again, yes I am running both in the mornings. I guess the only way to be sure is to cut out the air sep and it's pipework. I guess a plumber is called for though, I have a gas torch etc but I don't have the confidence to use it in the confines of airing cupboard close to the ceiling.
I could cut it out myself, but wouldn't ask someone else to sort it after I'd been at it!

 

[Nige F]

Before you cut out the airjec - run a magnet around it and see if there is any attraction caused by iron oxide deposits. I am about to fit an airjec to replace a conventional cf/vent setup here at home - there is an amount of oxide deposited in the feed/vent area which is common in old systems. Your Fuelsaver boiler is a low water content one like I used to fit back in the pre CORGI/Gas Safe days. I moved away from installing c/h after that and didn't do gas once one needed to be registered. As said the cold feed/vent area is a problem whether conventional or fitted with a de aerator. Keep posting and the forum will help you get to the bottom of the problem.

 

[halton1957]

Thanks for the tip Nige. A standard small horseshoe magnet did not stick, but a small piece of supermagnet stuck well to the aerjec and a little to pipes an inch or 2 from it.
6.30 today the system started perfectly, no noise at all. Been playing around with it this morning to reproduce the problem, but nothing.
I'll come back tomorrow with the latest. Thanks again.

 

[AL66]

If your magnet was the neodymium type they are incredibly powerful so you may well have loosened up chunks of magnetite - a magnetic filter in the boiler return would help to trap any bits now free to circulate before they block up the boiler heat exchanger.

 

[halton1957]

Just been trying the whole system, using roomstat and tankstat to call for heat. Each of them seemed to work correctly but I'm unsure about the position of the 3 port valve, the manual lever is in the mid position when HW only is on. Is that correct please?
Grasping at straws now I guess!

 

[Nige F]

I could get a fridge magnet to attract to (but not hold onto) the crudded area in my cf/vent. And I was getting hot water up in the f+e cistern too. I like airjecs but then I'm a biased old dinosaur

 

[halton1957]

This morning with HW and CH selected on via the programmer, when the roomstat cut out the boiler stopped even though tankstat was still calling for heat. When I switched the HW selector to off on programmer, the boiler cut in and the 3 port valve went to mid position.
Any ideas please?