Strange air noise and “whooshing” near pump in an otherwise efficient central heating system

[Plumbingnovice101]

Hi all

I have a standard Y plan heating system with a Potterton Suprima 50 in the kitchen, 3-port valve, Myson Compact CP53 pump, and hot water tank in the airing cupboard, then an F&E tank in the loft; with a combined feed and vent.

The heating system is simple and generally performs well, with all rads getting hot and Hive suggests the house heats up quickly. Considering its age, it does seem fairly efficient.

However, ever since we moved in we have had a “whooshing” and thudding noise occur that is quite loud every time the CH pump starts up. After about 30 secs to 1 minute the air noise has completely stopped and the system is fairly quiet and normal.

For ages I have ignored this on the basis the system was working fine but the noise is now waking up our 2yo as her bedroom is opposite the airing cupboard.

I have stood near the pump and turned the heating on and the noise seems to be occurring above the pump (the pump direction is downwards towards the 3-port valve) and is therefore seemingly sucking air in from above.

I am confused by this as my understanding of a combined F&V is that air cannot (easily) get in as the water level is above the combined F&V pipe.

Tonight I have sat in the loft and felt the pipes leading up to the F&E tank get warm but nothing drastic, and the final “rise” up to the F&E tank stays cold. The water level in the F&E tank doesn’t seem to change.

I have attached pictures of the condition of the F&E water, the combined F&V pipe, the pump, and the start of the combined F&V pipe leading up to the F&E tank.

Is my assessment of an air lock correct and if so, what is the best way forward please?

Any help much appreciated!

Cheers
Mike

 

[cross thread]

Check the “air jack “ with a magnet , they tend to start blocking,if the magnet sticks it will need cutting out and replacing./ cleaning

 

[Plumbingnovice101]

Check the “air jack “ with a magnet , they tend to start blocking,if the magnet sticks it will need cutting out and replacing./ cleaning

Thank you, appreciate your response. I had read elsewhere that this may be the issue.

But I was a bit skeptical as the hot water does seem to still vent into the loft pipes as the pipes do get a little warm up there. Could there still be a blockage if this happens?

 

[Johntheo5]

Where exactly is the combined Vent&cold feed, does the vent from the boiler outlet (flow) pass up and over the F&E cistern with the cold feed teed into it and does this then feed into the inlet (suction) side of the pump?

 

[Plumbingnovice101]

Check the “air jack “ with a magnet , they tend to start blocking,if the magnet sticks it will need cutting out and replacing./ cleaning

Just to add, I’ve checked the air jack with a fridge magnet this morning (strong enough?!) and it didn’t stick to anything!

Where exactly is the combined Vent&cold feed, does the vent from the boiler outlet (flow) pass up and over the F&E cistern with the cold feed teed into it and does this then feed into the inlet (suction) side of the pump?

Hi John, thanks for your help; the boiler flow pipe comes up into the airing cupboard from the floor and splits into the “air jack” in my picture, then goes back down, into the pump, then into the 3-port valve… the air jack is at about 7ft from the bottom of the airing cupboard.

Above the air jack, it goes up into the loft, runs flat across the loft floor, then up again into the F&E tank.

The F&E tank itself is situated above and to the right of the pump, about 3ft to the right, next to the loft hatch.

 

[Johntheo5]

These Airjecs are famous/notorious for getting sludged up, is the pump running at maximum head on CC3 or whatever.

Is it installed (correctly?) like below.

 

[Plumbingnovice101]

These Airjecs are famous/notorious for getting sludged up, is the pump running at maximum head on CC3 or whatever.

Is it installed (correctly?) like below.

No it isn’t plumbed like that at all. But maybe because there’s no cold feed in situ? The boiler flow simply splits and goes into both inlets, then comes out of the other side on the outlet as a single pipe. It vents up as normal.

There’s a picture of it attached. The side you can see is the boiler flow, as you can see, it simply splits and goes into both inlets.

 

[Johntheo5]

Where's the cold feed teed into the system?

 

[Plumbingnovice101]

Where's the cold feed teed into the system?

Do you mean from the F&E tank? It’s a combined feed and vent so there isn’t one. The vent is also the feed.

The only other cold feed is on the domestic side.

 

[Plumbingnovice101]

Where's the cold feed teed into the system?

Looking at the instructions you sent, I think it should have been plumbed like no. 5 instead.

Do you agree?

 

[Johntheo5]

Looking at the instructions you sent, I think it should have been plumbed like no. 5 instead.

Do you agree?

Where is the cold feed teed in on this no5 system?,
You might be better off cutting out the aerjec and just carrying the pipe on up, I have a 52 year old "combined" vent and cold feed but the vent is carried on up and over the F&E cistern, don't know if it makes any difference or not (the vent) but some of my rads are over 40 years old.

 

[Plumbingnovice101]

Where is the cold feed teed in on this no5 system?,
You might be better off cutting out the aerjec and just carrying the pipe on up, I have a 52 year old "combined" vent and cold feed but the vent is carried on up and over the F&E cistern, don't know if it makes any difference or not (the vent) but some of my rads are over 40 years old.

Thanks for all your help!

I think the confusion is, this combined feed and vent is a concept British Gas started doing about 20 years ago. It’s created by having a 22mm pipe from the bottom of the F&E tank, allowing for the same pipe to feed the system and also vent any air out.

It has its pros and cons, for example it’s slow to drain the system, but the main advantage is that there is no pipe above the water level in the header tank, so in theory… no air is meant to get in!

What I suspect has happened here is that when the system has been drained down in the past, air has got in and now can’t escape (as it’s been plumbed incorrectly).

On the basis there is no separate cold feed, I think it’s fair to assume I just need the “aeration” setup only… and therefore it has been plumbed incorrectly!

 

[andyr123]

hi - have you got an AAV anywhere in the system pipework at all? - if you have you can try opening up black/red plastic cap and see if any air releases?

 

[Plumbingnovice101]

hi - have you got an AAV anywhere in the system pipework at all? - if you have you can try opening up black/red plastic cap and see if any air releases?

View attachment 362452

Sadly not Andy, can’t see any anywhere. The only option to bleed the system is at the rads… which are all bled!

 

[andyr123]

is the F&E vent pipe going over the header tank in the loft on your system like this?