Large volume of air in 1970's Baxi Bermuda Ch system. Help with fault finding please!

[poolz50]

Dear UKPF

I would really appreciate advice to try and problem-solve the fault with my very noisy, air filled central heating system. It bangs and thuds and there are long drawn out reverberating noises as air travels up to the highest rads.

I have bled all the radiators. I have to bleed two of them every day. In one day, they drop to 75% full – that much air has come into the system! It takes about 20 minutes each night to bleed the two ‘top’ rads to a point where they get fully hot and most importantly they stop making so much noise! Almost immediately after this you hear air working its way around the system again, from room to room!

This has been going on since I moved into the house~ 5 years ago as a tenant. However, I now own the house (yay) but this has now become my problem ! I have put good leak sealer and inhibitor in the system. There was zero difference. I have fitted Aladin automatic bleeding valves but this had no affect. They hissed a bit the first day but now do not clear the air at all.

What could be the problem? I have been assuming there was a leak somewhere hidden. I have inspected all pipes I can seem for wetness. The only place I can not is under our parquet floor which I cant pull up. I guess I will not see a air-intake leak, if there is such a thing?

So- the point of this post. Could it be anything else? I have read in some places that the central heating pump can drag air into the system. Can it? Could anyone advice what else I can try to diagnose the problem. To assist discussion I provide details for the system:


Boiler: Baxi Bermuda ~1971 behind the gas fire on the ground floor.
Storage Cylinder upstairs, directly above boiler.
Two water tanks in the loft, again, directly above. All the pipework runs up/down the chimney.
Grundfos Pump – set to 4 ( 2600 rpm)
9 radiators in 3-bed semi.
Pipework is mostly stainless steel with some copper work around the boiler.

The header tank is about the size of a microwave and the float/refill works well. The water is clear with a little bit of gunk in the bottom. I don’t think anything is getting dragged in.

When I bleed the radiators most of the time the water is clear. One of them is a little black water.

To Conclude

How can so much air be getting in?
Can it be the pump? ( I have put this on ‘2’ tonight to see if that helps)
Or something other than a leak?
What other logical steps can I do to problem solve?

I know its an old system and I must replace but I do not have the money and the noise is waking our 6 month old up !

Best wishes

Dan

p.S I asked a local plumber but he said it sounded like a leak and should be sorted by a new system. –I think he just wanted easy money .

 

[poolz50]

Re: Large volume of air in 1970's Baxi Bermuda Ch system. Help with fault finding ple

I am unsure if I have added the pictures I have taken. I hope so!

If not - they are in my dropbox :here

 

[thompsonbrown]

Re: Large volume of air in 1970's Baxi Bermuda Ch system. Help with fault finding ple

As your plumber has said it could be a leak but could also be other problems such as dragging air into the system. you could always turn off the mains cold water supply to the feed and expansion tank and monitor it over a few hours to see if the water level drops this would indicate what your plumber has said about a leak. Why not register and get the views of other plumbers.

 

[poolz50]

Re: Large volume of air in 1970's Baxi Bermuda Ch system. Help with fault finding ple

Hi - thompsonbrown, Thank you!

I thought I had registered. It says "welcome poolz50" at the top- which is my handle.

Do you seem me as a guest?

Thanks again

p50

 

[thompsonbrown]

Re: Large volume of air in 1970's Baxi Bermuda Ch system. Help with fault finding ple

Sorry thought it was your first post.
About your system I can offer some advice but is no way as good as a good plumber looking at your system.
1st your comment saying that your f&e tank in the loft looks clean would indicate to me that you may have a leak somewhere. A system installed in 1971 would usually have a bit more sludge build around inside the tank and the water would look really brown. Like I said before run and monitor your system with the water to your small tank in the loft isolated if its loosing water somewhere your water level in the tank will drop. If water level stays the same or even rises then your getting air drawn in from somewhere. First thing I would then try would be turning down your pump speed to see if rectifies your problem.

 

[gassafe]

Re: Large volume of air in 1970's Baxi Bermuda Ch system. Help with fault finding ple

Serious problem to have that much air in the system, either a leak under the floor or the cold feed & vent arrangement is wrong & drawing air in or pumping over & bringing lots of aireated water into the system... Expect some pinholed rads if this is the case!

 

[jtsplumbing]

Re: Large volume of air in 1970's Baxi Bermuda Ch system. Help with fault finding ple

1. knocking and banging, are you in a hard water area could be scale build up in boiler. 2. maybe faulty boiler stat causing boiler to over heat, 3. 1971 boiler have you thought about replacing it !!