AIR in central heating system

[TADERZ]

About 4 years ago we had some person come to extend a radiator to another place in the room, ever since then we have had air buildup in the system, we have to bleed the radiators every day. We had plumbers to come and see the problem none of them knew what was going on, one of them told us that the previous owner of the house had changed the system from a gravity fed system to a pump system.

We know that there is sludge in the system but we are 100% sure that it cannot be this because all pipes are filled with air and sludge cannot create such vast quantities of air. I would flush the system but if i do this and it doesn't work then it will be a waste of money. I have tried to do the hydrogen test with a mach and nothing.

 

[Doggit]

Did you have a problem before the rad was added, and how soon afterwards did the problem start to occur

 

[TADERZ]

No there was no problem before we added the new rad the problem started about 1 or 2 weeks from it

 

[slippyr4]

Pumping over?

 

[TADERZ]

i have turned the pump down from three to two but i can still hear air getting draged in

 

[Doggit]

Did he drain the complete system down when he fitted the rad, or just isolated the necessary pipework.

What's the boiler, and the setup. If it was changed from a gravity fed system to a pumped system, when was this done. Is there still a header tank, and have you seen the water been pumped into the header tank when it over heats, or when you hear the air being dragged in.

It's possible that the sludge has built up in the system, and it'd forcing the water round the wrong way. Do all the rads get hot, both at the top, and the bottom.

You don't need to do a power flush yet, but you could start by taking the rads off and flushing them out, and then putting in inhibitor.

 

[TADERZ]

He completely drained, it he also changed two other radiators to towel radiators and extended them to different parts of the room
The boiler is a ideal mexico 100 open vented system and i don't know when this was changed as the previous owners had done this
Yes there is a header tank
No i have never seen the water being pumped in
There is is rad downstairs that takes a while to get hot and most of the radiators get cold from the bottom and hot from the top

 

[Doggit]

What's happening when you hear air getting sucked into the system, and where do you hear it from. You may not have seen water getting pumped into the header tank, but if the water in there is warm, then you've got an over pump situation.
Do you know if the plumber added inhibitor to the system when he did the work - it almost sounds as though he didn't.

From you're description, you've definitely got sludge in the system, so start by adding fernox X400 to the system for a couple of weeks, then remove each rad and flush it though, and then add inhibitor, then see what happens.