Vaillant combi central heating keeps cutting out

[Liverpoollad]

Hi

I was wondering if someone can please help with the problem I am having with my vaillant turbo max plus 824e. Hot water is absolutely fine, but when the central heating comes on, the boiler cuts out and goes into some sort of cycle. Starts and then cuts out after a minute or so. The flow pipe is getting very warm and it's not staying on long enough for any of the rads to get warm enough.

Pretty sure it's not the diverter valve, as when the central heating mode kicks in, the central heating pipe is getting warm and not the hot water pipe. The pump is also getting really hot.

It looks like it's some sort of circulation problem, but all the radiators have been bled and all valves open. The pressure is steady at around 1bar. The pressure didn't increase very much when the central heating was working, maybe only a 1/4 bar.

The boiler is around 13 years old, and over the years has had most of the main parts changed, such as the diverter valve, pump, both heat exchangers.

Sorry for the long post...

 

[jackthom]

Has the heating worked OK at all in the past few weeks? Has any servicing been done since it was last working properly?

It could be the diverter valve only partially open, the pump on it's way out or something silly like the flow or return service valves on the boiler having been partly closed.

 

[Liverpoollad]

Thanks for replying, jackthom.

Heating has been working fine, no servicing recently. The pump is only a few months old, so I don't think it could be that.

The flow and return service valves are definitely open. The flow is pipe is getting hot a few meteres away from the boiler.

Could a diverter partially open cause this issue? I'll have a look, but if the flow pipe if getting hot, that would probably rule that out.

I'm still thinking its either a blockage or air lock, causing poor circulation. But not sure where to check for this.

 

[dilalio]

Why did it need a new pump only recently? Could be poor flow caused old pump to fail and new pump has suffered same fate!

Hose up a drain cock and purge a good slug of system water out to see if that encourages flow away from the boiler. Note state of water you let out which will give you an indication of what the rest might be like.

Don't forget to top back up via FL

 

[Liverpoollad]

The pump was changed because it was leaking badly. System water is clean, when I have bled the rads. I'll see if I can drain some water from the boiler itself, tomorrow morning.

 

[Agile]

The pump will leak when it has been damaged by dirt in the system!

Tony

 

[dilalio]

The pump will leak when it has been damaged by dirt in the system!

Tony

Exactly. You don't fix it if it ain't broke!

 

[dilalio]

The pump was changed because it was leaking badly. System water is clean, when I have bled the rads. I'll see if I can drain some water from the boiler itself, tomorrow morning.

System water at rad vents can be clean whilst the bottom centre of rads are solid with crud, especially at lowest points; even worse on drops ("U"'s).

Try and drain some off "away" from boiler if you have a draincock elsewhere... You want to try and encourage water to move downstream and hopefully any particles with it!

 

[Liverpoollad]

Have drained water from the boiler and from a few of drain cocks along the pipe circuit. Still no joy. Boiler is still cutting out after a minute or so. There is also a magnaClean fitted on the return. That has been checked and hardly anything collected on the magnet.

Anything else I can check guys?

Appreciate the help.

 

[jackthom]

Sorry but I have to ask are both valves on the Magnaclean definitely open.

 

[Liverpoollad]

Yes, both valves are open.