Central Heating banging after bleeding radiators?

geordie_ben

The other week I went round with a radiator key and bled them to make sure there was no air as some weren't getting hot all the way up

That's sorted now

But, during the night the radiators and pipes are very noisy, banging, popping, clanging etc.

It's only started since I bled them.

I've tried turning the central heating off for a few hours, then checking for air again but they're all still full with no air at all.

Any ideaa?

Crinkmeister

Combi or conventional system with header tank?

geordie_ben

Combi boiler

Crinkmeister

After you bled air out, did you have to top up system? What's the pressure gauge reading?

geordie_ben

I didn't top the system up no, should I have?

The pressure is about 1.75

Seronera

Crinklmeister is quite correct of course. I'd just ask additionally if you bled the radiators with the system turned on or off. It should be off when you vent rads. So repressurise to 1 bar when the system is cold, set the system going, then check radiators again. If not hot at the top, turn system off, vent the radiator just until water appears, tighten vent and top up pressure again at boiler.

That should sort it out.

geordie_ben

Bled whilst off. Repressured now at About 1.75

Seronera

Apart from the noise does the system work OK? How hot are the radiators? Banging noises can occur if you are putting too much heat into the system. Do all the radiators get uniformly hot reasonably quickly. Did you vent the pump on the combi? Is the Automatic Air Valve on the combi open and working.

All I can really think is that the system is just a bit out of kilter somewhere and just needs working through methodically to get it operating right again. I know that's not a lot of help, but without being on site its difficult to be more specific.

geordie_ben

Yeah the system works fine, all radiators heat up pretty fast, and are hot top to bottom

I'll reduce the heat on the boiler and see if that helps

I'm not sure how to vent the pump, so no. And I'm not sure what the AAV is either

geordie_ben

If it helps it's a Baxi Combi 105 HE

rockin_plumber

If this is at night when you are in bed and all is quiet you could be hearing the radiators and pipework expanding as it heats up.


Pipes are tight in notches and not insulated...
Or pass through a hole too tight...
Or radiators without the plastic inserts on the brackets...


These are all things that will make a noise as the system is heating up.


The fact you mentioned it only started when you bled them may make this theory wrong...
Unless a lot of the radiators you bled weren't working until you did so????