Banging when central heating on

[david1983uk]

Hi everyone.

When we have our heating on the system bangs ALOT!! It doesnt seem to just come from one place either but move around upstairs (we havent heard any banging from pipes downstairs)

I have tried to bleed the radiators but didnt seem to get air out of any before water. Is there something else I could try? Might I need to bleed the system so there isnt any air inside? Or could there be another problem?

Thanks in advance for your help

 

[45yearsagasman]

Is there something else I could try?

You could try giving more information about your boiler and system for starters.

 

[petertheplumber12]

A lot more info. when boiler starts firing up, after it has been on for a while, what the thermostat setting is. Etc Etc is a combi? or open vented?

 

[david1983uk]

Hi sorry
Its a combi boiler (glow worm). It only bangs when the heating it on. Normally starts about 20-30mins after heating comes on. The temperature is set at 17 or 18. It will continue to bang once heating cuts out after around 10 mins. The noise seems to be coming from pipes and not the boiler.
Hope that fills some of the gaps

 

[petertheplumber12]

The banging is probably water not being passed round the circuit fast enough. Are all the rads being heated or are some of them turned off? is water circulating to all rads, what heat output is the combi 24,28, 32, how many rads have you got. Is there at least one rad without a thermostatic valve preferably two?

 

[david1983uk]

Its a 24. All the heaters are on and we have 7 rads. There is 1 rad without a thermostatic valve. Its in the hall near the thermostat.
Hope that helps and thanks for your help

 

[petertheplumber12]

Do all the other 6 rads get hot at the same time and when banging starts are all the rads too hot to hold for more than 2 seconds. If less than two sec then turn boiler thermostat down until all rads can be held for 2 secs. When this is done does banging still happen?

 

[david1983uk]

We have just got in. Set thermostat to 16 and can hold heaters for 5-7 secs and banging has started

 

[petertheplumber12]

I believe your pump is not circulating the water fast enough, how hot is the flow pipe from the boiler within 1/2 meter of the boiler, and the return pipe is a lot cooler yes? Are the flow and return pipe 22mm or 15mm for all their visible length?

 

[david1983uk]

I believe your pump is not circulating the water fast enough, how hot is the flow pipe from the boiler within 1/2 meter of the boiler, and the return pipe is a lot cooler yes? Are the flow and return pipe 22mm or 15mm for all their visible length?

Hi Peter - Thank you for your help with this (internet has been broken) Im guessing I can find out which pipe is which from the manual ? The heating isnt on today so will turn it on later tonight and check the pipes. Would a broken pump also be to blame for a fall in pressure?

Thanks
David

 

[RWhites]

I believe your pump is not circulating the water fast enough, how hot is the flow pipe from the boiler within 1/2 meter of the boiler, and the return pipe is a lot cooler yes? Are the flow and return pipe 22mm or 15mm for all their visible length?

Hi Peter - Thank you for your help with this (internet has been broken) Im guessing I can find out which pipe is which from the manual ? The heating isnt on today so will turn it on later tonight and check the pipes. Would a broken pump also be to blame for a fall in pressure?

If the pump is broken, then there's your answer. But if all the rads are getting hot that suggests your pump is fine. The first thing I'd suggest is to check that the TRV-less radiator valves are open. Try to open each of them by one full turn (in order that you can put them back as they were if it doesn't work).

If you can't find your boiler manual, the flow pipe is the one that gets hot first coming straight out of the boiler when it switches on. It will probably be 22mm. The return pipe is the other 22mm that gets warm later (probably running parallel with the flow pipe).

The other (probably 22mm) copper pipe is the gas supply, then you've got the condensate drain (plastic) and a discharge pipe which I believe should be in 15mm copper.

Just a quick additional note, Peter suggested turning the boiler thermostat down, not the heating control thermostat (the one in the hallway). I'm not familiar with your boiler, but you're looking for a knob on the front next to a little picture of a small radiator - turn that down a little (following Peter's advice), and put the hallway thermostat back to where it was.

 

[david1983uk]

I believe your pump is not circulating the water fast enough, how hot is the flow pipe from the boiler within 1/2 meter of the boiler, and the return pipe is a lot cooler yes? Are the flow and return pipe 22mm or 15mm for all their visible length?

Hi Peter - Thank you for your help with this (internet has been broken) Im guessing I can find out which pipe is which from the manual ? The heating isnt on today so will turn it on later tonight and check the pipes. Would a broken pump also be to blame for a fall in pressure?

If the pump is broken, then there's your answer. But if all the rads are getting hot that suggests your pump is fine. The first thing I'd suggest is to check that the TRV-less radiator valves are open. Try to open each of them by one full turn (in order that you can put them back as they were if it doesn't work).

If you can't find your boiler manual, the flow pipe is the one that gets hot first coming straight out of the boiler when it switches on. It will probably be 22mm. The return pipe is the other 22mm that gets warm later (probably running parallel with the flow pipe).

The other (probably 22mm) copper pipe is the gas supply, then you've got the condensate drain (plastic) and a discharge pipe which I believe should be in 15mm copper.

Just a quick additional note, Peter suggested turning the boiler thermostat down, not the heating control thermostat (the one in the hallway). I'm not familiar with your boiler, but you're looking for a knob on the front next to a little picture of a small radiator - turn that down a little (following Peter's advice), and put the hallway thermostat back to where it was.

Thanks for this - The heater without a thermostat is in the hallway so might this be stopping water flowing upstairs? Guess I turn it to the left to open? Yep i know which one you mean on the boiler so will turn this down tonight. I guess the flow/return pipes should be around the same temperature once the heating has been on a while?

Might this also help the pressure issue ?
Thanks
David

 

[RWhites]

Thanks for this - The heater without a thermostat is in the hallway so might this be stopping water flowing upstairs? Guess I turn it to the left to open? Yep i know which one you mean on the boiler so will turn this down tonight. I guess the flow/return pipes should be around the same temperature once the heating has been on a while?

Might this also help the pressure issue ?
Thanks
David

Yes, anti-clockwise to open.
Flow and return should both be hot when heating has been on a while. Ideally, you should be able to tell one is hotter (flow) than the other (return), but they may both be too hot for that.

If the return does not get hot at all, that tells us something.

If you have individual radiators not getting hot (when they should) that also tells us something.

Why do you refer to a pressure issue? I don't see anything about it in this thread....

How many of your radiators are getting hot? How many are not? Where are they?

 

[gaspro1981]

Sounds like dodgy trv's

 

[david1983uk]

Ok thanks will give it a go tonight. All radiators get hot when the heating is on - some get colder quicker than others (these seem to be upstairs) We have 4 heaters downstairs one without a thermostat (in the hall) and 3 upstairs ( 2 bedrooms and bathroom)

The pressure thing is another issue - If we turn the heating off at 7am the pressure reads about 1.2-1.3 bar . 7 our of 10 days we come home at 6pm and its 0.6 bar. I was going to start another topic as wasnt sure if the 2 could be related.