Rumbling / banging noise when hot water or/and central heating on

[greg161181]

Hello, everytime hot water or central heating program comes on i hear a loud rumbling / banging noise and it will continue intermittently until program finishes. i have noticed the flame icon on boiler display intermittently goes out and comes back on. when flame icon reappears the noise can be heard. it is very loud and wakes us up in the morning when hot water program comes on. i have a glowworm flexicom 12hx condensing boiler which was serviced back in february. i have bled all the radiators in the house. any ideas what the issue could be? thank you

 

[ShaunCorbs]

First thing to check is the pump pumping / circulating

Do you know how old the pump is ?

 

[greg161181]

both hot water and central heating working fine. not sure how old. only moved in last year to house.

 

[SimonG]

Sounds like a circulation issue.

 

[SimonG]

Sounds like a circulation issue.

 

[ShaunCorbs]

Do you know if it's an open vented system (f and e tank a little on in the loft of above cylinder)

Or a sealed system ( red expansion vessel)

 

[Chuck]

I suspect from your description that the boiler is 'short cycling' and and the banging noise you hear is your heating pipes expanding and contracting.

Short-cycling occurs when the minimum heat the boiler can produce significantly exceeds the dissipation rate of the system it is feeding.

A common cause is TRVs (thermostatic radiator valves) being set to a lower temperature than the main thermostat.

On hot water systems it occurs when the flow temperature to the cylinder is too close to the cylinder thermostat temperature. The HW thermostat should operate at 60°C and the flow temperature needs to be at least 65°C, ideally higher if it can be set independently of the CH flow temperature, or the cylinder won't absorb heat fast enough for the boiler.

 

[greg161181]

Thanks Guys for your help. I will take a further look.

 

[greg161181]

Do you know if it's an open vented system (f and e tank a little on in the loft of above cylinder)

Or a sealed system ( red expansion vessel)

There is a small tank in loft so I assume its a open vented system.

 

[ShaunCorbs]

There is a small tank in loft so I assume its a open vented system.

When you air a rad can you hear this filling (might take a bit of water out to hear this)