Loud bangs and surges in system

[donjuan1500]

Hi all. Hope you can help.

I have an open system with a top-up tank in the loft.

Every hour or so when the heating/water is on there is a surge and loud banging. Hot water surges up the overflow into the top-up tank and splashes everywhere.

I have tried slowing down the pump and also extending the overflow pipe to make it higher but it still happens.

Any ideas?

 

[ChrisR]

More info please - one or two motorised valves, etc? And what's the ******* boiler?!!!!

 

[donjuan1500]

Boiler: Baxi WM51/3RS
Pump: 1 Grundfos pump
Separate Sunvic control panel and thermostat.
There is a motorised Sunvic Unishare valve which diverts the flow of water to either water or heating systems (or both).

 

[donjuan1500]

Don't all rush at once!

 

[donjuan1500]

Further info:

It is a Y open vented system.

 

[donjuan1500]

1 Header tank for the hot water

2 Expansion tank for the Central heating

3 Air separator (if fitted)

4 Pump

5 Motorised valve

6 Indirect Cylinder

7 Boiler

8 & 9 Heating Flow & Return


Except it hasn't got an air separator

 

[DateMan]

You boiler Temperature is set too high, or maybe your thermostat has failed