vaillant turbomax 824?

[ardvark]

Builder accidently cut through rad. pipe, draining water from heating system. Pipework now repaired and boiler filled, but when I turn heating on, boiler fires up for 8 seconds and then switches off. Could it be an air lock? If so, how do I clear it. I have discovered a key underneath boiler that fits two valves. One allows water to build up pressure (i've been allowing 1-1.5 barr) don't know what the other valve does. Also discovered a plastic rotating knob underneath at back of boiler that lowers water pressure when turned. Have played with these but can't get boiler to stay on. Hot water is fine.

 

[chrishutt]

Could it be an air lock?

Very likely. You need to check pipework for high points that may need venting, as well as venting from radiators.

Does boiler operate OK on hot water (DHW) function? If so, it's not the boiler itself that's air locked. Check that the heating isolating valves below the boiler are open.

Press the "i" button on display to show status codes (e.g. S.07) - what is showing when the boiler tries to do the heating?

 

[ardvark]

Thanks for the info. (By the way, I'm not the builder who cut through the pipe, just the householder.) I will vent radiators but don't think there is any way for me to vent high points in pipework?? Also, how do I know when the heating isolating valves are in the open position?
P.S. The hot water side of system is working fine.

 

[ChrisR]

1)" Also discovered a plastic rotating knob underneath at back of boiler that lowers water pressure when turned. "

Aaargh, stoppit! That's a pressure relief valve which will open at 3 bar and let water out through the wall. Trubble is if they've passed water once they tend to keep leaking, so check the pipe outside for dripping.

The two valves the key fits are just opposite ends of the filling loop.

Find the isolating valves on the flow and return (22mm pipes). The valves are open if the screwdriver slot is in line with the pipe, not across it.