Unable to top up pressure on Alpha CD35C Combi Boiler

[Steve Shad]

The central heating circuit is slightly low on pressure so I tried to top it up with the built in filling loop. Nothing happens. No mains water gets pushed into the heating return pipe. I disconnected the filling loop on the heating side to test the double-check valve, and mains water comes out, no problem. With the filling loop still disconnected at the heating return pipe end, I opened the isolation valve expecting heating circuit water to come out. It doesn't. I removed this valve to see if the ball is moving and the valve opening correctly. There is no problem with the valve and even then, no water leaks out from the heating circuit.

On this boiler the filling loop heating-side isolation valve is joined directly to a "Heating return valve". This valve takes the copper pipe from the radiator returns on one side, and turns 90 degrees up through the boiler casing. The connector for the filling loop isolation valve is on the side of this. Could it be that this valve is blocked or broken ? I called up Alpha to see if it is a known problem with these valves, but was told they do not normally give any issues.

The heating is working normally despite the slightly low pressure, so the return from radiators into the boiler is free-flowing through this valve.

Do I need to call a plumber to replace this valve, or could it be something else ?

Thanks for any help,

Steve (DIY Plumber)

 

[Gary.thornton]

Is the boiler in a high up place? Like upstairs/loft? Sometimes there just isn't enough water pressure to get over 1 bar. Had it myself on a few boilers.

 

[Steve Shad]

Is the boiler in a high up place? Like upstairs/loft? Sometimes there just isn't enough water pressure to get over 1 bar. Had it myself on a few boilers.

No, it is ground floor and has never given top up problems before, though it is a while since I last had to do it.

 

[ShaunCorbs]

I’ve had a few lately that are either blocked or have a stuck non return valve

 

[Steve Shad]

This problem has been solved. The feed point from the filling loop into the heating return pipe was blocked. Now cleaned out, re-pressurised and working. Thanks for the inmputs.