Circulator pump issues: airlocked?

[HammerandTongs]

I'd be really grateful for any help with this.

I recently moved into my flat, and when I turned on the boiler the central heating would run constantly regardless of the demand from the timer. The hot water worked normally.

In terms of setup there is a Potterton Profile 50 gas boiler supplying both the central heating and a hot water cylinder. CH & HW are both controlled by a timer and are set up as two parallel two-way valves rather than a 3 way valve. There is an expansion tank.

I could control the central heating to some extent obviously by closing the individual radiator valves, but it was less than ideal.

I found that the central heating valve and motor were seized and not operating, so I powered down and freed them up and lubricated them. Now they open and close as per the demand from the timer (which also fires up the boiler).

However, now no hot water seems to flow beyond the circulator pump (located before the CH/HW split). The circulator pump heats up (a lot!), but the pipes beyond are cold and there's no hot water or heat in the radiators.

I thought it could be an air-locked system, so I tried bleeding all the radiators (no air), the circulator pump (quite a lot of air and steam through the central screw before water) and a valve above the boiler (again quite a lot of air before water).

Problem is even after bleeding this air there's still no hot water beyond the circulator pump. The boiler still fires up (I've turned the dial on the boiler right down because otherwise it trips the overheat cutout after a while presumably because the hot water isn't going anywhere), but nothing else.

Could there still be air in the system? If so any ideas about getting it out? I've tried adjusting the setting on the circulator pump (goes from 1 to 3). Any other thoughts on what might be wrong/things to try?

Thanks in advance for any help with this.

Rob

 

[compheat]

Check to see if there's water in the feed and expansion tank

 

[HammerandTongs]

thanks for the input. I've tried opening the water hose valves to the pipe above the expansion tank, and the pressure valve next to it rises steadily until I close the valves. I haven't let it rise above about 2 bar, as it was my understanding that these things usually operate with pressures about the 1-1.5 bar mark.

There's what appears to be a release valve above it, which has a pipe leaving horizontally and then turning vertically upwards, and which lowers the pressure again.

Is there something different I should be doing with these?

 

[xr4x4]

thanks for the input. I've tried opening the water hose valves to the pipe above the expansion tank, and the pressure valve next to it rises steadily until I close the valves. I haven't let it rise above about 2 bar, as it was my understanding that these things usually operate with pressures about the 1-1.5 bar mark.

There's what appears to be a release valve above it, which has a pipe leaving horizontally and then turning vertically upwards, and which lowers the pressure again.

Is there something different I should be doing with these?

Eh?

Vented systems don't normally have a pressure gauge?

 

[HammerandTongs]

Sorry, I think I misunderstood re. feed and expansion tank. This is a fixed red cylinder, sealed and connected to the piping, with an input to the pipework directly above it via a plumbed in hose from the loft, with an adjacent pressure valve. The hose has two valves which are both normally in the closed position.