unable to repressurise Worcester 28CDi after drain down

[croydoncorgi]

IIRC, after that point there is no further non-return valve, so in normal operation there will be hot boiler water there. Given it's a coolish spot, probably with a small 'dead leg' and eddies tending to drop particles in the 'branch' off the main flow, I suspect what you dug out was 'precipitated' magnetite, which forms hard, crusty deposits.
So chances are your system has no or insufficient corrosion inhibitor in it! This is also probably bad news for your secondary heat exchanger - as it's a combi.

 

[CorgiIOW]

As previous posters have said, there is not much to the filling loop itself.

As you look at the filling loop, the right hand side joins directly to the diverter valve, via a O ring seal. The diverter valve could be blocked, the other end connects , if i remember to the flow side of the boiler, again via O ring seal.

Really you need to dismantle the filling loop assembly, then you need to remove the W/W heat exchanger and clear that, this will enable you to remove / dismantle the D / Valve.

Its sounds as if your boiler is clogged with black debris, and needs a good clear out.

Be warned tho, if you do decide to strip the water sections, its worth investing in a complete O ring replacment pack, cos if you try to use the same O rings again, it will leak like a good un.

Its not the easiest boiler to strip,, but then practise makes perfect.

Good luck.

Dave.

 

[CorgiIOW]

Just to add, totally agree with croydoncorgi, if you do get round to removing the D / Valve at the back is or should be a small inlet water filter.

Although it could be blocked but i very much doubt it.

Reason been, water authority down here have been changing water meters and its caused no end of problems with clogged W/W heat exchangers and D / Valves.

Just a thought.

Dave.