Blocked filling cock Vokera Linea 28?

[kjmcdow]

Just took me over 4 hours to refill central heating system. I am thinking that filling cock on the boiler side of filling loop is only allowing restricted flow. Reason for thinking this is that flow to filling cock seems to be fine, as judged by disconnecting fill loop with mains cock open, and that after pressurising system the opening of the filling cock (with fill loop disconnected) does not result in flood of escaping water, only a few drips. The latter would seem a pretty good indication that the fill cock is blocked. The filling cock in this system is the one that screws into the main heating cock.

What do you guys think? Any other test I could do?

In case you are wondering, drained system to unblock the pipe to the expansion tank. The pipe was full of crud, fortunately I had a wooden kebab stick to hand. I think the crud was deposited before the system had been flushed and a magnaclean filter installed. Domestic hot water heat exchanger is as clean as whistle. No other niggles apart from a rattle, presumably the diverter value. Not bad for this boiler since is now 14 years old.

 

[Terrywookfit]

A common problem. Heating flow cock gets blocked internally.
There are 2 set ups NRV on Htg cock and NRV on cold valve.
Replace Htg flow cock or cut a filling loop in below!!

 

[Madrab]

As Terry mentions, usually there is a double check valve on the heating inlet side (long silver/bronze valve with a small bolt in the middle of it), it may be faulty and needs replaced.

 

[kjmcdow]

Thanks. The problem seems to have been with the main heating cock or I have just benefited from good luck. Just tested the fill loop, same problem as I reported. I then decided to check that the two main heating cocks could be turned off before thinking about isolating the boiler and disconnecting the filling cock to check that the flow through it was good. The main heating cock to which the filling cock is attached was stiff but by applying a bit of pressure both ways was able to get it through 90 degrees. Before getting in the toolbox, I thought I would retest the flow through the fill loop - don't ask me why, forever optimistic. I was met by the sound of water gushing through the loop. Perhaps a bit of crud in the main heating cock was restricting flow from the filling cock and loop?