Grant Vortex 26e

[MickyP10]

I get dramatic 'bloop-bloop' noises when DHW is on, then when heating's on you can hear air being dissipated through rads, then I bleed them until next time... System is inhibited (X100) and I added a couple of litres of X200 in system in case it was limescale (although we are in a soft water area). No difference, although maybe it needs longer to work or another dose. I can bleed the DHW until blue in the face via the manual and three auto vents but it starts again when DHW is getting close to target temp.

When I drained boiler via filling loop (the drain plug is blocked) to replace a flow valve, the water was quite dirty. So I'm thinking there's a layer of sludge at base of boiler and it's heating up globules, or rust particles, and they rising to the top, making the bubbling noise. Does this seem likely?

As mentioned, I can't drain the boiler with it's proper valve but I could drain it fully with the filling loop, refill, drain again, until clear, etc. If that improved things I'd re-inhibit the system. Any thoughts or other suggestions, please?

 

[Exedon]

Yours is one of the older Grant combi's as it got the 3 dreadful auto air vents on.
We now swap them for manual air valves.
The combi's can be tricky to clear of air and every time you drain boiler your back to square one.
If the water in boiler if dirty it's the same in rest of system .
I would add x400 run for few days fully drain down then keep flushing system till clean.
Adding a system filter would be useful Grants own mag 1 is a decent bit of kit.
I would also be checking boiler temperature when close to dhw target temperature.
That's controlled by thermistors in heat store.
Also check dhw pump we have changed a few on older combi's.