ideal classic RS250 kettling

ok had a new unvented tank fitted and system changed from gravity to fully pumped.

initially the plumber connected to the original gravity connections on the boiler and got the flow and return the wrong way resulting in trapped air, probably in the heat exchanger.

anyway that's been sorted, they connected to the fully pumped flow and return connections that they capped off originally and I don't have the trickling bubbling noises. what I do have is kettling still.

so ive tried x800 for about 18 hours, put it through each rad one at a time with the pump on high then left it standing in the system overnight. put heating on for 1 hour in the morning emptied refilled run for another hour, emptied refilled. then I added x100 and x200.

to be honest looking at the water coming out I don't think its a sludge issue, plus my rads get toasty now the boiler is flowing the right way round. what im thinking is maybe because the boiler probably didn't have a full heat eachanger for about 3 weeks its scaled up really bad. if im patient do you guys think the x200 will do its thing? should I put another tub in, as ive actually got 12 rads, but some are tiny and only 1 is a tall double and 2 are short?

im wondering about draining down and adding the x200 directly to the heat exchanger or would vinegar work better?

p.s. the plumber recons its knackered and needs replacing, hmm really. must want to quote me for a nice new boiler after doing such a good job on the unvented.

 

ive tried x200. is f2 better?

 

ive done some temp monitoring of the flow temps with the return differential:

ok pump on setting 3

system had been on an hour about 2 hours earlier.

0 min 31 diff 6
5 min 36 diff 8
7 min kettling
10 min 41 diff 9
15 min 45 diff 9
20 min 49 diff 9-10
25 min 51 diff 8
30 min 58 diff 12
35 min 62 diff 12-13
40 min 64 diff 11
boiler stat trip at about 65
45 min 63 diff 10
boiler stat trip at 69
50 min 67 diff 10
55 min 69 diff 14

 

ok had some time to run the system up tonight.

pump setting 2:

0min 22 flow pump running boiler off diff 0
1min boiler on 1min later boiler making low hissing sound

5min 34 diff 9
7min kettling
10min 38 diff 9-10
15min 43 diff 10
20min 46 diff 10
25min 50 diff 11
30min 53 diff 12
35min 57 diff 13
40min 62 diff 14
45min 67 diff 16
50min 71 diff 17-18
last reading just before timer turned off, the boiler stat was about to trip also, roughly 90secs after the 50min reading 73 flow diff 19.

so it seems the higher the flow temp goes the bigger the differential.