No advice forthcoming about flushing, so took a gamble and flushed the primary as above. A fair amount of black sludge was dislodged and I don't think I caused any damage.
Then fitted the new-style water-water HEx plus the new pipes that came with the kit. Also replaced the two temp sensors - the one on the main gas-water HEx had a cracked body and verdigris on the leads (faulty AAV in the past).
Fitting the w-w HEx was "fun" to put it mildly. That 8mm bolt on the primary flow adaptor is a swine! I found the best way to deal with it was to lubricate its threads slightly and work it in and out all the way a few times before fitting the adaptor, so that most of the turning can be done with your fingertips and only the last half turn or so with an open spanner (about 5 degrees at a time!). I found it needed 3 full turns, not 2 as stated in the MI.
The slight tilt of the HEx to the left seems odd, but seems to be correct as the EV wouldn't go back in otherwise!
But pleased to say that everything works perfectly now, so THANKS EVERYONE for your help.
The DHW flow rate and temperature are definitely improved, much quicker to run a proper, hot bath now.
If the fault recurs, I'll try what the good Boilerdoktor suggested.
Still have the rain-through-flue issue to resolve, but will be leaving that to somebody suitably qualified, who will also be doing the annual service.
C.
Then fitted the new-style water-water HEx plus the new pipes that came with the kit. Also replaced the two temp sensors - the one on the main gas-water HEx had a cracked body and verdigris on the leads (faulty AAV in the past).
Fitting the w-w HEx was "fun" to put it mildly. That 8mm bolt on the primary flow adaptor is a swine! I found the best way to deal with it was to lubricate its threads slightly and work it in and out all the way a few times before fitting the adaptor, so that most of the turning can be done with your fingertips and only the last half turn or so with an open spanner (about 5 degrees at a time!). I found it needed 3 full turns, not 2 as stated in the MI.
The slight tilt of the HEx to the left seems odd, but seems to be correct as the EV wouldn't go back in otherwise!
But pleased to say that everything works perfectly now, so THANKS EVERYONE for your help.
The DHW flow rate and temperature are definitely improved, much quicker to run a proper, hot bath now.If the fault recurs, I'll try what the good Boilerdoktor suggested.
Still have the rain-through-flue issue to resolve, but will be leaving that to somebody suitably qualified, who will also be doing the annual service.
C.
