On 13/06/2021 16:18, jkn wrote:

Hi All
thanks a lot for all the useful comments. I wasn't really expecting to get the nod
towards keeping the current cylinder, but it's useful to get more of an idea of the
various considerations. I do also appreciate that there will need to be some
replumbing...

Also thanks John Rumm as always for his wisdom, and for flagging the S Plan
possibility.

or even W plan (i.e. 3 port diversion valve rather than a mid position
one) has become more useful again with fast recovery cylinders that can
take the full output of the boiler.

It is partly a matter of location that it leading me to the System Boiler route - also
that (like Tim+) I don't like putting all my eggs in one basket, as it were. Having eyeballed

Yup cylinder (vented or unvented) with an immersion will give you options.

(although to be fair I have one in mine, and the only time ihas been
used was in the first few days after installation of the cylinder before
I had finished the boiler install and require replumb to convert from
vented to unvented etc)

the current setup again, one concern I have is what to do with the condensate drain.
Running a flue to the outside would be OK, but it is a long way to a drain or soil pipe etc.
Are there any other options here?

Yup there are a few - the main requirements for a condensate drain are
that it won't freeze and it won't mind the very slightly acidic
condensate. So taking and mixing it into an outflow from a sink or
washing machine that then goes through the wall in a larger pipe (say
40mm) is fine, or a dedicated pipe. The thing to avoid is taking the
21mm plastic pipe straight outside where it could freeze, or letting it
drip directly onto masonry where it could stain etc.

We have a 'French drain', for instance, and I wondered
if that could be brought in operation...

Yup a soakaway is fine - you are not talking about huge amounts of water
- a few L/hour at most usually.


FWIW one reason for doing this *now* is that the back boiler has starting making
'kettling' noises when it starts up. We've fairly recently set the controller to not put
the radiators on, but I wouldn't have thought that that would have caused any such
issues? It is looking to me that the heat exchanger is really sooted up - I actually

It might be just a lower load on it means its running hotter. Also scale
in the HEX can result in kettling. You could add some "Boiler Noise
Reducer", which normally calms it down a bit.

fitted a new thermocouple, and cleaned the jet out, a month or so ago, and it seemed
fine then. I'd quite like to fix/understand that even if we do finally sort out a
new boiler...

It probably also wants a good sweep out and clean - especially important
if it's not a balanced flue design.



--
Cheers,

John.

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