Matt Beard wrote:

I guess that I still regard sealed systems as "newfangled" and best
avoided unless needs must. (OMG am I starting to get old already?)

;-) can't answer that!

More practically, there are three problems for me with this:

1) The slightly higher pressures makes leaks a little more likely (but
then if my soldering is up to spec...)

Well if your mains cold water does not leak, then you could say there is
no reason for your heating to either. There is a chance if you were
upgrading an existing system that you would need to replace some old
radiator valves if they weep after conversion. There is also the
possibility that any radiators that are on their last legs would give up
also - but in which case it is only a matter of time anyway.

Since you are talking about a new install (which no doubt will be
protected by inhibitor from the start and be using new components and
valves etc), it does not sound like it will be a problem. Look at the
bright side - if it does leak at least there is a limit to how much
water can come out!

2) Space is very limited where the boiler is going (only just enough
room for the boiler).

A sealed system need not take more space round the boiler. ("system"
boilers will include all the required components for a sealed system
inside their case anyway).

3) There seems to be close to nothing useful available on how to design
a sealed systems, whereas there is quite a lot of info kicking around
for vented systems. (Although maybe not quite enough for my uses,
otherwise I wouldn't have to ask questions here!). It seems that the
general attitude seems to be "vented central heating? no problem, this
is how you do it... sealed system? nah, you need to get a professional
in for that"

One of the traps you may be falling into is that most sealed system
installs they are actually far simpler than conventional vented ones.
Hence there is less information available since there is less you need
to know.

Have you read Ed's FAQ?

http://www.makewrite.demon.co.uk/SealedCH.html

Many folks will start with a system boiler. This includes the pump,
expansion vessel, overheat protection, and possibly even the filling
loop. To turn this into a complete heating system you just add pipes,
radiators, and a room thermostat.

If you want stored water heated as well, then you would need a cylinder,
a stat (and/or flow switches if you want to get clever!), and suitable
valve arrangements just as you would on a vented system.

--
Cheers,

John.

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