On Wed, 18 Oct 2006 10:51:15 +0100, Dave Plowman (News) wrote:

In article ,
Christian McArdle wrote:
A *properly* designed one won't pump over.

I rest my case.

Why? It's not difficult.

Clearly you have greater faith in the majority of people installing
these systems.

No - I read some of dribble's postings and realise there are charlatans
around. However, this is DIY and I installed my own. After taking advice.

It is a lot harder to muck up a pressurised system. You
are also much less likely to end up with a dangerous result, although
obviously any system can be dangerous if done too incompetently.

I'm not aware of the 'dangers' of an open system - apart from one
recently reported case, which was down to simple bodging on a number of
fronts including not having obvious faults fixed. But then some
sealed/pressurized systems - if this includes hot water - are known to be
dangerous hence the restrictions on who is allowed to install them and the
periodic safety checks needed.

There are bound to be problems with poorly installed pressurized
systems too come to that - leaks for one.

Well leaks are common to all plumbing.

Again only with poor workmanship.

I realise that sealed systems are the answer to some problems - mainly
space related - but they aren't the panacea some make them out to be.

I'd say that it's a point win to the sealed circuits. There is little to
choose on reliability stakes between the two arrangements if the
conventional system is correct. I.e the failed expansion vessels probably
balance against the stuck shut float valves, the over flowing header tanks
and the limescale plugs at the entrance to the circuit all of which are
problems that can and do occur on correctly installed conventional systems.

However the the failure modes for incorrect conventional systems are
multiple and severe.


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html
Gas Fitting Standards Docs he http://www.makewrite.demon.co.uk/GasFittingStandards