On Tue, 14 Sep 2004 19:40:14 +0100, Andy Hall wrote:

On Tue, 14 Sep 2004 12:07:37 +0100, "IMM" wrote:


"Christian McArdle" wrote in message
x.net...
"Components:

A filling point.
A pressure relief valve and discharge pipe.
An expansion vessel
A pressure gauge"

"Automatic air vent" should be one of these points.

There is no requirement for an automatic air vent on a sealed pressurised
primary circuit. Sure, they're very useful and labour saving, but many
systems do not have them installed.

I know few. if any, systems that do not require an auto air vent above the
boiler on the flow pipe. In days gone by when there was no system boilers
with integral pressure vessels and all components had to be external, an
auto air-vent on the flow over the boiler was mandatory by all
manufacturers. You didn't think, you just put one in.


Where components are not present in the boiler, it is common to use a
sealed system kit, consisting of a manifold and the four items listed.
These don't have a vent.

For a vent to be useful near to a boiler implies that there is a
convenient place to install one and that the pipework reaches a high
point immediately above it.

If the pipework is at the bottom of the boiler, then it should have an
integral vent to be able to vent the heat exchanger.

Other than that, vents should obviously be at high points on the
system.

Indeed so, and they do not need to be automatic.
In my own home the highest points are the 4 upstairs radiators, the top of
the indirect cylinder coil and the top of the boiler's heat exchanger.
Only the latter has an auto vent. The others are manual.



--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at 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