DIYbanter - View Single Post - DIY Combi boiler and central heating system

Mr Fizzion wrote:
On 23 Jan 2006 12:28:27 -0800, wrote:

Hi,

I am thinking of fitting my own Combi boiler and central heating
system(then a gas fitter connecting the gas).
Can anybody give me a simple overall description of how to do this.

1.We are thinking of fitting the new combi boiler in the bathroom,do i
simply connect a mains cold water supply to the boiler and tap in to
our existing hot water pipes with the DHW connection.
Pretty much though because your old system probably worked at low
pressure, you may need to change some of the pipe fittings and taps.

Check that the bathroom is big enough. You cannot put a boiler in Zone
1, and you may have to fit it in zone 3. Check the installation manual
for this.

2.What size plastic pipes do you run for the central heating part,do
these reduce down at any point.
22mm. Tee off to the radiators with 15mm or 10 mm.

3.Do plastic pipes need lagging or are they thermally efficient.
Lagging is still necessary under a suspended ground floor, in the loft
or outside.

4.I understand the need for a filling loop,what other stop valves or
relief valves are needed.
A liberal sprinkling of lever ball valves is useful for isolating
parts of the system. Don't get cheap ones - they leak. Don't get gate
valves - they seize.

You might need an extra expansion vessel depending on the size of your
system. You need a drain point somewhere near the lowest point in the
system with some sort of valve on it. An inline filter on the return
from the central heating is advisable.

5.Do all combi boilers have a pump internally or do some not.
As far as I know they all have a pump internally.

6.We are not planning on fitting radiators initially,can just the DHW
system be used then radiators connected afterwards.
Not very likely. You need some kind of bypass on the radiator circuit.
You could probably fit just one radiator initially.

7.Will any of our existing water pipes(hot/cold)to taps throughout our
house need replacing.
Joints that were previously under low pressure may need replacing.
Compression joints may just need tightening. If the toilet was fed
from a gravity system the ball valve may well fail and water will
constantly drip out through the overflow.

8.Do combi boilers come with installation/startup instructions for the
initial setup.
Yes.

9.After the gas fitter has connected the boiler,should he set the
boiler up and check the hot water system or is this left to yourself.
He will do it! He needs to check the pressure drop etc. when the
boiler is running.

From other posts i have read about DIY central heating it seems quite
possible with some DIY experience to undertake this job,i just need to
know of anything specific that should be done when fitting a system.
Yes it's quite possible...I did it with minimal experience. My best
advice would be to download the installation manual for the boiler you
intend to fit from the manufacturers website and read it from start to
finish before you do anything.