I need to replace my existing boiler with a new condensing boiler.
As I understand it, a system boiler has built in pump and expansion
vessel, whereas a regular boiler doesn't.
My current CH system has a pump in the airing cupboard, but I do not
think there is an expansion tank in the loft. Now I'm slightly confused
because I'm not sure if the current boiler has a built-in expansion
vessel.
So I'm looking for clarification on whether I need a regular or system
boiler.

Thanks.

On Jan 25, 11:17 am, wrote:
I need to replace my existing boiler with a new condensing boiler.
As I understand it, a system boiler has built in pump and expansion
vessel, whereas a regular boiler doesn't.
My current CH system has a pump in the airing cupboard, but I do not
think there is an expansion tank in the loft. Now I'm slightly confused
because I'm not sure if the current boiler has a built-in expansion
vessel.
So I'm looking for clarification on whether I need a regular or system
boiler.

Thanks.

Just another note to this - assume it's a regular condensing boiler I
need, then the one I'm looking at is the Worcester Greenstar 24Ri. This
is for a 4 bed house with 2 bathrooms, and 15 rads.

On 25 Jan 2007 03:17:36 -0800 wrote :
I need to replace my existing boiler with a new condensing boiler.
As I understand it, a system boiler has built in pump and expansion
vessel, whereas a regular boiler doesn't.

Correct (with exceptions)

My current CH system has a pump in the airing cupboard, but I do
not think there is an expansion tank in the loft. Now I'm slightly
confused because I'm not sure if the current boiler has a built-in
expansion vessel.

When the heating is on the water expands and the increased volume has
to go somewhere. You have an open vented system so the level the
header tank will go up a bit. The alternative - now generally
preferred, and required with many boilers - is a sealed system, where
the expansion is taken up by the expansion vessel: in simple terms
it's got a large balloon in it which compresses as the water expands.

Check out the sealed system FAQ at

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

--
Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk

On 25/01/2007 11:43 wrote:

Just another note to this - assume it's a regular condensing boiler I
need, then the one I'm looking at is the Worcester Greenstar 24Ri. This
is for a 4 bed house with 2 bathrooms, and 15 rads.

We had one of these installed just before Christmas. Four bedrooms, two
toilets, one shower room and 17 radiators. It copes extremely well and
has the house and DHW up to temperature in no time at all. We kept the
rest of the vented system with no alterations other than the location of
the pump: the hot water cylinder remains in the airing cupboard and the
expansion tank in the loft.

The only disappointment is the ugly black plastic flue protruding from
the wall. Pity Worcester Bosch couldn't have spent a few more pence on
something a little more pleasing to the eye.

--
Frank
(Beware of spam trap - remove the negative)