"Set Square" wrote in message
...
In an earlier contribution to this discussion,
Pete wrote:

Are you *sure* it is a gravity system?

99.9% sure. HW circuit is not pumped, only central heating - see below.


How does looking in the loft prove that it's a gravity system? I wonder
whether we mean the same thing by "gravity system".

I am talking about gravity (or natural convection) circulation within the
*primary* hot water circuit. If this is what you have, you will probably
have *four* water pipes connected to your boiler - 2 large (28mm) ones
which
go to the indirect coil in the hot water cylinder, and two smaller ones
(22mm) for the central heating - with the pump being somewhere in that
smaller circuit - and with the primary flow in the HW circuit being
*unpumped*. Is that what you've got?

Not quite. I have TWO 28mm pipes going to the boiler. These 28mm pipes form
the HW flow and return.

From the 28mm flow there is a T piece and a 22mm pipe connecting to the pump
and then continuing to the CH flow.

CH return connects from a 22mm pipe to the 28mm Return via a T.

Is this still what you mean by gravity. - Would a diagram help?