Re: [OT] well, sort of. Central heating radiator plumbing

[James Hoye <y@xxxxxxxxxxxxx>]

ian.bird@xxxxxxx wrote:
> Hi all
>
> I cannot find after a while Googling how central heating radiators are
> typically plumbed in. I have a conventional heating system i.e. fully
> pumped but not pressurised and I want to know how the radiators are
> plumbed back to the pump.
>
> I am trying to control my heating with much better accuracy,
flexibility
> and complexity (it is HA after all). To this end I need to know what
will
> happen if I turn off radiators seemingly randomly around the house
> depending on individual room conditions. I am assuming at this point
that
> none of the radiators are plumbed from one into another otherwise when
one
> turns off then the water won't get to the next!!
>
> Does a typical system have a manifold with individual feeds to each
> radiator so turning one or more off won't have a dramatic affect on
> others?

Usually for this type of system you have a 22mm feed and a 22mm return.
Radiators are usually plumbed in 15mm across the two:

F==================================

X        X           X        X
X        X           X        X
X        X     B      X        X
X        X           X        X

R==================================


F=feed
R=return
= 22mm
15mm
XXXX radiator
B = optional bypass valve

Closing off the valves on any radiator should not affect any other.  One
word of warning though - when TRVs are fitted, there is usually one
radiator (bathroom for instance) that has normal lockshield valves on -
this is so that if all the TRVs close down, the pump can still circulate
the water and the radiator will allow the heat to be dissipated.
Sometimes a bypass valve is fitted (usually in airing cupboard) across
the loop and works on pressure differential to prevent "system
meltdown"
if all of the valves are closed.

James