On Sun, 9 Nov 2008 21:05:29 -0000, "Roger Mills"
wrote:

In an earlier contribution to this discussion,
wrote:

I have replaced Ch rads etc etc on my old system but now I have a
sealed system ( Combi) and I want to sometime in the future move or
replace a rad or two. I know it's not the ideal time of year to be
doing this but I need to do it when the urge takes me .
I want to confirm what I need to do so here's what I intend doing and
would appreciate if you could point out anything I have missed or
don't need to do .

(1) switch off power to boiler.

Yes.

(2) switch off water supply feeding boiler ( is this necessary ?)

Not necessary.

(3) Drain down system ( there is a drain tap under the floor beside
boiler),opening bleed valves to assist this

You don't need to drain the whole system. Turn off *both* valves[1] [2] on
any radiators you are not touching, to keep then full during the operation.
You'll then only need to drain the pipework - and won't need so much new
inhibitor (assuming you have some already!)

(4) move and/or replace rads .

Yes

(5) Close bleed valves ,Close drain tap,feed system with Sentinel
using the installed filling point ,open water valve and open filling
loop to around 2 Bar

There are various ways of adding inhibitor. I made a device to pour it into
the top of an empty radiator after the blank plug had been removed.

(6) Open bleed valves to expel air while watching water pressure and
open filling loop if required . Continue doing this until all air is
expelled .

You may need to top up via the filling loop several times.

(7) switch power on and fire up boiler ,checking for any further
necessary bleeding .

That's about it!

[1] Make a note of how many turns it requires to close each lockshield valve
so that you can restore them to the same position.

[2] If TRVs are fitted, remove the heads and screw on the supplied
decorating caps to make sure that the valves stay closed however cold it
gets.

Thx for that .I pretty much got it right . I think I've got
decorators caps for the TRV's..they are all fairly new .