I may be having my regular open vented boiler soon replaced (see my
earlier thread). I have several thermostatic valves, which I bought
some 10 years ago with the intention of fitting them, when we last had
a new boiler installed and the system drained and flushed, but the
boiler was replaced when I was working far from home - so it never got
done.

I am thinking this time I will be home and could install them, but with
no working boiler there is no easy way to work out which is the flow,
which is the return at the rads. How can I work out which is which,
without a working boiler and without lifting lots of floors?

I cannot remember how many such valves I bought, but assuming I have
less than enough for the entire building, where are the best places? It
is a semi- detached. I will find and count them up later.

1. Hall, which is where the stat is, so a valve should not be fitted.
2. Living room, close to the above.
3. Kitchen
4. Downstairs toilet, close to back door of an unheated foyer, so
always cool unless the door is left closed.
5. Utility room, again off the above foyer and never really gets to
comfort warmth due to poor insulation and a cool foyer.
6. Bathroom/ toilet upstairs.
7. Back bedroom
8. Front main bedroom
9. Small bedroom, used as a small work area/ office.

The living room gets too warm maybe on an evening, if the door to the
Hall is closed, too cool when it is left open.

Sometimes the front bedroom can be too cool on going to bed, sometimes
it is fine. It seems to depend on the weather/ when the boiler last
fired.

Likewise the bathroom.

I am thinking thermostatic valves will help divert the heated flow
better, to where heat might be needed. None of my radiators are
presently balanced, they are just all wide open.