In article , Mike Barnard
writes

I have now decided to zone; 2 zones, 1 upstairs and one down. Many
thanks to the posters who have given advice. The house is too small
and tight to put more pipework in than this. Now my remaining
questions are...

1. Can I use a common return? (There was an answer in the previous
thread but it made no sense to me.) If zone 1 is operating and zone 2
isn't, can there be a problem with using common returns?

If you see an answer that you don't understand then the original thread is
the place to query it rather than starting a new thread.

2. Can you reccomend a RELIABLE valve to use for just two zones?

Honeywell 2 port valves (22mm) as they can be obtained at reasonable
cost from discount outlets and replacement parts are readily available in
the event of failure. They can still fail so don't bury them behind nailed
down floorboards.

3. What about 'primary' rooms and rads without TRV's? As I understand
it, the rad in the primary room (the room with the controls in, yes?
Thats the open plan lounge in my house) should have no TRV. Do I need
a primary room in each zone?
Yes

What if the controls are in the upstairs
hall which has no rad?

Controlling upstairs rads from a stat in the hall where there is no rad and
where heat flow could be restricted by closed doors would be a mistake, if
you chose not to split the upstairs then you need the stat to be placed on
the cold side (bed)room and the TRV on the warm side (bed)room.

The general rule is that that the (global) control should be in the slowest
room (area) to heat up and the fastest room (area) to cool down, in that
way the secondary areas should be neither too hot nor too cold.

Don't worry if you have difficulty understanding these concepts as few CH
technicians will have a better grasp.
--
fred
Plusnet - I hope you like vanilla