On Mon, 20 Dec 2004 22:25:32 -0000, "Set Square"
wrote:

It sounds from what you say that the radiators only get hot when there is
*also* a demand for domestic hot water. Has it ever worked properly? If not,
it has not been installed and/or wired correctly. From your photos, you have
a Y-Plan system - fully pumped, with a mid-position 3-port valve to direct
the water to the cylinder and/or radiators. [See
http://content.honeywell.com/uk/homes/systems.htm and scroll down to Y-Plan]

This system requires the programmer to have a "HW Off" terminal in addition
to "HW On" and "CH On" and it also requires the cylinder stat to have
change-over contacts. If this is not done, the system won't work in CH-only
mode.

When I moved in here I found a superb CH system, with the most amazingly
crap wiring system imaginable.

The house was divided into three zones, so there are four 2-port valves.
There is a hot water/CH timer. There are no thermostats anywhere in
the house, not even on the tank.

When the hot water part of the timer is on, it fires up the pump and the
hot water valve. When the CH part is on it goes through three switches
on a very nice, custom made and labelled, switch panel to the three zone
valves. The boiler is on all the time.

To keep things "tidy", the installer had carefully removed the
multi-core cable from the valves and replaced it with 3 core, not using
the microswitches at all.

I'm still speechless thinking about it.

We now have three room thermostats, each turning on the appropriate 3
port valve, as does the new tank stat. The four microswitches in the
valves have been reinstated to activate the boiler. The pump overrun
output from the boiler, which was previously u/c now runs the pump.
--
On-line canal route planner: http://www.canalplan.org.uk

(Waterways World site of the month, April 2001)