On Mon, 22 Mar 2004 19:58:14 GMT, Lurch wrote:

On 22 Mar 2004 05:32:21 -0800, in uk.d-i-y
(stevep) strung together this:

I have a gravity fed HW and pumped CH system with a programable
thermostat. If I have the thermostat programmed to come on all day
inc. overnight then the boiler keeps tripping in to heat the water
despite heat not being required for the CH.
Can I fit a thermostat to the airing cupboard tank so that when the
room temp is OK the boiler will not light up or is there some other
easy solution?

There is nothing on the HW side of a gravity system that would bring
the boiler on, so it must be the room stat calling for heat.


In a simple gravity H/W and pumped C/H system:

a) The programmer will only allow the C/H to be on if the H/W is on.

b) The H/W terminal on the programmer powers the boiler.

c) The boiler uses its own internal thermostat to determine when to run.
(which it can only do when powered)

d) The C/H terminal on the programmer supplies power to the pump via a room
thermostat.

If you swop the room thermostat for a programmable room thermostat you end
up having to leave the boiler and H/W on all the time.

This can be avoided by either converting to Honeywell C or using a
Danfoss-Randall TP9.

Michael Chare