On Wed, 24 Nov 2004 23:22:27 +0000, Hugo Nebula abuse@localhost
wrote:

On Wed, 24 Nov 2004 22:30:02 +0000, a particular chimpanzee named Andy
Hall randomly hit the keyboard and produced:

THe normal arrangement is then for a signal wire from the motorised
valve to go to the boiler switched live. This wire is live if either
thermostat demands and the motorised valve is open accordingly, and
fires up the boiler. Once this live goes away because the
thermostats are satisfied, the boiler is shut off apart from being
able to run the pump to disperse heat.

I think from the behaviour of the boiler when the programmer goes off
there isn't a pump overrun.

You mean it tends to sing and make bumping noises? If there is a
pump over-run it may not operate for three reasons

- Boiler thermostat is buggered but pump is still powered via
motorised valve or controller.

- Over-run not connected

- Over-run not needed because water cools quickly or is cool enough
when burner goes off.


You could incorporate a flow switch, but normally the other controls
do the job.

If there wasn't a room thermostat, what would happen then?

If you are just relying on the boiler thermostat to control the room
temperature then there is noting apart from the timer to turn off the
heating. This isn't much different from the over-run point of view to
a room thermostat turning off the boiler when the room is warm.
Either way the burner can be turned off when at full power and the
system is hot. Possibly though, if you are using the boiler
thermostat to control room temperature, the boiler water temperature
will be some way below the intended 80 degrees.



--

..andy

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