On Sat, 20 May 2006 19:02:49 +0100, Doctor Drivel wrote
(in article ews.net):


"Andy Hall" aka Matt wrote in message
...
..

- As soon as there is DHW demand, the boiler
cuts power to the second output, closing the CH
zone valve(s) and powers the first output, opening the
cylinder zone valve. It then fires up to full output
and flow temperature rising to 85 degrees output.

Matt, how does your boiler model know that DHW is calling if fitted with
either a stat or temp sensor?




There is a setting on the controller in the boiler to select whether the DHW
demand sensing is by a contact closure (i.e. thermostat) or a temperature
sensor.

There is a similar one for CH control where the sensing is between thermostat
contact, a PWM signal from a Siemens or other controller or 0-10 or 0-3v
analogue control.