On 15/01/2016 14:16, Bob Minchin wrote:
Harry Bloomfield wrote:


With your electronic skills, you should be able to modify the boiler
for dual temp setting.

The sensor is usually a thermistor. I bought one as a spare part on
ebay for a few quid and measured it at various temperatures and found
that it closely complied with one of the standard curves for
thermistor sensors.

With a relay you can switch in an extra resistor (or variable
resistor) in series or parallel the flow temp sensor and drive the
relay coil from the DHW demand signal to give one setting for CH and
a boost for DHW.


or use an IN4148 diode :-)