On Wed, 3 Nov 2004 20:56:25 -0000, "IMM" wrote:


"Ed Sirett" wrote in message
news
On Wed, 03 Nov 2004 10:42:10 +0000, IMM wrote:


Some of the control systems that are now being used in some boilers are a
significant (even you might say a quantum) leap ahead than simple on/offs.
Some of them are sophisticated enough to work out a good enough strategy
simply from the on/off signal and the return flow return temperatures.

They do and that is designed for the heating function. DHW usually throws
them, unless they know it is DHW by a signal from a stat.


Which is not that hard since something will be switching motorised
valve(s) anyway.

I have mine set up to work the opposite way around to conventional
Honeywell plans

The boiler is given outside temperature, cylinder temperature and room
controller data as inputs. There are a choice of functional
programs for different valve or external pump configurations using
three relay driven outputs.
I use one where the boiler has control of opening heating motorised
valve(s) or DHW valve as required - in effect an S plan configuration
but with the boiler acting as controller and no auxilliary contacts
used.

When a hot water cycle is needed as monitored by the cylinder sensor,
then CH valve is closed and HW opened together with full power.
On completion, the CH operation is recommenced by closing the HW valve
and reopening the CH.



--

..andy

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