On 12/01/2019 14:40, Harry Bloomfield wrote:
John Rumm formulated on Saturday :
I suspect they are talking nonsense or at crossed purposes. It may be
that it can't be done with the installation you have, however if you
are prepared to add controls then it looks straight forward.

All I have at the moment, is a Danfoss (I think) time clock, which sets
when CH and HW are available. A three port valve. A wireless room stat
and a wired HW cylinder stat.

The original boiler had just a live (when called) neutral and earth. I
added an extra pair in from boiler back to pump, to enable to boiler to
decide when the pump needed to be run, when the new boiler was installed.

So you would need a bit of rejigging to move to split temperature
operation. The VR weather comp replaces the timer and stat. You probably
want a pair of two port valves in place of the mid position valve -
although with a bit of thought you may be able to achieve the logic
required with what you have. Swap the cylinder stat for a NTC
thermistor, and add a suitable wiring centre. You would need an extra
cable from the cylinder to the boiler (that threw me, I was expecting
the cylinder NTC to connect to the wiring centre!), and to install an
external NTC somewhere.

Doable enough, but whether its worth the hassle at this stage only you
can decide. It might knock a few percent off the gas bill, and will make
the place a bit more comfortable year round.


--
Cheers,

John.

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