Nest thermostat with 2 hot water cylinders - how?

28 Nov 2021
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United Kingdom
Hello all, been a frequent visitor here for lots of tips over the years, but this is my first question.

I would like to upgrade my Drayton digistat 3 (central heating) and separate Drayton LP711 (hot water) controllers to a single Nest system that controls both CH+HW.
System is open vented.
Problem is I have 2 hot water cylinders, and I have been informed that the Nest can only control 1 cylinder.
Is this true?

All the S plan wiring diagrams I can find have one cylinder thermostat in the diagram so maybe it is true.
But surely the Nest would just replace the signal from the LP711 controller to demand the heating of the hot water cylinders, and the individual cylinder thermostats control the rest.
It's just the same as if the LP711 demands hot water heating but the tanks are already at 65deg then the 2 port valves won't open, or if one tank is cold then only that valve opens.
Anyone have any ideas on all this and if its possible?

Desire to install a Nest is that the digistat signal isn't great (don't want to move it closer), and we work pretty irregular patterns so changing the programming in the digistat is an absolute pain, plus had one in the old house and liked it.

Thank you all in advance
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Nest only provides a timed output for the hot water control. IE on/off, unlike the central heating where it also provides temperature control. So as you have figured there would be no issue with using the timed hot water control of Nest for two hot water cylinders and the thermostatic control would remain with the two individual cylinder thermostats and their associated motorised valves. The only restriction is that the hot water 'on' times for both cylinders would have to be the same. However, as you are presently using one LP711 for both, I assume that is not a problem for you. If so, crack on (y)

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