UFH wiring

[studentspark]

I have a wet UFH to wire up.
Its all been plumbed in, and the plumbers have long gone, so I can't ask them these questions, so I hope some one here could advise.

The existing heating system is an s plan
A single zone wet underfloor heating zone needs to be added, so an S plan Plus.

The heating and hot water are controlled via a nest stat.

The UFH could be switched on with the heating, but Im thinking its better to have it on its own stat, so can come on earlier, and be set to the room.

The pipe work up to the UFH manifold is hot, as its fed from the heating (radiator) circuit. and is stopped from flowing into the UFH circuit by the two port valve on the manifold.

This is where I start to get a bit unsure.

The manifold has no instructions, and no makers mark for me to look it up.
Its only a single zone, but, it looks like they could be two, and it has it has no actuator heads.

So I am wondering if the flow to the UFH is controlled by the manifold two port valve, as there is no wiring centre with the manifold, and no actuator heads to power on or off.
So when the two port valve opens, via the new UFH stat, it switches on the manifold pump, (and the boiler pump and the boiler, if not already calling) and hot water flows to the UFH.

Does that make any sense at all

many thanks

 

[ericmark]

There are two ways to control wet central heating, on/off and analogue. Nest can do either, with oil boilers likely simple off/on, with gas boilers it may be more complex. So is OT1 and OT2 in the Nest thermostat used? If not simple on/off if it is then analogue.

Bit beyond my ken as well, if analogue then think pump speed is changed.

 

[stem]

Those I have seen were wired so that the UFH zone room thermostat switched on the manifold pump and also opened the motorised zone valve, then the microswitch inside the zone valve controlled the boiler and main pump in the usual way.

 

[SimonH2]

That is indeed a 2 loop manifold, with one unused. The white-capped valves on the bottom are used to turn each loop on/off (and in most installation would have thermo-hydraulic actuators fitted for individual zone control); and in the top are flow indicators so you can see how much is flowing around each loop, and I believe these also include adjustable restrictors to balance the system..
Below the pump is the thermostatic mixing valve (TMV) which sets the temperature flowing round the loops - most of the flow is just circulated round the loops, with sufficient fresh hot supply mixed in to maintain the set temperature.

As already suggested, connect the pump and zone valve (brown & blue) to the controlling stat/controller/whatever and connect the grey wires across the boiler demand circuit - ie treat the zone valve as just another zone valve in S-plan +. The only issue here is that the pump will be deadheaded for a short time between switch on and the zone valve opening. This shouldn't be a problem as the duration will be quite short - and it will only be a full dead-head if the system is cold enough for the TMV to be calling for 100% hot from the boiler and 0% recirculated.

EDIT: PS, that's a "somewhat overspecified" manifold setup for a single loop ! It's possible to buy setups made specifically for a single loop that omit most of the valves and gauges - and they are physically a lot smaller.