Underfloor heating with system boiler design

4 Jun 2016
Reaction score
United Kingdom
Hi to all plumbers out there. Looking to confirm my understanding of my underfloor heating design as I'm getting conflicting info from my plumber, my electrician, and my underfloor heating tech support :(

I have a system boiler with an unvented cylinder "behind" a 2 port valve, a 4 zone underfloor heating system in the ground floor behind its own 2 port valve, and another 4 zone UFH system in the first floor again behind its own 2 port valve. My understanding is that a programmer of a sorts will control the overall system by turning on and off the valves depending on a clock I set for what times I want heating and hot water on as well as input from the cylinder thermostat, is this correct?

Then the two UFH systems have their own thermostats for each zone so they control what they do with the hot water they receive accordingly.

So in terms of connections:

- all the two port valves have to connect to the main programmer

- main programmer connects to the boiler as well

- UFH wiring centres seem to require connections to the boiler "enable" as well but this is the bit I'm struggling to fit with the rest.

Can someone explain to me how everything fits together in simple terms please and what I'm missing from the above?

Thanks in advance!
Sponsored Links
Each zone regardless of the emitter type should have it's own programmable room thermostat.

Timer only needed for the hot water.

A 2 port valve on the ufh is not needed or recommended.

Wiring centres should then be self evident.
Thank you Dan for the response. So the timer only controls hot water so it only connects to the boiler and the cylinder 2 port valve, correct?

And then yes you're right, all zones in both UFH systems have their own thermostats. Does this mean then that the wiring centre for each UFH connects to the boiler and the relevant 2 port valve? For better or for worse I have the 2 port valves in place now so yes it's one extra component that could fail...

Thanks again
Connect the "boiler enable" from the ufh wiring centre to the brown of the 2 port valve, valve opens and the orange fires boiler, repeat for other ufh zone.
Sponsored Links
You can keep the zone valves as Picasso says and use them as a "relay" to start the boiler.

Or they could be disconnected and locked open manually and each zone controller used to start the boiler.

That assumes each zone controller is suitable to provide the boiler start signal ( without opening all the other zones! )

Thanks guys, it's clearing up in my head slowly. So:

- each UFH wiring centre (besides obviously connecting to the UFH zone thermostats) has to only connect to the boiler (either through the relevant 2 port valve or directly as Tony suggested)

- hot water timer / programmer connects to the cylinder thermostat which is connected to the cylinder 2 port valve which is ultimately connected to the boiler

Does the above capture it fully?
Maybe, but it is always difficult to work out what other people are thinking.

We don't know what kind of wiring centre controllers you have and what they are capable of and how they can be wired.

I don't know if you can understand why I added "without opening all the other zones!" and if not you might have a problem.

I appreciate it's difficult yes. Since the 2 port valves will be controlled individually and in isolation by the relevant system then I don't see any concerns with opening up the other zones. Of course it's entirely possible I'm missing something but I wanted to grasp the whole high level connection concepts and my electrician and plumber should be able to work it out now.

Many thanks.

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

Sponsored Links