Underfloor Heating Cabling

[Nick Barton-Wells]

Hi all

I am just finishing the cable runs back to the cab and have got myself into a question i am struggling to answer.

Currently, we have underfloor heating upstairs and downstairs.  This means we have 2 manifolds on both levels of the house.  "Currently" i have run 3 cores to each pump and valve.

I am now considering if i should have run the 5core cable.  My plan was to let Loxone coordinate boiler demand, valves, and pumps directly.  I Don’t want to bother with the end switches, because they’re redundant once you’ve got smart logic.

[Jonathan Dixon]

If designing from scratch I'd run 5 core there "just in case" but in reality, so if it's easy for you to do it now then why not, but as you have Tree at each manifold anyway you'll be totally fine with twin and earth cable even.

Wire each pump from the microswitch output of the manifold valve, and drive that from the relay switched output. This will run the pump after the valve has fully opened, and shut it off when the valve begins to close. OR if necessary connect the T+E permanently powered and add Tree Nano Relay(s) to locally switch pumps/valves etc as needed.

If by 3 core you mean 3+E then you could remotely switch the valve and pump independently per your schedule, but TBH there's not a lot of benefit.  I assume you have a thermostatic mixer there, so if that is fully open you'd not want the pump running with the 2-port zone valve closed anyway - and the switch output from the valve mentioned above achieves this for you. [If you're doing electronic mixing valve you need a lot more stuff: 2 more switched cores plus pipe temp sensors - and unfortunately there's not sane way of doing temperature sensors over Tree ]

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[Nick Barton-Wells]

Joth.  Thank you very much for the reply.   Really appreciate the time taken to explain the answer
To be honest, i hadnt thought of using the switch live from the valve to power the pump.  Meaning just a single 2core +E cable is sufficient.

Having 2 core +E cables run to to both valves and pumps means i now have the choice.
Do i wire them all independently using 4 relays or do i use a single 2 core +E cable and using the switched live from the valve to turn the pump.  This means 2 relays needed

Thanks

[Paul Watkin]

Nick, Just adding to Jonathan's comments I would also suggest talking to your plumber about the 2 port valves and using the end switch to control the pump, in my experience most heating engineers don't like omitting the end switches as if the valve fails to open for some reason you will be pumping against a closed valve and likely to damage pumps and or boiler if it doesn't get proper flow once fired.

I had a lot of trouble initially getting plumbers to understand Loxone in terms of heating - the easiest way i found to explain it was telling them that Loxone was essentially a fancy room stat that called for heat from a Relay channel just like any other heating controller would.

For our newbuild I have run the following to each of our 4 Manifolds, a 5core cable per 4 manifold actuators (common neutral), a Tree Cable, 2 Core T&E for the pump, a 5 Core for a future blending valve and a Cat 5 for the 1 Wire sensors installed in the manifolds.

I have yet to decide on whether to use Tree actuators or standard Mains ones hence the addition of the 5cores for actuators

A further 2x5 core will run from the heating wiring center to the Call for heat relays (Miniserver) to open the 5 2-port valves (4 heating plus DHW) - the 2nd 5 core also takes the perm live power back to the relays from the wiring centre to make sure that isolating the power to the heating wiring centre isolates everything rather than have the potential for call for heat to come live whilst someone is working on it.

Adding SFCU's local to the pumps to allow for proper safe maintenance of the pumps is also essential

[Nick Barton-Wells]

Amazing Paul..  Thanks for the reply.  Some fantastic information.
I have SFCU's at every pump and valve since i was going to operate them independently but now having moved to using the switched live from the valvle, i have a spare switchable live from Loxone.

I have really struggled to get the plumber and electrician onboard with Loxone.  The plumber has been better since i explained that Loxone is essentially a bunch of on/off relays. 

I m planning on using Tree actuators so have tree cable at both manifolds.

Thanks

Nick