JG Underfloor Heating System Wiring

[Dean Mansell]

Hi,

After being let down by numerous builders / plumbers over the last 12 months I've decided to take on our lounge refurb project. Managed to get the various trades in to get the room ready to install the John Guest UFH system I've purchased. Not had UFH before but fancied giving it a try in the newly insulated (floor and walls) lounge and if goes well, adding to a further 2 rooms. The system looks easy enough to install so giving it a bash myself, however may get a plumber to plumb in the manifold.

The question I'm hoping somebody can answer is regarding the wiring. I have an Alpha CD35C combi boiler running the central heating (radiators) and recently replaced the old wireless thermostat with a Nest. The Nest works great so I've purchased another to control the temp in the lounge that will have UFH. Here's where I get a bit confused. I didn't get the 8-zone wiring centre and thermostat controls from JG as I'm using the Nest. Looking at the JG install manual I'm now wondering if I do actually need the wiring centre?

The other question is how do I wire the boiler so that the UFH system calls for hot water without the central heating and rads coming on? Any help much appreciated. It may well be I have to give in a get a professional in...but where's the fun in that!

 

[Madrab]

If you want individual UFH loop and other zone control then yes a wiring centre and actuators on the manifold are recommended.

You could set up Nests to control each zone but you are then getting into manual wiring and controlling each actuator with each Nest controller etc with a switched live to the boiler for each call but it could get very complicated, very quickly doing it that way, number of zones dependent.

 

[Dean Mansell]

Many thanks for the reply. I've got a 6 port manifold with the idea of expanding to 2 further rooms in the future if we like UFH in the lounge. I was advised by JG that my lounger requires a single loop, the 2 further rooms require 3 and 2 loops giving a total of 6. My plan is to initially install the single loop lounge and have it as it's own zone, working separately to the radiators. How does the UFH call hot water from the boiler without the boiler feeding the radiators? Do I need some sort of extra valve on the UFH? I have 1 x actuator valve supplied in the kit along with the UFH 14KW control unit (Inc mixing valve, pump & fixings).

I've been on to JG's tech support webchat this morning and the guy on there said for just the one zone (port) I do not need the wiring centre and can wire direct. If and when I want to use the extra loops in the other rooms I would then need the wiring centre.

 

[Madrab]

How does the UFH call hot water from the boiler without the boiler feeding the radiators

At the moment, can I presume you have 1 thermostat that control everything, therefore when that stat calls for heat, both the central and the underfloor heating all come on?
You may have the UFH controlled by it's own stat, that then controls a 2 port valve and the valve then energises the switched live to the pump and boiler through a normal s/y plan wiring centre.

The easiest way to control each loop or zone if there are more than a couple is to use a stat for each zone and a specific UFH wiring centre that has a radiator loop out to power the boiler/pump/2 port valve.

 

[Dean Mansell]

Kind of. I currently have a nest thermostat that controls the the boiler that currently only feeds the radiators. I'm wanting to add the UFH and control that from a second nest thermostat. I may well of added confusion with having the larger UFH manifold for future expansion. For now (and probably forever) the manifold will only supply the one loop into the lounge. I think your explanation of 2 port valve has answered my question, I didn't understand how the UFH and radiators can be fed independently from the boiler with one not affecting the other

 

[Mr Chibs]

I have two, 2 port zone valves and two thermostats, one does the house... the other one does the UFH... mine is in one room.

It works well, as they can be on separately. Think my boiler (combi) is set to S Plan.

 

[Dean Mansell]

Great to hear from somebody who has the same system and it works - I have a way forward! Really appreciate the replies and info, I'll keep you posted how it goes