Heating controls for vaillant ecotec boiler and UFH

[davphi338]

Hi,

I want to install a single zone underfloor heating pack similar to this
http://www.screwfix.com/prods/48974...ng/JG-Speedfit-Underfloor-Heating-Pack-of-30m

I currently have a vaillant 360RF wireless programmable room thermostat to control my rads on the combi. I beleive this setup will not be suitable for use to control a UFH setup with an additional thermostat.

What would be the best way to connect this pack to my existing heating system and how would I control it. I've trawled the internet but cannot find detailed information. If I have to scrap the 360RF and use a different programmer so be it and I don't mind if the UFH only comes on when the boiler is operated for the radiators if this makes things simpler.

 

[spudkey]

Do away with vailliant controls use honeywell and connect ufh as extra zone wire back from new wiring center to terminal 4 on boiler

 

[simond]

We installed one of these Speedfit kits last year.

I believe you can use it standalone, so it will only come on with the rest of the heating. The mixer valve etc will still work.

I would try it this way before throwing the ebus controls out.

 

[Tipper]

I always assumed that the VRT 360f, when in 'analogue' mode, was originally intended for UFH due to its modulation of the circulating water temperature, which is more suited to UFH, rather than the more traditional 'two-point (on-off)' heating of radiators.

I would try it first using analogue, see p39 of the little instruction book, before scrapping the controls and stating again. Analogue control ensures the boiler stays in condensing mode for much of its operation which should be more economical.....or so they say!

 

[spudkey]

The ufh should be it's own zone as it will require different time settings to rad circuit Vaillant controls do not allow for more than 1 heating zone
As I said convert to S plan with additional zone for ufh

 

[davphi338]

Thanks for all the replies. It gets more complicated the more I read. I thought these single zone kits for extensions and conservortories were meant to make things simple.

Can someone clarify a few things for me:

I currently have a vaillant ecotec combi with rads. To install UFH in a new extension will I have to run new pipework all the way back to boiler to be able to have UFH. I can get access to the 22mm flow/return pipework in my old airing cupboad but I think the rads in my bedroom will have already been tapped off before this point.

Looking at the installation diagrams for kit such as this:
http://www.floorheatingonline.com/shop/pdf/room-pack-manual.pdf

The scematic suggests the manifold and 2 port valve is fitted on the flow and return but the rads are tapped off before the 2 port valve. From my limited knowledge it would seem to me that the system would operate as such:

1. UFH thermostat will call for heat and activate the combi boiler and UFH pump. Am I correct in thinking that in this setup the normal rads will also heat because they are before the 2 port valve.

2. The room stat for the rads activates the boiler but if the UFH heating stat is not activated only the rads will heat.

If this is the case whats the point of the UFH stat and 2 port valve as you might as well operate whole system from the normal room stat.

I may have got myself completley confused with these single zone packs
but as I only require the heating to warm the tiles I may now opt for something called a floor rad that is simply pipework in the floor controlled by a danfoss valve.

Any advice would be much appreciated.

Edit:: Looking at it more closley would I be correct in thinking that for the system to operate correctly I would have to purchase another 2 port valve that would be used to control the flow to rads ??

 

[spudkey]

You basicaly have to split the heating flow pipework between the boiler and first rad at this point you fit tee to ufh and a zone valve on rad circut
All wiring will go back to a wiring center from this box a cable will go back to terminal 4 on boiler
With this setup if either the room stat on rad circut or ufh stat call for heat it will fire the boiler but they will work independantly
This will slow ufh to run at different times to rads
Ufh needs to run for longer periods at lower temps as it has slow response time it should not be turned on and off like rads

 

[davphi338]

Thanks spudkey. I've been stood in my extension and old kitchen wondering how I would be able to get new pipework and cable back to the boiler and then it all became obvious. I can run the pipework along the edge of the wall just below the ceiling and then box it in. This will also give me the facility to run new cabling in for new stats and valves.

Anyone want to buy a vaillant 360RF wireless programmable room stat. Not much use to me now.

 

[davphi338]

One last question, for now anyhow. Would it be OK to run the flow/return to the UFH in 15mm. The pack is for coverage of 24m2 and the distance to the boiler will be a run of approx 8m.

 

[davphi338]

Knew it wouldn't be long before I was back.

Spudkey, could you give me a little more info on the wiring arrangement.
All the wiring at the manifold seems reasonably straightforward as it is all detailed. What I would like to know is the switched live from the UFH pack will go to the boiler wiring junction box and I'm presumming that the only other wiring in this control box will be the wiring for the 2 port valve for the rad cct, the wiring for the room stat for the rad cct and then a wire for terminal 4 on the boiler. I've tried looking at 'S' plan schematics but I don't think think they are normally relate to combis where the pump is all internal.

From my understanding the switched lives from each of the room stats will be commoned and they will connect to terminal 4 of the Vaillant boiler. It is then a matter of working out how to wire the 2 port valve for the rad cct with rad cct timer and I think I'm nearly there.

thanks for any advice

 

[davphi338]

Think I've sorted it in my head now. What they call switched live from the UFH pack will actaully be the CH call from the 2 port valve (orange cable). The programmer for the Rad cct will be wired in to activate the 2 port valve for the rads which will then supply a CH call orange wire also. It is these 2 orange wires that will be commoned and connected to terminal 4 in the boiler. I take it there are no other connections required to the boiler since its a combi.

If I've made any obvious mistakes in my thoughts please let me know.

All I need now is to source a replacement RF programmable room stat to replace my Vaillant one.

 

[spudkey]

hj

 

[simond]

The Speedfit unit will work on the existing rad tails.

The UFH will come on whenever the rads are on, when the Speedfit prog room stat is calling for heat.

Converting it to zone valves is the better option but requires lots of pipework and wiring. As you are now finding out.