Is my UFH installed in a standard way?

[Steve Harper]

Hi all,

I have what I think is called an "S Plan+" central heating system. That is there are separate zone valves for DHW and each heating "circuit". It was fitted around 14 years ago when my house was renovated. There is UFH in kitchen, rads elsewhere; it's a 3 storey large house.

The manifold, pump etc for the UFH are situated about 6m away from my boiler, both of which are in the basement of my house. The UFH is for a large kitchen/breakfast room approx 10m x 6m plus a utility room.

The on/off times for the UFH as well as DHW and rads circuit are controlled by a Horstmann 3 channel programmer sited next to the boiler. This sets the on-off times for each circuit switching on the boiler and the DHW and rad zone valves. As far as I can tell the (wired) thermostat for the UFH only controls the UFH zone valve - that is to say there is no wire from the UFH 'wiring centre' to the boiler.

Since the kitchen floor (the one with UFH) is stone tiled, I was advised on installation to keep the UFH 'channel' of the programmer on permanently (due to the thermal latency in the stone floor I guess).

ISTM that with my boiler on 24/7 I am permantly heating the 6m flow & return pipe from boiler to UFH manifold & pump (in my cold basement) even when the UFH is up to temperature. Yes, I know the zone valve will be closed in these circs but none the less it doesnt seem very efficient to me - am I missing something here???

Likewise I have no room stats but TRVs on all radiators. With the Horstmann 3-channel controller only operating zone valve and switching the boiler on or off according to the times set, my boiler is running whenever any of these channels are 'on' is it not? Obviously the boiler cuts out when it is 'up to temperature' but thats only a boiler decision, its not affected by UFH or radiator / room temperature. The boiler is a Keston C40 btw.

Just wondering if this sort of arrangement is normal?


Thanks for any advice - I am looking to replace all heating controls in my house with something 'smart' but I'd like to understand a little more about what I actually have right now.

 

[Madrab]

Any CH pipes that are within an unheated space should be well insulated.

If the UFH channel on the programmer is set to always on then the room temperature should be controlled by the room stat, that room stat should then control the 2 port valve and then the valve should control the boiler switching.

Look up S plan plus wiring.

 

[picasso]

No it sounds like a bodge, the ufh stats should control the zone valve as should the room stats that you dont have, it shouldn't be difficult to install rf stats to your existing system.

 

[cross thread]

It’s not the best way to control if for efficiency, as mentioned wireless thermostats could be added to save disruption to the property

 

[Steve Harper]

Thanks for the help guys.

From Madrab's reply it seems like I should look a little closer to see if there is a connection to the boiler from the UFH zone valve (which is on a wired thermostat).

From picasso & cross threads posts I guess I should look at RF room stat(s) wired into the zone valves for the rad circuit....

I'll take a closer look at my wiring and an s plan plus wiring diagram.

Thanks again

Steve

 

[Madrab]

Look to see where the orange wire from the the 2port valve is going.

 

[ianmcd]

I should look a little closer to see if there is a connection to the boiler from the UFH zone valve

The zone valve wont connect directly to the boiler, wou will have a wiring centre and all 3 zone valve orange wires will connect to the same terminal and the boiler switched live will also be connected to this terminal

 

[Steve Harper]

Okay, thanks!

Steve