S-plan with single channel timer

[cyrix2000]

Hi,
I moved in a new home and trying to understand the set-up of my central heating system.

I have a heat only boiler (Ideal Logic Heat), two heating zones (with Danfoss room thermostats and one motorised valve each) and a closed hot water system (with it's own valve). The timer is a Danfoss single channel timer. The system is wired up as s-plan.

Now my question: what is controlling the hot water demand? As far as I understand the system has hot water priority, so the two heating valves close and the hot water valves opens, if the tank thermostat is flagging heat demand for the hot water tank. But what is controlling this? The boiler or is there somewhere a separate controller for that behavior?

In all s-plan diagrams I found so far, the timer has always two channels, one for heating and one for hot water. How does it work with a single channel timer?

Thanks for your help

 

[Whitespirit66]

Yours sounds like it's loosely based on the S-Plan. Normally, there would be a 2 channel programmer, but as yours has 2 zone heating valves, 3 channel is another option (hw + ch zone1 + ch zone2).

The hot water demand would be controlled firstly by the programmer. If this is on for hw (inc ch in your case), the cylinder stat is the next control. Is there a stat on your hw cylinder?

Hw priority isn't the norm with S-Plan. It's usually hw, ch or both. It's possible that someone has configured your system for priority hw. Do the ch motorised valves actually close when there is demand for hw - usually from cyl stat? Another possibility is that your system is badly balanced, and when hw is calling, the hw cyl robs heat from the rads and they cool until hw goes off again.

Without seeing the system and how it's wired, it's difficult to be exact over t'internet.

 

[cyrix2000]

Yours sounds like it's loosely based on the S-Plan. Normally, there would be a 2 channel programmer, but as yours has 2 zone heating valves, 3 channel is another option (hw + ch zone1 + ch zone2).

It seems to work with a one channel timer/programmer and two room stats.

The hot water demand would be controlled firstly by the programmer. If this is on for hw (inc ch in your case), the cylinder stat is the next control. Is there a stat on your hw cylinder?

Yes there is a stat on the cylinder which seems to control the inlet valve the hw circuit.

Do the ch motorised valves actually close when there is demand for hw - usually from cyl stat?

yes, both ch valves are closing if there is demand by the cylinder stat

Here a few images of the system set-up:
View media item 72234 View media item 72236 View media item 72237 View media item 72240 View media item 72241 View media item 72242
The reason for all of these questions is that I want to fit a Tado controller (www.tado.com) and I'm trying to figure out how to best integrate it in my setup...