Changing 230V switching to 24V

[MNW67]

I have a Drayton LP811 timeswitch which at the moment is used as one of the controllers on a standard S-Plan+, switching at mains voltage.

Could I change this to switch a 24V feed instead? The manual says it has "volt free contacts". Is it simply a matter of removing the link between L and COM and connecting a 24V feed to COM instead?

 

[RandomGrinch]

The (extra) low voltage wiring can be connected to the 'volt free' contacts, on terminals 1 and 3, if the link between L and 1 is removed.

Usually you wouldn't be connecting a 24V feed. You would be connecting a new cable/flex to the ELV terminals on your boiler.
However, there are a lot of mains operated controls on an S Plan+ system, so I don't know how you intend to mix the voltages. Is this related to the posts about X Plan systems?

 

[MNW67]

The (extra) low voltage wiring can be connected to the 'volt free' contacts, on terminals 1 and 3, if the link between L and 1 is removed.

Usually you wouldn't be connecting a 24V feed. You would be connecting a new cable/flex to the ELV terminals on your boiler.
However, there are a lot of mains operated controls on an S Plan+ system, so I don't know how you intend to mix the voltages. Is this related to the posts about X Plan systems?

Thanks. Yes, I am trying to work out whether I have everything in place in case I want to do the D-Plan or X-Plan on an Intergas boiler. But I have always struggled with any sort of electrics!

I am using the diagram uploaded by @dilalio for D-Plan where the hot water timeswitch and cylinder stat are connected to 9 & 10 on the low voltage side of the PCB. Then I thought the rest of the S-Plan+ (both CH circuits) would connect to the switched live on the 230V side of the PCB.

 

[CountryFan]

Wouldn’t it just be the grey and orange from the motorised valves that send/receive the 24v to the boiler pcb?

 

[MNW67]

Wouldn’t it just be the grey and orange from the motorised valves that send/receive the 24v to the boiler pcb?

My head's starting to spin! I get so confused by electrics. Can they send 24V. They currently have a 230V supply from the wiring centre.

 

[CountryFan]

Yes they can. Grey and orange are kind of like volt free, you apply the voltage. The actuators need mains voltage to driven the motor. So live and neutral.

Have a look at this video by @flameport
https://flameport.com/electric/central_heating/combi_boiler_2_zones_VF_1.cs4

 

[RandomGrinch]

I am trying to follow the diagram uploaded by @dilalio for D-Plan where the hot water timeswitch and cylinder stat are connected to 9 & 10 on the low voltage side of the PCB.

Yes, the LP811 could be used on the ELV pins 9 and 10.

The important point to note...

The timer would be connected in parallel with the tank stat, and you would be using the normally closed terminals I.e. LP811 terminals 1 and 2.

The diagram you mentioned for anyone else's benefit...

 

[MNW67]

Yes they can. Grey and orange are kind of like volt free, you apply the voltage. The actuators need mains voltage to driven the motor. So live and neutral.

Have a look at this video

Thanks. That all makes a lot more sense now.

So, looking at the low voltage side, would I connect the oranges and greys from the two CH motorised valves to 6 & 7 where the roomstat is currently connected.

 

[MNW67]

The timer would be connected in parallel with the tank stat

Thanks. What does in parallel mean? I thought they would go one after the other, but that sounds like in series.

 

[MNW67]

I need to say that I am not trying to do the full D-Plan or X-Plan at the moment with this design. I am just trying to work out how I might be able to trigger the boiler to give two different flow temperatures.

 

[RandomGrinch]

Thanks. What does in parallel mean? I thought they would go one after the other, but that sounds like in series.

One connected after the other, would be in-series.
The tank stat is connected, so that when it is satisfied, it will close the circuit, i.e. connecting together terminals 9 and 10 on X4.
Or put another way, with the tank up to temperature, terminals 9 and 10 are 'shorted' together.
Connecting (in parallel) the LP811 Normally closed terminals 1 and 2, to X4 terminals 9 and 10, will ensure a relatively safe way to provide this 'short circuit', when the hot water isn't required.

 

[CountryFan]

Thanks. That all makes a lot more sense now.

So, looking at the low voltage side, would I connect the oranges and greys from the two CH motorised valves to 6 & 7 where the roomstat is currently connected.

View attachment 367302

Apologies, I didn’t know about the X-plan or D-plan until I’ve just looked. They appear to use a different motorised valve, a diverter type by the look so of it, which only uses live and neutral, so I’m not sure where the 24v comes into play.

 

[MNW67]

Apologies, I didn’t know about the X-plan or D-plan until I’ve just looked. They appear to use a different motorised valve, a diverter type by the look so of it, which only uses live and neutral, so I’m not sure where the 24v comes into play.

I think you actually were right.

As far as I can work out, the pins on the low voltage side trigger the boiler to start. Pins 6 and 7 trigger CH demand and pins 9 and 10 trigger DHW demand. And crucially, as far as I can tell, when you trigger the boiler on pins 9 and 10, the boiler changes to the higher DHW flow temperature and also causes pin 5 on the 230V side to become live. Pin 5 can then be used to energise a DHW zone valve.

 

[CountryFan]

It does seem that way. Maybe this could help from Intergas? https://www.intergasheating.co.uk/app/uploads/2024/03/Ref-1_X-Plan-Leaflet.pdf

 

[MNW67]

It does seem that way. Maybe this could help from Intergas? https://www.intergasheating.co.uk/app/uploads/2024/03/Ref-1_X-Plan-Leaflet.pdf

Thanks. So that seems to be the "official" updated version by Intergas (X-Plan). It seems to use pins 11 and 12 for OpenTherm instead of standard controls on 6 and 7. But the principle of operation seems to be the same. And it shows how the DHW timer and cylinder stat are wired in parallel, so even I can grasp it!