hi folks. I’m trying to install a Lightwaverf Boiler Switch on an old Potterton boiler. It does hot water to a tank and central heating. The existing old thermostat is 240V mains with four wires. Live constant, live switched (breaks when temperature drops below level set), neutral and Earth. The wiring diagrams shows the unit connected to mains and 20v thermostat terminals.
Has anyone else managed to make mains thermostat terminals work with this unit?
PS: currently got Lightwaverf link and mains/lighting sockets set up throughout the rest of the house.
Did you sort this ?
It should just be a case of disconnecting the two wires that currently go to the room thermostat and putting them on to the C and NO contacts on the boiler switch. It is effective just a relay joining two contacts together when the room thermostat calls for heat. If you are still having trouble upload some pictures of the wiring on the boiler
Hi did you ever get this sorted ? I think I have the same setup as you , I only have one one switching wire was wondering how you got around it
Hmmm, multiple people with the same question but none have returned to mention the solution
Yes – and another one here looking for the answer.
The question is, how do I control the boiler and replace the existing controller which independently controls (1) the central heating and (2) the hot water heating the hot water tank.
It looks like I may be stuck as it seems the LWRF boiler controller only turns the boiler on and off? Can I rig up something to control the valve that controls the feed to the hot water tank?
Hmm, I don’t know whats going on with this forum but whilst editing my previous reply, it disappeared completely after I submitted the edit, yet if I try and paste the reply back in, I get an error message saying its a duplicate despite no being able to see the original even after refreshing the page, closing the tab and revisiting the forum!??!
I have replaced my conventional heating controls with LWRF (I haven’t used the TRVs however).
My heating setup is a Worcester Bosch condensing boiler, a Megaflow hot water cylinder and the system is configured on the Honeywell S Plan arrangement (2 x 2 port motorised valves).
I have a boiler switch (LW920) – to control the radiators and an electric switch (LW934) to control the hot water – essentially the electric switch is just acting as a time-clock.
I have a LW921 home thermostat linked to the boiler switch. The wiring is a bit of a mair if you are not familiar with this type of thing but once working all is great. The I have time-clock settings via the app for both switches. The overall radiator temperature control is via the home thermostat and the hot water temperature control is via the original cylinder stat.
The control logic is as follows:
- Time clock settings via LWRF App (Home Stat) – on 6.30am, off 8.30am, on 4.00pm, off 10.30pm (I have slightly different times at weekends).
- Home thermostat (linked to Boiler Switch) then governs on/off demand depending on temperature.
- I have conventional TRVs on all my radiators.
- In essence – Is the heating is an on or off period (yes = boiler on, no = boiler off). Is room temperature below setting (yes = valve open, boiler on, no = valve close, boiler off).
- Time clock settings via LWRF App (Elec Switch) – on 6.00am, off 8.00am, on 3.30pm, off 10.00pm (I have slightly different times at weekends).
- Existing cylinder stat (set at 65 deg) then governs on/off demand depending on temperature.
- Elec Switch is just governing time clock settings.
- In essence – Is the hot water is an on or off period (yes = boiler on, no = boiler off). Is cyclinder temperature below setting (yes = valve open, boiler on, no = valve close, boiler off).
Check out the wiring diagrams here if you’ve not already. https://lightwaverf.com/wp-content/uploads/2015/10/LW921.pdf
Have mine working with a Worcester boiler which has a 240V control circuit to turn heating on and off (the boiler stays on). Search my other threads for details
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