That’s clear, thanks mrashton. I have no DIY or electrical skill at all, but I can follow instructions and have done a few small wiring things in the past where it’s been laid out explicitly… I will take a look at the boiler and decide whether it’s simple enough for me or I need to get someone in who knows what they’re doing…!
You need to identify the type of boiler – Combi or Conventional. Depending on what you find and the make of boiler, if a Combi, the thermostat wiring may be connected at the boiler itself. If you have a conventional boiler where you have a separate hot water storage tank, you will probably have a wiring centre attached to the wall close to the boiler that all wiring from the Cylinder Stat, Room Stat, Programmer, Valves and Boiler are connected to. If this is the system you have, and you have a single room thermostat, then you probably have the Y Plan heating layout which uses a mid position 3 way valve rather than S plan that will have 2 or more (depending on the number of room thermostats) 2 way valves.
Just look for Y Plan or S Plan wiring diagrams on the Internet which are relatively simple to understand. The wiring centre should also be wired according to a recommended standard. The 10 way Honeywell standard is often used but there are 12 way centres out there too. Once you have all of this information, wiring in the boiler switch instead of the Thermostat is quite straight forward.
Remember though that you will be dealing with 240v and the boiler/wiring centre should be isolated from the mains before you do any work and this includes the 2 wires to the Thermostat, one of which will be a 240v live feed.
If in any doubt, please call a qualified electrician to do the installation.
My set up uses the Drayton LWC1 16 way wiring centre so as you can see there are multiple different set ups out there but all are quite well documented so long as the installer adhered to the standard.
I am in the process of writing up my install. I have been away on hols, hence the delay.
In familiarizing myself with the way the LightwaveRF boiler switches and room thermostat work, I’ve uncovered something that I wasn’t really expecting, but it might be down to a misunderstanding as to where the LW920 boiler switches sit in the circuits. Let me explain through the HW circuit:
In my old boiler set up, if I turned on the HW, the HW light illuminates on the programmer display, the boiler fires up and the water in the hot water tank starts to warm up. When the hot water tank thermostat hits its target temp, it switches off the boiler, but the programmer display still shows the HW as being on (i.e. the HW light remains illuminated).
In my new LW setup, everything works the same, but when the hot water tank thermostat hits its target temp, it not only switches off the boiler, but also switches off the LW920 Boiler Switch. I assumed that the LW920 Boiler Switch would remain on.
In thinking this through, I guess the LW app is the equivalent of the old programmer display, with the LW920 Boiler Switch acting as the internal switching mechanism of the old programmer. So perhaps that all makes sense then?
A similar thing happens with the Central Heating controls.
It all depends on the wiring set up and the type of system.
In my “Y” plan set up the Boiler Switch for the CH turns on and off in the same way you describe – remember the Thermostat is an integral part of that unit for CH and is controlling whether the Boiler Switch should be on or off based on a temperature being met at the Room Thermostat.
For HW, the switch is acting as an ON/OFF relay (rather than temperature managed as with CH) with added functionality (Boost and Manual on/off and a built in Thermometer/Thermostat). In the Y plan system the Cylinder stat and the HW boiler switch work together to control the Mid point valve’s last position and whether to divert to HW and/or CH.
In my set up the HW boiler switch is ON for the duration of the time schedule when HW heating is active whether the Cylinder stat is satisfied or not.
Let me know what system you have (Y or S plan) and the wiring centre type and how you’ve configured the heating schedules.
I can’t seem to post links for some reason! And there doesn’t seem to be any way of contacting the administrator!
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