921 IQ Thermostat has a mind of its own!

LightwaveRF Community: Welcome Forums Installation and Troubleshooting 921 IQ Thermostat has a mind of its own!

This topic contains 2 replies, has 2 voices, and was last updated by  Mitchell Peplow 9 months, 1 week ago.

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     Mitchell Peplow says:

    Mitchell Peplow

    Hi all,

    New to the site so cheers in advance for any help or suggestions, much appreciated as I’m at the end of my tether with these products.

    Please see the attached picture of the setup I have to control Infrared heaters I’ve installed in two bedrooms. Note I have two Infrared heaters with their own independant 934 switches and 921 thermostats linked up to the 930 central unit. I control by both the App and Web browser but predominantly the app.

    One heater is working correctly, controlling to the temperatures and time schedule I’ve setup when in the correct mode. To be specific, when in running mode it runs to how I’ve programmed it, when I set it to Frost mode (because it’s been summer) the thermostat and heater stay off as desired. All good . . . . . until we get to the second heater.

    All seemed to be working ok because when I installed the heater we needed it to be on so I never had any suspicion that the thermostat wouldn’t work correct come summer time. With this thermostat, It has the exact same temperature and time schedule as the 1st setup, however when I put it into Frost mode via the app (which it definitely receives and acts accordingly), when the next time schedule comes around it puts it into running mode and turns on! The running man is showing but so is the frost symbol and the flame symbol!

    It does however seem to be random as to whether this happens, however for the past week it’s done it on every set schedule so it’s certainly got worse.

    The software versions are the same on both thermostats and the switches also appear to be the same.

    I do like the LightwaveRF stuff but there are some serious improvements to be made to both the hardware and the app and annoyingly when I contacted them directly they were pretty unhelpful and didn’t seem too bothered. I mean for the love of god, who decided the day starts at 6am and ends at 6pm!?!?

    When I queried this, they said I could send the unit back for the firmware to be updated to allow me to set times before 6am and after 6pm, however given it was the middle of winter I could not do this. So now I have to set it at 5:00am, then turn it off at 5:45am as you must give it a 15 minute “breather” to accept the new time of 6:00am turn on, otherwise the time schedule won’t save as it clases this as an overlap. Utterly ridiculous.

    As for the app, there has been no update since I installed it and again when I queried why some of the basic improvements had not been implemented I just got fobbed off.

    Interested to see what you guys make of this but if there is no solid resolution then I’m ripping the system out and looking for something else as the point of installing this was to same money and have control of my energy, not to waste it!



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     nevetsecirp says:


    I don’t have the electric switch LW934, but your problem intrigued me, so thought I would try and ask some questions to help etc.
    I understood you didn’t need a home thermostat to go with the electric switch, as it had its own thermostat inside it and was specifically designed for controlling electric heating systems up to 3000w
    Therefore I am not sure how the home thermostat LW921 will control the electric switch, I thought this was just controlled through the App, I also believe you can only have 1 home thermostat on a wet system, therefore could this be why you are seeing issues as only one thermostat will be working from the app.
    Have you tried removing the thermostats and just using the switches?

    LWRF light switches in several rooms, WIFI Link, Energy Monitor, Socket x3 and multiple On/Off adapters. PIR controlling lights and doorbell utilising light feature. TRV's for heating. Relays for garden and outside lamps Linked with Amazon Alexa via a dot
     Mitchell Peplow says:

    Mitchell Peplow

    Morning nevetsecirp,

    Sorry for the delayed response but I was off ill yesterday.

    You are correct in saying the electric switches have a built in thermostat, however this would mean mounting the switch in a fixed location on the wall with the power cables either being chopped into the wall or mounted in wall trunking which is not what I wanted.

    I wanted to make it look as neat and remote as possible so the switches are in the loft and all the associated power cabling then I simply have the Thermostats in the bedrooms which override the built in thermostats of the switches and the switch then does what the Thermostat tells it. Or at least it should!

    You can change the mode and setpoint via the Thermostat rather than the app if desired, it will just go back to the normal schedule at the next time change. Boost is only available by pressing it on the Thermostat, the app does not support this feature. One of the many annoyances.

    As you mentioned, you would only have one thermostat on a wet system, but if you have TRVs installed then you only need the switch and a time schedule as the TRVs dictate whats happening. I’ve also heard that the TRVs are smart and relay their position and/or current temperature back to the switch such that if all the TRVs are saying I don’t need any heat as I’m at or above the setpoint, the boiler switch doesn’t turn on. Not sure if this is true but it would make sense, assuming the TRVs relay accurate feedback position and/or current processed value.

    You can definitely have multiple thermostats and multiple switches to control individual or multiple heaters. I got LightwaveRF to confirm this before I purchased the hardware and like I say, it seemed to be working fine, it’s just this stat seems to have an issue.

    I’m going to try removing the thermostat as you say and just make sure the time schedule runs correctly with just the switch, however because these are located in the loft I wont have any control but at least it will help diagnose. I may also swap the stats around to make sure the fault follows the stat to eliminate any potential switch problem.

    I’ll let you know what my findings are.



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