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Thread: Worcester Bosch Heatronic 3 - FW100 controller

  1. #1
    Automated Home Lurker
    Join Date
    Jan 2014

    Default Worcester Bosch Heatronic 3 - FW100 controller

    Greetings forum, I've just joined!

    A couple of months ago I had a new system put in with a WB 28CDi Compact boiler. I wanted a reasonably smart controller that took into account the external temperature and I went for the FW100. This is my first radiator system, previously I had storage heaters so was always keeping a weather eye out.

    I'm beginning to realise the FW100 isn't as smart as I thought and find I'm constantly adjusting the TRVs depending on what I'm doing and time of day. So I've been looking at alternative controllers but nothing seems to work with the Heatronic 3 enabled boilers. I realise I could use something that just acted as an on/off thermostat, but that would be defeating the purpose of the throttle in the boiler the FW100 uses to adapt to external conditions.

    Anyway, while I was waiting for my account to be enabled I was doing some more research and am now thinking about a Z-Wave based controller driven from my NAS box to control some wireless TRVs. So far I've narrowed it down to Aeotec Z-Stick, OpenRemote running on the NAS box and some Danfoss Living Eco Digital TRVs. The idea is eventually I may be able to dispense with the FW100 and have a Z-Wave thermostat, but I'm hoping for something that knows about Heatronic 3.

    I'd be very interested to hear any thoughts and experiences others have had in this area.


  2. #2
    Automated Home Jr Member
    Join Date
    Dec 2013


    I'm assuming that the FW100 is a weather compensator?

    I had a new Vaillant combi boiler installed about 3 years or so ago to replace an ageing 30+ year gravity based system. At that time, I was using the HouseHeat / ELV / Conrad FS20 based thermostats, radiator valves and boiler interlock to great effect, but I was persuaded by the gas installer to remove it all and fit the Vaillant weather compensator instead. What a bag of poop that was :-(

    As a family we just couldn't get on with it, the heating seemed to be on nearly all the time, like coming on "gently" at 3am just so that by 7am when the schedule was supposed to kick in it was "warm" for the hour we have the heating on in the mornings. Or refusing to come on at all, even though the house felt chilly. I understand the principle of weather compensators and I persevered with it for a couple of months before finally removing it and re-fitting my previous solution :-)

    I've been migrating most of my HA systems over to Z-Wave during the past few years, so I'll be attacking the heating again at some point in the near future - the FS20 based stuff is ok, but has it's own limitations and issues.

    Your idea above sounds doable, but I would be tempted to go for StellaZ valves over the Danfoss. The Danfoss have local control and a nice LCD display but they *don't* report the temperature back to the Z-Wave network, which might be a requirement if you need that sort of data and don't have it from elsewhere. They also react quite slowly to changes - you adjust the setpoint temperature and the Danfoss will s-l-o-w-l-y adjust itself to that temperature - this might be a consideration if you want to be able to react quickly, for example shutting off a radiator when a door or window is opened. The StellaZ don't have local control or display, but do report the temperature and react quicker to commands.

    Food for thought?
    Martyn Wendon
    Check out my Blog!

  3. #3
    Automated Home Lurker
    Join Date
    Jan 2014


    Yes, the weather compensator. It did take quite a lot of tweaking and a long phonecall with WB support people to get a useful setup. They said the default settings are designed for a typical German home, but since it was purchased in the UK you'd have thought they would have loaded different defaults. It does obey the settings and doesn't come on at odd hours, although the first coldish night the pump started running at full blast for no apparent reason. I tracked this down to a frost protection system in the FW100, separate to the boiler's own protection system. It seems that if the outside temp drops below a preset value (+5degC) it will run the pump. Fortunately you can change the setting, so it can be much lower if you have no vulnerable pipes outside the main heated building.

    Thanks for the tip about using StellaZ, I'll look into that. I was attracted to the Danfoss because it has a standalone display and control in case my plans go awry.

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