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Thread: Questions after configuring my FHT-80b system

  1. #1
    Automated Home Jr Member
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    Default Questions after configuring my FHT-80b system

    Hi all,

    I've had a controller and pair of valve for a while but only just got round to configuring them. I have a couple of questions after this:

    With the required temperature set to 30, the 2 valve indicate they are at 68% open. Given 30 degrees is a lot higher than the current room temperature I would have thought this should be 100%?

    The control unit had an initial security code, as did each of the radiator valves (all different). I was expecting to program each valve code to the control unit however it looks like what has actually happened is all 3 security codes have been programmed to the same code. Is this expected? The units appear to be working so I'm not too concerned but would be interesting to know.

    The valves comes with 3 different adaptor rings for various Danfoss TRVs. I currently have a Honeywell (VT117) TRV which I can screw directly onto the conrad valve (without having to use any additional adaptor). Is anyone using Honetwell valves / does this seem correct? (I need to install TRVs on all my radiators and want to check I get the right type).

  2. #2
    Automated Home Jr Member
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    Quote Originally Posted by phoenix View Post
    With the required temperature set to 30, the 2 valve indicate they are at 68% open. Given 30 degrees is a lot higher than the current room temperature I would have thought this should be 100%?
    I am not sure exactly why the FHT-80B seems to be slightly inconsistent between different devices. The actuator in my dining room never seems to open 100% even when I set it to 30C. I have also noticed that on some devices the actuator stays open even once the temperature has been reached - this morning in my bedroom (set to 20C) the actuator was still 20% open when the temperature had reached 22C. This was as monitored on FHEM.

    Quote Originally Posted by phoenix View Post
    The control unit had an initial security code, as did each of the radiator valves (all different). I was expecting to program each valve code to the control unit however it looks like what has actually happened is all 3 security codes have been programmed to the same code. Is this expected? The units appear to be working so I'm not too concerned but would be interesting to know.
    I think this gets corrected as part of the set-up when the actuators are in programming mode.

    Quote Originally Posted by phoenix View Post
    The valves comes with 3 different adaptor rings for various Danfoss TRVs. I currently have a Honeywell (VT117) TRV which I can screw directly onto the conrad valve (without having to use any additional adaptor). Is anyone using Honetwell valves / does this seem correct? (I need to install TRVs on all my radiators and want to check I get the right type).
    I use Pegler valves on my system and the actuators connect directly to them in the same way with no adapter.

  3. #3
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    Thanks for the info autolog ... now to get the CUL USB device.

  4. #4
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    Quote Originally Posted by autolog View Post
    I am not sure exactly why the FHT-80B seems to be slightly inconsistent between different devices. The actuator in my dining room never seems to open 100% even when I set it to 30C. I have also noticed that on some devices the actuator stays open even once the temperature has been reached - this morning in my bedroom (set to 20C) the actuator was still 20% open when the temperature had reached 22C. This was as monitored on FHEM.
    Just to add a bit more to this, I have a suspicion that the FHT system is being "intelligent" - in other words, it's trying to work out things like how long the room takes to heat up and how quickly the room loses temperature. What should definitely happen is that the device actuator stays open when the room is at the required temperature, and therefore as the temperature goes above the required temp, the actuator will still be open, just to a much lesser percentage.

    Having said all of the above, I have on at least one occasion found a situation where the FHT80 stopped sending out actuator messages for a few hours, with the effect that the actuator stayed at 100% while the room temperature rocketed to about 25 degrees! I guess you can try to the "STEL" feature in the FHT80 controller's setup menu to investigate if this is happening in your case?

    Russ

  5. #5
    Automated Home Jr Member
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    I would agree with this. The FHT80b seems to open a bit, wait, see what happens and open a bit more, stay the same or close a bit and wait again.

    When I first purchased the system, I had no FHT8W controlling the boiler so during the day, the heating was off. Looking at the graphs I was drawing from FHEM, I could see the actuator open a bit, wait, realise the room wasn't getting any warmer (because the timer on the boiler was off) then open the valve a bit more and wait again. I guess the reason for this is that radiators are not very responsive - we are pumping hot water through them to heat the metal and this takes some time to warm up and cool down. If the valve were opened to 100% straight away, the radiator temperature would shoot up and continue to pump heat into the room even when the valve is closed so you would get huge peaks and troughs and not a nice controlled heat that the system tries to provide.

    I would also agree that if you are at all concerned, check the STEL reading on the 80b and check that the 8v's say the same.

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