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Thread: UFH - EvoHome and reluctant plumber

  1. #11
    Automated Home Jr Member
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    Yes it was rvb99's first approach that best fitted my situation as the manifold came with electric actuators. I totally agree about the sense in keeping manifolds, pumps and wiring centres accessible and I had the luxury of siting it in a full size cellar beneath the space in question. Only problem was that the boiler is three floors above necessitating a long heat shielded connection via the CH pipework. Evohome was fitted some time after the UFH was installed. The floor is flagged so it took a bit of juggling with the schedule but now the spaces concerned are consistently dead right.

  2. #12
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    if the entire manifold is serving one heating zone, then electric actuators are completely unnecessary. They are only needed if individual runs are serving different rooms, which can be shut off from others..

  3. #13
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    I have a single zone twin loop UFH setup controlled via Y87RF and BDR91 in my new well insulated extension. BDR91 activates the pump and manifold valves are left open.

    As itís in combination with 26 rads, there is a thermostatic mixing valve to reduce the flow temperature. Boiler is Intergas HRE40 SB with OpenTherm module, and an outdoor sensor (unfortunately weather compensation doesnít work with Evohome OpenTherm support though).

    Iím not happy with the UFH setup for a few reasons:

    1. The mixing valve intermittently emits a high pitched whine, appears to be when the flow temperature matches its set point.
    2. Wife complains about 1!
    3. Poor temperature control. Evohome indicates a 40-60% demand for the zone even when the set point is reached, as a result there is an overshoot. Optimum start typically pre-heats for 1.5 hours, temperature increases to more than 1 degree above the set point after a few more hours, still with <20% demand, then optimum stop kicks in 1 hour before set back. Iíve tried reducing the mixing valve set point temperature but Evohome seems unable to adapt.

    Primarily because of 2, Iím going to replace with an HM80 controlled rotary actuator and flow temperature sensor. I hope this will work better with OpenTherm and provide more accurate temperature control.

  4. #14
    Automated Home Sr Member
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    Im not sure fitting flow sensors and HM80 actuators will make much difference. The ufh pipes are run at fixed mixed temp or they are off. The heat regulation is a function of evohome turinÓg the ufh unit and actuators on or off at set times. The manifold temp should be set such that the floor surface never gets above around 26-28 deg and the difference between in and out manifold temps are around 5-10deg . One of the issues with ufh is that it takes a long time to lean the heating requirement, because of the slow heat latency ( eg so no point tryÓg to
    set a very low night temperatures) . The other ( although this is my speculation ) is that there is a little more intelligence in the bespoke HCC80 ufh controller rather than the simpler BDR91 , the pricer former set to better control some of the above deficiencies. We get a few overshoots with the HCC80 but this is on one zone with a lot of south facimg glass. Hence if the room is at temp and we then get 3-4 hours of sun it takes a while to get back to target temp.
    Last edited by rvb99; 26th February 2019 at 07:07 PM.

  5. #15
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    I would only get the HCC80 if ever there was a need to split a single manifold into multiple zones.

  6. #16
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    The HM80 is a fuzzy logic controller, so I am hoping it will offer better temperature control for a single zone UFH, than BDR91 TPI, just like you see with the HCC80.

    https://ensupport.getconnected.honey...language=en_US

    It will be a while before I know though, as it is on back order with Honeywell via the Evohomeshop.

  7. #17
    Automated Home Ninja
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    Run 3 UFH separate zones off BDR91s and have no issues with them, temperature control is just fine. IMO the HCC80 is a waste unless you have 5+ zones.

  8. #18
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    What schedule and set points are you typically using for your UFH zones? Are you combining with rads via a lower temp mixing valve? Using OpenTherm?

  9. #19
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    Quote Originally Posted by kevinsmart View Post
    What schedule and set points are you typically using for your UFH zones? Are you combining with rads via a lower temp mixing valve? Using OpenTherm?
    Fot us we only have a day and night setting for the ufh zones. We have 14 radiators in the system controllered by HR92s ( some in groups using Y87RF
    sensors ) . No open therm. Input temp to ufh mixing sysyem 65-70 deg Manifold output temp approx 45deg. Manifold return temp approx 38deg. HCC80 ufh controller , operating 2 zones with 7 pipe runs of 80 Metres. However each set up is goÓng to vary quite a bit. If pipe length are similar it makes settÓng up of the flow rates easier to get to the in/out temp differentials. We also have a separate safety thermostat attached to the manifold output set to shut down the whole ufh system if it gets to 50deg. This is to protect the floor but also for health issues. Too high ufh temp can be bad for some peopleís circulation.
    Last edited by rvb99; 26th February 2019 at 08:58 PM.

  10. #20
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    Quote Originally Posted by kevinsmart View Post
    What schedule and set points are you typically using for your UFH zones? Are you combining with rads via a lower temp mixing valve? Using OpenTherm?
    Runs 24/7 during the winter at 21oc, Spring/Autumn it drops down a couple of degrees at night to 19oc. Mixture of UFH and rads. Manifold with mixing valve set to around 60oc. We have had it lower before but prefer a warmer floor so run it higher. Not on opentherm, boiler flow at 70oc.

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