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Thread: Evohome + Electric Underfloor

  1. #1
    Automated Home Jr Member
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    Jul 2016
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    14

    Default Evohome + Electric Underfloor

    Has anyone tried the new Electric Heating zone option in the controller yet? I'm just wondering if it works ok, i.e. doesn't fire the boiler when there's heat demand from that zone and only operates the BDR91/HC60NG?
    I plan to try and connect up to a new electric underfloor heating system being installed and don't want to invest in the new components unless it's all good. The electric underfloor system is being installed anyway and it would be good to integrate it with the existing wet Evohome controller.

    Also... has anyone successfully wired up Evohome with electric underfloor heating? I'm guessing I'm going to have to bodge the BDR91/HC60NG either in series with the load and UFH stat, or use it to control the power to the UFH stat itself. Doesn't seem to be any way to remove the UFH stat due to it controlling the under floor sensor for safety purposes. I think my preference is for it to control power to the UFH stat so the stat is always off unless there's a demand for heat. Makes it more user friendly otherwise family members could be trying to turn up the UFH stat and wondering why it's still cold.

  2. #2
    Automated Home Ninja
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    Mar 2017
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    Quote Originally Posted by oshingler View Post
    Has anyone tried the new Electric Heating zone option in the controller yet? I'm just wondering if it works ok, i.e. doesn't fire the boiler when there's heat demand from that zone and only operates the BDR91/HC60NG?
    I plan to try and connect up to a new electric underfloor heating system being installed and don't want to invest in the new components unless it's all good. The electric underfloor system is being installed anyway and it would be good to integrate it with the existing wet Evohome controller.

    Also... has anyone successfully wired up Evohome with electric underfloor heating? I'm guessing I'm going to have to bodge the BDR91/HC60NG either in series with the load and UFH stat, or use it to control the power to the UFH stat itself. Doesn't seem to be any way to remove the UFH stat due to it controlling the under floor sensor for safety purposes. I think my preference is for it to control power to the UFH stat so the stat is always off unless there's a demand for heat. Makes it more user friendly otherwise family members could be trying to turn up the UFH stat and wondering why it's still cold.
    Used the Electric UFH option and can confirm that it doesn't fire the boiler. Used it for a different purpose than Electric UFH so can't comment on how you'd go about wiring Electric up.

  3. #3
    Automated Home Jr Member
    Join Date
    Nov 2015
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    22

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    Using Evohome for Electric UFH.
    I’ve recently upgraded my Evohome controller to allow me to set up electric heating zones. I want to be able to schedule and control Electric Underfloor Heating (EUFH) in 3 en-suite shower rooms. In all cases, the EUFH systems are low power (450W) so can be switched directly by a BDR91. Their purpose is for the comfort of elderly folk having their early morning showers.
    The shower rooms are heated by Evohome-controlled wet towel rails, and a couple have no Evohome control – they are in a bypass circuit when the original heating system was installed in 1991. (I believe this is to dump heat if the boiler is on but all other system rad valves are shut.)
    Each EUFH element is connected to the mains via a simple “Warmup” brand “mstat” switch/thermostat. This device is connected to an underfloor temperature probe, and has a simple, old-school physical dial to adjust the set temperature. It also has a mains on/off switch. Its simplicity and lack of electronic configuring is good, because the plan is to supply mains to it via a BDR91 – and it’s important that the Warmup device doesn’t reset after a mains re-start.
    Initially I set up the Warmup thermostats to give a comfortable floor temperature.
    Next, I connected each Warmup device to the switched output of a BDR91.
    Then I installed a Honeywell Y87RF2040 wireless room thermostat in each shower room.
    For each room I set up a electric heating zone, with the Y87RF2040 as the temperature sensor and the corresponding BDR91 as the EUFH actuator.
    I adjusted the set temperature of each EUFH zone to be 24C – a temperature the rooms rarely attain – certainly during winter.
    Hey presto – Evohome control of the EUFH! The BDR91 switched on when called upon and stayed on so long as the air temperature stayed below 24C. The Warmup stats allowed me to adjust the floor temperatures.
    So far… so good!
    But – can you spot any problems? Well – Evohome’s Optimization feature (which I love) is a problem with my EUFH.
    Optimization is an all-zone setting – so it is “on” for all the EUFH zones as well as the wet central heating radiators. (I wish I could enable it zone by zone!)
    Suppose I set the first “on” time for a EUFH zone to be 6:00a.m. With Optimization enabled, Evohome switches the EUFH “on” at 5:00a.m. and waits, in vain, for the Y87RF2040 to reach 24C. All this time the Warmup stat is controlling the UFEH element.
    Realising that 1 hr is not long enough to get the zone to temperature, the next morning, Evohome gives an even longer optimization time… and so on.
    What I want is for the zone to switch on at 6:00a.m. In effect I want to disable the optimization for the UFEH zones.
    My current solution (and it’s still very much a work in progress) is to set the schedule for an UFEH zone to be 5C for 3a.m. … and 5C for 4a.m. … 5C for 5a.m. and 5C for 6:00a.m. and 25C for 6:30 a.m.
    I’m hoping this will stop Evohome’s otherwise excellent optimization feature from switching on the EUFH prematurely. I’m hoping it will, in an attempt to get the temperature to 25C by 6:30a.m., switch on at the earliest opportunity, which, being constrained by the 3a.m. 4a.m. and 5a.m. settings, will be 6:00a.m.
    I’ll keep you posted, and would welcome any comments on this idea.

  4. #4
    Automated Home Ninja
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    I think personally I would turn optimum start down to 1 hour max, and then adjust your zone settings to come on at a later time with the intention of it coming on an hour earlier.

  5. #5
    Automated Home Jr Member
    Join Date
    Nov 2015
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    Sounds like a good plan mtmvgavock. Ill press on with my plan for a couple more weeks - mainly to see how long before the scheduled start times my regular heating zones fire up on a winter morning - to see if 1 hour is enough. Then will try your idea for a few weeks and make a choice.

  6. #6
    Automated Home Ninja
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    Personally I found that anything more than an hour was too much for me. It was bringing radiators on 2 hours before the required time when in reality it didn't need to, however that was in the initial learning stage so it would have adjusted over a few weeks. I found that an hour was the sweet spot, and due to my environment (Well insulated house etc.) that an hour is plenty.

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