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Thread: Evohome UFH question

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    Default Evohome UFH question

    I have an Evohome install with all rads fitted with HR92s (9 in total). The boiler is a Potterton Ideal 50 as a sealed system with Megaflo for HW and all radiators on the same run of pipework.

    We are planning a kitchen renovation and one option I'd like to explore is to replace the existing rad with a wet UFH solution. From reading, it seem important (due to the flow temperature requirements) that the UFH and rads can be independently controlled.

    My simple question is would adding a wet UFH system to my exiting rad pipework in place of the kitchen rad, with a HCC80R work (assuming that all the other rads remain controlled by HR92s so that the UFH would be able to call for heat independently of the rads when required)

    Apologies for the naive question but my Honeywell installer is proving difficult to get hold of at the moment

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    UFH needs a seperate blended temperature circuit, job for an experienced installer
    I work for Resideo, posts are personal and my own views.

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    As above, its a seperate circuit. You can't use boiler or radiator temperature water in UFH.

    You have a manifold to control the temperature flowing round the pipes in the underfloor. They look like this:

    manifold.jpg

    At the bottom left you will see a white temperature control, this is where the flow and return to the boiler fit and the temperature of the water flowing round the underfloor part is controlled. The seperate pump you can see here then pushes water round the flow and return rails (orange and white heads in this picture) and controls the temperature by taking only the heat it needs from the boiler flow and return.

    The HCC80R controls this manifold, opening and closing valves to relevant zones (if you have more than one zone on the manifold).

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    Quote Originally Posted by Cchris View Post
    As above, its a seperate circuit. You can't use boiler or radiator temperature water in UFH.

    You have a manifold to control the temperature flowing round the pipes in the underfloor. They look like this:

    manifold.jpg

    At the bottom left you will see a white temperature control, this is where the flow and return to the boiler fit and the temperature of the water flowing round the underfloor part is controlled. The seperate pump you can see here then pushes water round the flow and return rails (orange and white heads in this picture) and controls the temperature by taking only the heat it needs from the boiler flow and return.

    The HCC80R controls this manifold, opening and closing valves to relevant zones (if you have more than one zone on the manifold).
    For a single UFH zone you can also use a 'mixed' UFH circuit with mixed circuit controls (ideal when you have a radiator circuit at a higher temperature and want a much more accurate temperature control of an UFH circuit). The evohome system even has a mixed circuit controller that we sell (HM80) just for this particular job. This is normally a professional installers job as the flow rate for the UFH circuit needs to be calculated, mixing valve and actuator correctly sized, etc but certainly there are more (accurate) control options available for UFH control of a single UFH zone than a fixed UFH blending valve.

    Look at page 20 of the old evotouch Application Manual for a diagrammatic overview of a mixed UFH circuit - http://www.honeywelluk.com/Documents...ion_Manual.pdf

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    I'm in exactly the same position as the OP. With the exception that the boiler is a Valliant. My installer, who has done previous UFH installs, does not know evohome. My question is how does the HCC80R call for heat from the boiler? Is it to be hardwired or will it operate via a BDR91? If the latter will it trigger the existing central heating BDR91 or will I need a new BDR91? I know that the installer will be connecting the pipework for the HCC80R to the boiler prior to the zone valves for the CH and HW.

    Thanks for any insight you can give.

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    Quote Originally Posted by philipW99 View Post
    I'm in exactly the same position as the OP. With the exception that the boiler is a Valliant. My installer, who has done previous UFH installs, does not know evohome. My question is how does the HCC80R call for heat from the boiler? Is it to be hardwired or will it operate via a BDR91? If the latter will it trigger the existing central heating BDR91 or will I need a new BDR91? I know that the installer will be connecting the pipework for the HCC80R to the boiler prior to the zone valves for the CH and HW.

    Thanks for any insight you can give.
    Depending how evohome is configured both options are possible with the HCC80R. The BDR91 'boiler relay' approach is my preferred approach. How is your current BDR91 being used? With evohome or another Honeywell thermostat?

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    Thanks for the advice. Existing config is 1 BDR91 for HW (coupled with a CS92 sensor) and a further BDR91 for the CH system which has 9 HR92 valves/sensors on the radiators. Its an S plan system. So, should I bind the HCC80R to the existing BDR91 for the CH system? If I do then it will open the zone valve for the CH when the UFH calls for heat. Is that OK? Or should I have a new BDR91 bound to the HCC80R that will trigger the boiler but not the zone valve.

    Thanks again for your input.

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    Quote Originally Posted by philipW99 View Post
    Thanks for the advice. Existing config is 1 BDR91 for HW (coupled with a CS92 sensor) and a further BDR91 for the CH system which has 9 HR92 valves/sensors on the radiators. Its an S plan system. So, should I bind the HCC80R to the existing BDR91 for the CH system? If I do then it will open the zone valve for the CH when the UFH calls for heat. Is that OK? Or should I have a new BDR91 bound to the HCC80R that will trigger the boiler but not the zone valve.

    Thanks again for your input.
    No need to bind HCC80R to anything other than evohome when prompted at the correct time through 'ADD ZONE' (see page 24, 25 & 26 of the evohome Installation Guide). In your above configured situation, the Heating Motorised Zone Valve will open when there is UFH demand.

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    Hi guys, this might be correct thread but I am not sure. I have a question:
    Is it possible to add an HR92 to a zone controlled by Honeywell Underfloor Heating Controller HCC80R? Literally I want to install a radiator in the kitchen heated by wet underfloor system. I need this to boost performance of underfloor system, as in cold weather I donít get enough output. Thank you in advance.

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    Quote Originally Posted by Stan View Post
    Hi guys, this might be correct thread but I am not sure. I have a question:
    Is it possible to add an HR92 to a zone controlled by Honeywell Underfloor Heating Controller HCC80R? Literally I want to install a radiator in the kitchen heated by wet underfloor system. I need this to boost performance of underfloor system, as in cold weather I donít get enough output. Thank you in advance.
    Have you tried increasing the ufh mixing ( manifold ) temperature . You can usually increase to around 45-50deg , still keeping the floor temp itself to the max recommended 26-27deg. Also check the flow/s for the hydraulic circuits. As a rough guide they should be the loop length / 40. Eg 80m loop should be 2-2.5 litres/min. This is a good link for rule of thumb calculations http://www.heatweb.com/techtips/Underfloor/underfloorheating.html
    Last edited by rvb99; 21st March 2018 at 09:15 PM.

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