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Thread: Honeywell evohome

  1. #1
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    Default Honeywell evohome

    Hello,

    I have just purchased eco home and would like some advice to install it.

    The TRVs ect I understand it’s the receivers I would like some clarification on.

    We have moved into a house with a system boiler so have a hot water storage tank and boiler. It is a pretty standard set up of a hot water tank upstairs in an airing cupboard and the boiler downstairs. The programmer/timer is also in the airing cupboard and a thermostat is located in the coldest part of the house.

    I have therefore purchased the hot water and ch evohome kits.

    I have two bd91’s am I correct that these will replace the programmer/timer? I think have the receiver to the sensor for the hot water tank which I’ll also put near there (ensuring 30cm away from each other and metal!)

    What will replace the thermostat??

    Thanks

    Victoria

  2. #2
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    A Control Panel provides overall control wherein rooms or zones are designated and schedules set up. This also connects via Wi-Fi to the internet. It can I understand be used as a thermostat itself although I have never done that.

    The TRVs - HR92s - on each radiator act as the thermostat for each room or zone, when they sense the set temperature needs to go up or down, they send a signal to the BD91 telling it to switch the boiler on. The whole system operates without a central thermostat.

    Your second BD91 as you note operates the valve for the stored hot water, the sensor telling it to go on or off as the temperature fluctuates. Again the times for this can be scheduled.

    Yes keep the BD91s and the sensor at least 30cms apart and if you can 30cms away from the hot water tank. Mine is, just!

    The app for your mobile phone gives you remote control of the whole system.

    You can, as an alternate, use a freestanding, or wall mounted thermostat, instead of relying on the thermostat on the HR92s. I use one in my lounge but generally the HR92s are adequate at controlling the temperature.

    It’s a great system. Had mine running for just over 3 years now.

  3. #3
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    It depends on how your system is configured at the moment. The most likely thing for replacing an existing system is that the 2 x BDRs will control your valves (either 2 x 2-port values, or 1 x 3-port valve), and the orange wires from the valves will fire the boiler.

    Note that if you choose to put an HR92 TRV on every radiator, you will need to ensure your system has some kind of bypass.

  4. #4
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    Quote Originally Posted by dty View Post
    It depends on how your system is configured at the moment. The most likely thing for replacing an existing system is that the 2 x BDRs will control your valves (either 2 x 2-port values, or 1 x 3-port valve), and the orange wires from the valves will fire the boiler.

    Note that if you choose to put an HR92 TRV on every radiator, you will need to ensure your system has some kind of bypass.
    Could you explain to me the bypass? I am not very technical so don’t understand the engineering side of the system. I have HR92 controllers in every room upstairs and have the whole open-plan downstairs on an evo room thermostat where each rad has an old fashioned thermostatic valve. Do the downstairs rads act as this bypass I require?

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    When a boiler switches off because the required temperature has been reached the pump will often continue to help dissipate the heat before eventually it switches off - pump overrun. If the pump is doing this it would have problems if all radiators were switched off so some sort of bypass is needed so the pump is not pushing against itself but at least providing some circulation. I don’t have a boiler with a bypass as part of the boiler or it’s installation but I have one radiator in a downstairs WC which does not have a TRV on it. This is my bypass. Always warm in there!

  6. #6
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    Quote Originally Posted by G4RHL View Post
    When a boiler switches off because the required temperature has been reached the pump will often continue to help dissipate the heat before eventually it switches off - pump overrun. If the pump is doing this it would have problems if all radiators were switched off so some sort of bypass is needed so the pump is not pushing against itself but at least providing some circulation. I don’t have a boiler with a bypass as part of the boiler or it’s installation but I have one radiator in a downstairs WC which does not have a TRV on it. This is my bypass. Always warm in there!
    Thanks. Would you know how to check if a boiler has a bypass?

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    Quote Originally Posted by duckworp View Post
    Thanks. Would you know how to check if a boiler has a bypass?
    No idea but am sure somebody here with greater knowledge of these more modern systems will step in and advise shortly.

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    ‘Google’ your boiler model along with ‘installation and servicing guide’. Most guides have a boiler schematic. Some older systems have a gated bypass ( a pipe around the pump with what looks like a stop****) rather than an automatic bypass.

  9. #9
    Automated Home Ninja Dan_Robinson's Avatar
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    What model boiler is it?

    I design systems so that bathroom rads etc, are defacto bypasses because the boilers I fit (and most modern boilers in general) have modulating pumps making auto bypasses a pita.
    Kind Regards - Dan Robinson (Jennings Heating Ltd)

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    Quote Originally Posted by Dan_Robinson View Post
    What model boiler is it?

    I design systems so that bathroom rads etc, are defacto bypasses because the boilers I fit (and most modern boilers in general) have modulating pumps making auto bypasses a pita.
    Worcester Bosch 35cdi

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