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Thread: Evohome 2 zone, the next step.

  1. #1
    Automated Home Jr Member
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    Default Evohome 2 zone, the next step.

    Hi guys,
    Iíve had a 2 zone system running well for a year now in a new build house.
    In review I replaced the existing stats for ground and 1st with BDR91 relays.
    Main controller on Ground controls the ground relay and room stat on first controls First floor relay.
    The time controller was removed and a HW BDR91 fitted to switch HW circuit, leaving existing wiring in place for HW after this.
    The CH feed was merely connected through in the back as this is now controlled by the relays.

    So the next step is I would like to swap over one zone to being controlled Solely by H92 radiator valves.
    Can this be done by the addition of H92ís or will I need extra kit to make it work.
    Ideally Iíd like each room on the 1st floor to be totally independent so one rad can be run by itself on that floor independent of the ground floor.

    Iím electrically qualified so no issues with wiring etc, but no plumbing, so the terminology sometimes confuses.

    Any ideas?

  2. #2
    Automated Home Guru
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    Quote Originally Posted by Mr_Freeze View Post
    Hi guys,
    I’ve had a 2 zone system running well for a year now in a new build house.
    In review I replaced the existing stats for ground and 1st with BDR91 relays.
    Main controller on Ground controls the ground relay and room stat on first controls First floor relay.
    The time controller was removed and a HW BDR91 fitted to switch HW circuit, leaving existing wiring in place for HW after this.
    The CH feed was merely connected through in the back as this is now controlled by the relays.

    So the next step is I would like to swap over one zone to being controlled Solely by H92 radiator valves.
    Can this be done by the addition of H92’s or will I need extra kit to make it work.
    Ideally I’d like each room on the 1st floor to be totally independent so one rad can be run by itself on that floor independent of the ground floor.

    I’m electrically qualified so no issues with wiring etc, but no plumbing, so the terminology sometimes confuses.

    Any ideas?
    Just some clarification I presume you have Zone Valves for the Two Heating Zones and another for the HW Zone

    As far as Evohome is concerned you have a 3 Zone System

    If you have 2 Heating Zone Valves and you replaced the Stats with BDR91 are the Zone Valves Switching Boiler via their End position Limits

    IF it is as Above then Remove Upstairs Zone Valve Electrically and Physically simple way to remove physically is to remove motor head and open valve fully and leave in this position

    You now have an upstairs zone which will heat whenever Boiler Fires but Boiler now only fires if HW or Downstairs BDR calls for heat

    The upstairs BDR you have removed should be configured as Boiler Demand Relay and use this to Control Boiler Switched Live

    Now Fit HR92s to upstairs Rads and upstairs will be controlled and each HR92 will call for heat as needed and Evo will switch on Boiler Demand Relay Thus starting Boiler and circulating Heat to whichever Rad the HR92 is open on

    You Downstairs Zone Valve will now not need to switch Boiler Via End limits so you could Electrically remove the end limits as Evo will now switch downstairs Zone BDR when downstairs Stat calls for heat which will open Downstairs Valve and EVO will also switch Boiler Demand BDR thus starting Boiler so no need for Valve Limits to Switch Boiler

    HW Zone again you can remove End limits as HW BDR will open HW Valve as needed but Boiler Demand BDR will switch on Boiler instead of HW Valve End limits

    SO New Boiler Demand Relay controls firing of Boiler in all cases and HW BDR and Down BDR open respective valves and HR92s control upstairs Rads

    Its An easy conversion just some small re config in EVO Settings
    Last edited by mylesm; 6th December 2017 at 08:37 AM.

  3. #3
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    Hi Mylesm,
    Your assumptions are correct, the zone valves are indeed switching the boiler on from the position switches.
    Ok, I follow what you say and understand, but what about the radiators in each zone that have the evo (GR) and room stat(FF).
    When the FF is in demand the rad will always be on. Should I fit a rad valve on this, but what about the room stat, do I stop using this?
    FYI, the FF room stat is in the master bed along with the uncontrolled rad.
    Interestingly the boiler is an ideal logic heat 24 and when I checked the connections it doesnít have a pump overrun connection.
    I phoned Ideal and they confirmed this is correct.
    So Iím assuming when there is no call for heat the pump stops, so there isnít an issue with bypass valves?

    Your help is most appreciated.

  4. #4
    Automated Home Lurker
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    I have the same setup at the OP except that zone 1 would be the entire house minus the 2 radiators in the lounge with the second zone (obviously) being the 2 lounge radiators.

    I have set the BDR91 to control both zone valves in parallel by wiring the live from each motorised valve to the output from the BDR91. I then use HR92's to control the flow to the radiators. Seems to be working ok and I don't have to worry about needing a second BDR92 for the second zone valve. Doing this in effect turns the 2 zone system into a single zone system as both valves open and close together.

    Why the builder didn't do an upstairs and downstairs circuit is beyond my understanding, i'm sure there is a reasonable explanation.

  5. #5
    Automated Home Ninja Dan_Robinson's Avatar
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    Quote Originally Posted by Mr_Ess_Jay View Post
    I have the same setup at the OP except that zone 1 would be the entire house minus the 2 radiators in the lounge with the second zone (obviously) being the 2 lounge radiators.

    I have set the BDR91 to control both zone valves in parallel by wiring the live from each motorised valve to the output from the BDR91. I then use HR92's to control the flow to the radiators. Seems to be working ok and I don't have to worry about needing a second BDR92 for the second zone valve. Doing this in effect turns the 2 zone system into a single zone system as both valves open and close together.

    Why the builder didn't do an upstairs and downstairs circuit is beyond my understanding, i'm sure there is a reasonable explanation.
    That is a bonkers setup.
    Kind Regards - Dan Robinson (Jennings Heating Ltd)

  6. #6
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    Quote Originally Posted by Mr_Freeze View Post
    Hi Mylesm,
    Your assumptions are correct, the zone valves are indeed switching the boiler on from the position switches.
    Ok, I follow what you say and understand, but what about the radiators in each zone that have the evo (GR) and room stat(FF).
    When the FF is in demand the rad will always be on. Should I fit a rad valve on this, but what about the room stat, do I stop using this?
    FYI, the FF room stat is in the master bed along with the uncontrolled rad.
    Interestingly the boiler is an ideal logic heat 24 and when I checked the connections it doesn’t have a pump overrun connection.
    I phoned Ideal and they confirmed this is correct.
    So I’m assuming when there is no call for heat the pump stops, so there isn’t an issue with bypass valves?

    Your help is most appreciated.
    As far as I understood from your op you want all upstairs rads to be HR92 so yes master bedroom would have a HR92 you can use Existing Stat as a sensor If it is a suitable Honeywell one for that HR92 just bind it in the Zone setup if you like or use HR92 itself to sense Temp Basically upstairs has all HR92 Rads

    Gr and Evo at the moment control Zone Valve for Gr floor and stay the same zone Valve opens on Demand and Boiler fires from Boiler BDR Evo could remain as Temp Sensor for that Zone

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