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Thread: CM Zone Questions

  1. #1
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    Default CM Zone Questions

    Hi, have just bought a CM Zone Pack (1 x CM67Z and the boiler relay), and an extra pack of 4 x HR80UKs

    I already have a CM927 and DBR91 combo controlling my boiler.

    1....I'm thinking I may be able to reuse the CM927 to act as the temperature sensor in a zone in which 2 of the radiators are in cabinets (my large dining room), and the 3rd radiator (uncased) is at the bottom of an open staircase tha leads into the same dining room. Is that a sensible use of the CM927? i presume it will be the temperature sensor for all 3 radiators in such a scenario? Or can I have i such that the 3rd radiator's HR80UK uses it's own temp sensor?

    2...The CM67Z (i believe) can also act as temperature sensor? The kitchen has 1 radiator exposed, and 1 hidden behind the sink, and vents through the workop (not very efficient I know, but it's what I inherited when I bought the house). So i presume i could use the CM67Z sensor to sense the temperature in the kitchen zone? Same question as before - will the exposed radiator HR80UK be able to verify it's own temperature in such a scenario?

    3....I have an area - large hall, staircase and landing - that has 4 rads. As I don't have enough HR80UKs for all the house rads, I thought I could run this area with another CM67Z (if I buy one) to monitor the temperature, and run conventional TRVs in this area until such time as I get more HR8OUKs. I'm thinking if it gets cold enough, the CM67Z in this are will kick the boiler in and warm the area up, while if it is up to temperature, but a different zone is causing the boiler and pump to run hot water round the circuit, the TRVs will limit the heat output in this area to their setpoint?

    4..... I understand the DBR91 is newer, so presume I'd continue to use that, over the one that comes in the CM Zone pack (HC60 or something?).

    5.... I understand I can parallel boiler relays in future if I need to. But does that not run a risk of running the boiler for more cycles than is set up in the controls?

    Grateful for any advice as new to this setup, and have found the threads on here very useful in my research, so have joined today!

    Simon

  2. #2
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    6.... Am I better off ebaying my existing cm927 and the new CM67Z and buying an evotouch unit instead? The advantage would seem to be 8 zones under control with the Evotouch, the disadvantage would be I couldn't use the in built temperature sensors of the CM927 and CM67Z in those areas where the radiators are in cabinets (assuming I can do that in the first place) (and it would cost me more). Simon

  3. #3
    Automated Home Sr Member MichaelD's Avatar
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    Google can't find any mention of a DBR91, so no idea what that is. Can it be controlled by CM zone systems? That is the critical question for your Q4

    You do have the choice to use the temperature sensor in the HR80 or the one in the CM67z, but not both.

    Q5 question only matters if you want to use the CM zone kit to stop boiler cycling. If you have a good modern boiler, that will take care of its own cycling, so you don't need to worry about how you control it externally.

    You can design the heating control system to use multiple systems, but it is then pretty complicated, but perhaps that is half the fun. Basic TRVs just apply an upper limit to room temperature, I use some mixed with HR80s, so the basic control is on when the boiler is running, the HR80 can be on or off depending on time and temperature. The ideal set-up is obviously HR80s on every radiator, but that does get v.expensive.

    For me, the CM67z is a good, local controller, I have four of them running two rooms each. They are mounted outside the rooms on the wall, so its easy to adjust the temp before you go into the room. Centralised systems like the Evotouch have you running to the central location, or kneeling down and squinting at the dial on the HR80.

  4. #4
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    Quote Originally Posted by MichaelD View Post
    Google can't find any mention of a DBR91, so no idea what that is. Can it be controlled by CM zone systems? That is the critical question for your Q4

    You do have the choice to use the temperature sensor in the HR80 or the one in the CM67z, but not both.

    Q5 question only matters if you want to use the CM zone kit to stop boiler cycling. If you have a good modern boiler, that will take care of its own cycling, so you don't need to worry about how you control it externally.

    You can design the heating control system to use multiple systems, but it is then pretty complicated, but perhaps that is half the fun. Basic TRVs just apply an upper limit to room temperature, I use some mixed with HR80s, so the basic control is on when the boiler is running, the HR80 can be on or off depending on time and temperature. The ideal set-up is obviously HR80s on every radiator, but that does get v.expensive.

    For me, the CM67z is a good, local controller, I have four of them running two rooms each. They are mounted outside the rooms on the wall, so its easy to adjust the temp before you go into the room. Centralised systems like the Evotouch have you running to the central location, or kneeling down and squinting at the dial on the HR80.
    Sorry that should have read BDR91. The receiver replaces the HC60NG I believe and thus I could use in preference to that supplied in the CM Zone pack I guess which would save me a few mins work.


    If I used two receivers in parallel, each would have their CPH set from their respective controllers - that was what I was concerned about, so are you saying that is irrelevant as the boiler manages that itself and ignores the controller anyway? my understanding was that the receiver(s) collated the energy demands from the various stats and managed the demands to the boiler based on the the CPH parameters you have set in the CM67z. If you have two receivers in parallel, you could potentially have two lots of 6CPH demands being sent to the boiler, unsynchronized, so potentially 12 CPH. But the boiler would just ignore?

    I did have a brainwave in that I have 16 rads, 14 HR80s and 3 towel rads. I thought the 2 main rads in my dining room, I could leave with TRVs and manage with my cm927 as a room stat (the rads are in covers). But then realised that they'd get heat whenever any hr80 was demanding heat elsewhere, which could be quite wasteful. Think i'll get two more HR80s so they can properly shut down when not required.

    Having got the hr80s was a bit disappointed at the plastic gearing - what is their life like?

    Simin

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