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Honeywell st9100c/CM707 (replacing with Hive dual channel)

Discussion in 'Plumbing and Central Heating' started by morley81, 4 Sep 2020.

  1. morley81

    morley81

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    I need a help here, please.

    I have a Honeywell ST9100C that controls 2 zones and hot water tank. The zones have CM707 thermostat.

    The objective is to replace these by Hive. I have one dual channel and one single channel in hands.

    Checking the back of ST9100C I got confused on how to connect both receivers.

    I asked (wrongly, sorry) on other thread about it and got a reply from @stem that I should link 1 and 4 on the dual channel receiver.

    But how should I wire the single channel? I draw what I need to do up to here. Hope you guys can help me.
     

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    Last edited: 4 Sep 2020
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  3. stem

    stem

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    The Honeywell ST9100C is just a single channel timeswitch [provides on & off control only. Terminals 1 & 4 are the switch] so usually that is only wired to control the hot water on and off times and has no control of the heating.

    The CM707 is a programmable thermostat, ie one that provides both time and temperature control in one unit, as you have two, one will probably be for the living areas and the other for the sleeping areas. I'm guessing you are in a new build as recent building regulations require the provision of different time and temperature control of the two areas as an aid to saving energy.

    If this is correct, then it's what you want to do is not easy. You will need to be electrically competent and have a full understanding of how the heating system is wired and works.

    1) The dual channel Hive receiver replaces the ST9100C and the Hot water motorised valve live connects to Hive terminal 3 [Hot water on] via the hot water cylinder thermostat.

    2) Then the control from one of the CM707's for a heating motorised valve will need to be rerouted to the dual channel Hive receiver terminal 4 [Heating on]

    3) Finally the single channel Hive replaces the remaining CM707, but as the CM707 is battery operated and the Hive receiver is mains powered you may find that you have to install a new 230V supply from the same 3A supply as the boiler as well, and then another issue is do you want a Hive receiver visible on a wall where one of the existing room thermostats is located? If not, then the wiring will need modifying to locate it elsewhere.

    If I was installing this I would start again and wire it up from scratch, it's not a straight swap of a couple of components I'm afraid.
     
  4. morley81

    morley81

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    Thanks for this.

    I was sure something was missing to wire it correctly.

    It looks like I’ll need assistance.
     
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  5. morley81

    morley81

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    Let's say I had some spare time today.

    I draw the wiring how it is and how it should be after install Hive over the 2 zones.

    Am I correct on the understanding after read what you wrote a couple of times?
     

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  6. stem

    stem

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    I've had a quick look and not a lot makes sense unfortunately, and it's wrong on many levels I'm afraid.

    Only the Single channel Hive seems to have a mains supply to N and L. All the rest of the components with the exception of the Zone 2 valve which is connected to it, don't have any power supply to them. And the Zone 2 valve wouldn't work anyway as it doesn't have an neutral connected to an actual incoming neutral.

    There also seems to be a blue wire (neutral?) just between the pump and HW motorised valve, but neither are connected to an actual neutral so neither the pump or the motorised valve would work.

    All neutrals should be connected together [ie 3 x motorised valves, boiler and pump (unless the boiler has separate dedicated pump terminals more on this later)] and to an incoming supply neutral.

    None of the terminals on any parts are labelled so who can say if they go where they should.

    The Hive Dual Channel hot water live output [terminal 3] should go to the hot water cylinder thermostat, but I don't see it anywhere, and then to the HW motorised valve, but it goes instead to the "boiler thermostat"

    Also what is "boiler thermostat"? There wouldn't be any connections to be made to the boiler thermostat, that is an integral part of the boiler control circuitry so wouldn't be any external connections to it whatsoever. I assume this is the boiler.

    Also, most boilers control the pump directly from their internal PCB and have dedicated pump connection terminals for it. Not all, but you haven't given any details so I can't say, and if the pump isn't controlled by the boiler it would be connected to the same switched live and neutral as the boiler. Which it isn't.

    On a plus point, terminal 4 from the dual channel hive goes to heating zone 1 motorised valve and provided it's connected to the motorised valve's live wire that's correct, and terminal 3 from the single channel hive goes to heating zone 2 motorised valve and provided it's connected to the motorised valve's live wire that's also correct.

    You also have all of the motorised valve orange wires connected together, which is right but they don't go to the boiler which they should.

    The basic concept is:

    Hive dual channel terminal 3........>hot water cylinder thermostat......>hot water motorised valve live supply
    Hive dual channel terminal 4........>Zone 1 motorised valve live supply
    Hive single channel terminal 3........>Zone 2 motorised valve live supply

    Both Hives, require L & N from the same 3A fused supply as the boiler [note, not all boilers require a permanent live but most do]

    Same neutral connection to all 3 motorised valves and boiler

    The orange and grey motorised valve wires control the boiler, so all grey MV wires are connected together to a permanent live and all orange MV wires are connected together to provide the switched live to fire up the boiler. So when any of the motorised valves is open, the boiler starts up.

    It's not simple I'm afraid and can be costly to resolve if you get it wrong, from what you have posted, personally I feel you don't understand how the system works and would recommend that you engage the services of a professional to do this for you.
     
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  8. morley81

    morley81

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    Stem, I'm sorry I mistaken the name of the HW cylinder Thermostat.

    At the water tank, where are the MV, the three zones have labels and I traced the wires from the MV. So I was able to do the diagram based in what I found.

    I knew that black loose cable on the drawings should go to somewhere. To the boiler.

    I'm not touching or rewiring everything, I just draw to understand how it is wired. Clearly I don't have full understanding of the system, but I'm curious.

    At the first sight on the back of ST9100C I notice more wires were required to make the system works. Now I know they are what you mention as "Hive dual channel terminal 4" and "Hive single channel terminal 3" above. Everything else is on its place and how it's supposed to be.

    I corrected the drawing and marked in red the new wires that I need.
     

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  9. Johnmdc

    Johnmdc

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    That all looks good. Only thing you've missed is the neutral and earth to the boiler.
     
  10. stem

    stem

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    That's better. The links added between the terminals complete the missing connections.

    I see the boiler is also shown now, and as @Johnmdc mentions, I guess that the mains supply to it is there but not shown. [The whole system should be supplied via the same 3A fused connection unit]

    The cylinder thermostat is just a simple on/off switch that operates the motorised valve when hot water is required, so normally with an S-Plan, only the two live wires go there (one from Hive 3, and one to the MV which you show). You also show a separate 230V supply connected to it, which would be a bit unusual, unless yours is an uncommon type, or wireless version that requires a 230V supply to provide it with operating power. Which I suspect may be the case as you show it is already installed like this.
     
  11. morley81

    morley81

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    Hi guys,

    I didn't trace the wires to the boiler at the first moment. Yesterday I opened the wiring box again and it's how you mentioned above.

    The Hive is installed. The dual channel receiver is installed and working, I'm waiting the second one arrives. I took longer to pair it to the hub than to run the new wires.

    Thanks for all the review and support here.
     
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