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Honeywell T6160B to CM907 Room Stat, Some Problems? Updated

Discussion in 'Plumbing and Central Heating' started by smarty, 16 Oct 2008.

  1. smarty

    smarty

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    I posted a couple weeks back on here about problems with my central heating pump and 3-way zone valve not opening when I selected heating on my programmer, but the boiler was starting. So after some great advice off cjb1971, I linked out the red and yellow wires on the wall thermostat (Honeywell T6160B), this started the pump and opened the 3-way zone valve. So I decided to get a new wall stat and went for a digital Honeywell CM907 7 day timer hoping to have better control of the heating, i.e. just leave the programmer on all the time and let the wall stat control when the boiler, zone valve and circulating pump started. I wired the CM907 as shown on the wiring diagram.
    [​IMG]
    Red live wire to pin B, and yellow wire to pin A. And taped up the redundant blue wire.
    My boiler is just an old Thorn EMI backboiler, with a hot water cylinder, header tank in loft, 3-way Honeywell zone valve, Honeywell ST699 programmer, and the stat mentioned above. I have a feeling that something else is maybe wired up wrong in this old system, as mentioned when I had the original faulty wall stat the boiler was firing but the zone valve, pump were not running. Now with the new stat fitted the boiler is firing when told to by stat and the zone valve is opening, and pump running, but when the CM907 is not asking for heat (room temp below setpoint, flame icon off on the control display) the boiler is still firing at various intervals (with only heating set at On, on the programmer), but the zone valve and the pump are not starting. Unless it is the programmer as I have had trouble with these in the past, otherwise I have feeling that the system has maybe been wired incorrectly from day one. But then again I am obviously no expert. Any help please??
     
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  3. D_Hailsham

    D_Hailsham

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    According to diagram B? If the red wire is permanent live, it should go to the A terminal. B terminal is the switched live to the boiler.

    Is the red wire still being fed from the CH ON (terminal 3) of the old programmer? If so it would be better to connect it to a permanent live in the wiring centre and disconnect the wire between CH ON and the wiring centre at both ends. By doing this you completely bypass the old programmer for CH purposes; it is only used to control HW times.

    Here is the wiring diagram of a mid-position valve system. You will need to make the following changes for your system:
    1. No wire from Time controller CH ON to wiring strip terminal 4 (as suggested above)
    2. Room stat removed (leave wiring in place)
    3. Insert a wire linking T1 and T4 - this gives a permanent supply T4.
    4. Connect CM907 terminal A to T4 using the existing thermostat wire
    5. Connect CM907 terminal B to T5 using existing thermostat wire
    Everything else should be as the diagram

    [​IMG]
     
  4. smarty

    smarty

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    Cheers thanks very much for taking the time to reply. I am sure that you are correct I have wired the stat wrong, the wires need swapped around as the permanent live red wire is on Terminal 3 of the time/programmer. I am not that sure that I understand how to bypass the programmer though. Would this require running any additional wires as the wiring centre is upstairs etc. Sorry I am not an expert on this but I am learning. Thanks very much though it is very much appreciated :D
     
  5. D_Hailsham

    D_Hailsham

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    The only additional wire needed is a link between two terminals on the wiring centre.

    1. Disconnect the red permanent live from terminal 3 of the old programmer
    2. Disconnect the other end of the same red wire from the wiring centre.
    3. Make both ends of this wire safe (cut of the bare ends)
    4. Use a short length of wire (red if possible) to connect the same wiring centre terminal in step 2 to the Live input on the wiring centre (usually terminal 1).
     
  6. smarty

    smarty

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    Cheers mate thta is spot on, I will have to try that. I already tried swapping the red and yellow wires around on the CM907 to see if that is an easy fix but that solved nothing, still behaved the same which is odd. Will try the method you have suggested. Thanks very much for taking the time to reply :D
     
  7. smarty

    smarty

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    I spent a lot of time messing around with a multi-meter yesterday and this system has been very badly wired. The CH room stat is only switching the 3-way mid position valve, and the circulating pump. The programmer is starting the boiler, the only way round it is to turn the stat right up and just operate the heating via the programmer manually. The wiring in the wiring centre is nothing like the diagram above, the wiring centre also has no continous live it is controlled via the programmer. There is a seven pin terminal block and it is as follows.

    1) Switched live from CH Programmer Pin 3, to Red wire on CH heating room stat.

    2) All the neutrals go into this block from various things.

    3) All the earths go into here from various things.

    4) Yellow wire from Pin 8 on central heating programmer (com for DHW), connected to red wire going to live on the boiler, and brown wire going to hot water cylinder stat.

    5) & 6) used to connect various wires from the circulating pump, 3-way zone valve and hot water cylinder stat together.

    7) Switched yellow wire from CH room stat, this is only connected to the white wire that goes to the 3-way mid position valve. (which is in-turn connected to the circluating pump through terminals 5 & 6.

    The way I was looking at getting the CH heating room stat to control the heating and do away with the programmer was as follows.

    1) Connect the wire that was at pin 3 on CH heating programmer to the continous live on the CH heating programmer pin 1. This will go to terminal 1 in the wiring centre to the red wire in the wall stat.

    2) Connect the red live wire to the boiler that was in T4 on the wiring centre to T7, that is fed from the yellow wire from the room stat and is also connected to the zone valve and circulating pump.

    My only concern with this is that the hot water may not work correctly, as the yellow wire from T8 on CH heating programmer (com) is also connected to this, that also goes to the cylinder stats brown wire. Therefore there will be no connection to the boiler.

    Has anybody got any ideas about this. Thanks to D_Hailsham your advice is top notch. I am not an electrician but I am learning fast, and even I can tell that this system has been terribly wired :rolleyes: Other things that I noticed when checking for continuity of wires is that T5 & T6 on the central heating programmer go to the neutral terminal on the boiler.

    Thanks for any help.
     
  8. D_Hailsham

    D_Hailsham

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    That makes life awkward. ;) Is it possible to rewire so the main supply goes on to the terminal block an the programmer is then supplied from the block? You will need to replace the terminal block as you will need 8 terminals. You can buy wiring centres from DIY sheds for under a tenner. They usually have 10 terminals. You can then start again and wire up properly as per diagram and my previous instructions. I think that will be easier than trying to sort out the existing mess.

    The wiring of your ST699 should be as follows as follows:

    Make sure there is a link from L to pin 8 (may be via pin 5)
    Pin 7 is HW OFF and goes to terminal 7 in the diagram posted earlier
    Pin 6 is HW ON and goes to terminal 6 in the diagram.

    You only mention one wire from the HW stat (the brown going to terminal 4/7. There has to be three wires connected to this stat.

    I know it sound like a ling job, but it will be quicker - and easier to diagnose future problems.
     
  9. smarty

    smarty

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    Cheers mate I have looked in a little more depth, at what is going to T5 and T6 in the wiring centre. And you are correct the cylinder stat has 3 wires. This is the updated list.

    1) Switched live from CH Programmer Pin 3, to Red wire on CH heating room stat.

    2) All the neutrals (blue) go into this block from various things.

    3) All the earths (green/yellow) go into here from various things.

    4) Yellow wire from Pin 8 on central heating programmer (com for DHW), connected to red wire going to live on the boiler, and brown wire going to hot water cylinder stat.

    5) Live (brown) wire from circulating pump, Black wire from cylinder stat, orange wire to mid position 3-way valve.

    6) Grey from mid position 3-way valve, blue from cylinder stat.

    7) Switched yellow wire from CH room stat, this is only connected to the white wire that goes to the 3-way mid position valve. (which is in-turn connected to the circluating pump through terminals 5 & 6.

    Maybe I need to get the mulitmeter out again. Thanks very much though it is really appreciated as this is all pretty new to me :D

    Yes it is possible to run a live to the new terminal block and then supply the programmer with it by the way. I am willing to have a go at wiring this, but if I need to run new wires I may just live with the mess and it's shortcomings as I was planning on getting the boiler replaced next spring as I am fed up of it. Just has broken down several times, and the gas fire is hideous. But if it wasn't that difficult it would be worth altering the wiring to make it work correctly, as I actually enjoy learning how things like this work.
     
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  11. D_Hailsham

    D_Hailsham

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    That's a relief! At least something is right.

    As for you existing wiring shambles:

    1) Switched live from CH Programmer Pin 3, to Red wire on CH heating room stat.
    The terminal block needs a permanent live

    2) All the neutrals (blue) go into this block from various things.
    3) All the earths (green/yellow) go into here from various things.

    This is correct. All neutrals to one terminal and all earths to another

    4) Yellow wire from Pin 8 on central heating programmer (com for DHW), connected to red wire going to live on the boiler, and brown wire going to hot water cylinder stat.
    This is completely wrong. Whoever wired it up does not know what the pins on the ST699 do.

    5) Live (brown) wire from circulating pump, Black wire from cylinder stat, orange wire to mid position 3-way valve.
    I would expect the boiler to be connected here as well.

    6) Grey from mid position 3-way valve, blue from cylinder stat.
    There should also be another wire from the ST699

    7) Switched yellow wire from CH room stat, this is only connected to the white wire that goes to the 3-way mid position valve. (which is in-turn connected to the circluating pump through terminals 5 & 6.
    That's OK The CH stat switched live should connect to the MPV valve white.


    The only new wires will be the supply to the wiring centre; the rest is just reconnecting everything to the correct terminals (oh, and the link I mentioned earlier)
    Rewiring now will make life easier for the installer and probably cheaper for you.

    One last thing. Can you check that the mid position valve is the right way round. The port labelled A should go to the Central Heating; the Port labelled B should go to the HW cylinder.
     
  12. smarty

    smarty

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    Thats great advice mate. Thanks so much for the priceless advice. Regarding the valve I took the top off it as I know it had the position printed on there but that probably means nothing. Anyway hopefully they have got that correct. I took a photo of the valve as I was not totally sure, as it has AB stamped on the middle of the valve yet it has typed the other way on each port. Probably the one on each port so hopefully it is correct but I am no expert.

    [​IMG][/IMG]
     
  13. smarty

    smarty

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    Thanks mate I think you have explained it really well I know what to do. Just one last question, the ST699 currently has T3 & T7 linked, and it also has T5 & T6 linked. Should I just remove these now or leave these in place? Just wondered if both were needed with using the CM907 to control the heating, and the ST699 for DHW. Or maybe they need to be there if I wanted to use both at the same time, although this is not a necessity.
     
  14. D_Hailsham

    D_Hailsham

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    Yes, the valve is the correct way round. The port labelled AB is the entry port. the one stamped A is the CH and the one stamped B is the HW. When no power is applied to the valve, a spring loaded "stopper" blocks port A, so port B is open and water can enter at port AB and exit from port B. The motor can move the "stopper" to the middle, so water can exit from both A and B, or move the "stopper" right across so port B is blocked nad water then exits from port A. It's all explained in How a Mid position Valve Works

    No wonder you were having problems! Whoever wired up the system had absolutely no idea what they were doing. Remove both links. The only link you should have is between L and terminal 8.
     
  15. smarty

    smarty

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    Cheers again thanks very much for the advice. I have went over this and it all seems clear. Except T8 (com) on the ST699, does this just need a live linked to it and nothing else?
     
  16. D_Hailsham

    D_Hailsham

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    Yes T8 just needs a live link; it supplies power to the HW switch. When OFF T8 is connected to T7, when ON T8 is connected to T6

    Terminal 7 is HW OFF and goes to terminal 7 in the wiring centre
    Terminal 6 is HW ON and goes to terminal 6 in the wiring centre

    I suggest you print off my instructions and read them through - will make it clearer.
     
  17. smarty

    smarty

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    Will do cheers again :D
     
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