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Honeywell ST9400C programmer

Discussion in 'Plumbing and Central Heating' started by idiott, 4 Jul 2015.

  1. idiott

    idiott

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    Hello
    Can someone please help ?

    I mentioned a few days ago that I was having trouble with the thermostat re the hot water.

    Well I bought a new thermostat I switched off the power and dismantled the thermostat from the hot water cylinder. Well I discovered that the negative wire was loose. Anyhow I put the new thermostat in like for like.

    Now I have another problem! I switched the power back on. There is power in the system the boiler light is on the thermostat and the circuit breaker are all showing there is power.

    Here is the PROBLEM. My Honeywell programmer refuses to light up which means I cannot tell if it is working or not. I looked at the instructions on their manual it says move slider to run hold ok and minus buttons for 8 seconds. Well nothing happens

    Have I busted it. Help please
     
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  3. D_Hailsham

    D_Hailsham

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    As this is really a continuation of your problem with HW, it would have been better if you had added this to your post about the Honeywell cylinder stat.

    I assume that changing the cylinder stat did not solve the problem.

    I also assume that you just removed the programmer from the backplate at replaced it with the new programmer.

    Turn off the electricity, remove programmer and check that all the terminals on the back plate are done up tight.

    Do the same for all other cables, which probably go into a large junction box.

    As you have two motorized valves, there should be two wires connected to the cylinder stat.

    What do you mean by "the boiler light is on the thermostat"?
     
  4. idiott

    idiott

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    Thank you for replying It is appreciated.
    Sorry for confusing the issue. This exactly what happened and what I did.

    I assumed that my hot water cylinder thermostat was faulty as explained earlier. So I dismantled it only to discover that the negative wire was loose, the screw wasn't tightened as should have been during installation. Before embarking on this adventure I switched the power off by means of a power breaker so everything was dead including the ST9400C programmer.

    Fitted the new thermostat like for like turned the power breaker switch on all the lights on it are on showing its functioning. I lifted the boiler cover turned regulatory knob for the water to see if there was power there it lit up showing that there was power. I have a Vaillant boiler

    Now I went to check the programmer in fact to put in from auto to extra hour to test the thermostat only to discover that the programmer has stopped working it is blank no backlight.

    In short all I have done is turn the power off install new thermostat switch power on. I did not interfere with the programmer i.e. like dismantle it etc. The Honeywell booklet says. push the programmer slider to run press and hold ok and minus buttons well nothing happens.

    Is it busted if not I will appreciate it if someone could advise me how to get the programmer working
     
  5. D_Hailsham

    D_Hailsham

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    I don't know where I got the idea from that you also changed the programmer.

    It would still be a good idea to check all the terminals are done up tight. The Honeywell booklet will tell you how to remove the programmer from the backplate. Before replacing the programmer make sure the CH and HW switches are set to Off.

    Please report the result.
     
  6. D_Hailsham

    D_Hailsham

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    I should have asked how the cylinder stat is wired (colours/terminals).
     
  7. idiott

    idiott

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    Wiring on the terminals of stat brown on C and blue on 1 as per diagram and as was there before like for like
     
  8. idiott

    idiott

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    It seems I am getting nowhere fast so I am using the immersion heater for the time being. All I did was turn the power of change the cylinder thermostat (twenty minutes) Turn the power back on again and lo and behold the programmer stops working therefore paralysing the whole system.

    Maybe I should have done something very minor before switching the system off and on. Anyhow I have emailed Honeywell if anyone has the answer they would. The good thing about this programmer is that the circuits are pre wired and the programmer just clips on. So installing a new one is a ten minute job
     
  9. D_Hailsham

    D_Hailsham

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    Thanks for the info about cylinder stat wiring; I need to check that you hadn't accidentally connected the loose wire to earth.

    If the programmer is not lighting up, the first thing to check is that it is getting power. You have already found one loose wire, so there's a good chance there might be others. Which is why I have suggested, twice, that you check all connections are tight. You seem to have ignored this advice.

    Honeywell don't have a crystal ball.

    The only advice they will give you is to employ a qualified engineer and possibly provide you with the name of a Honeywell approved installer.
     
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  11. idiott

    idiott

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    Thank you for your reply sorry for all the trouble I am causing.

    Yes I have checked the power supply

    1 Power breaker switch Orange light on

    2 Below the Breaker junction box all wires firm and screwdriver tester showing positive (red) power supply

    3 Programmer, I unhinged it from circuit panel, tested the incoming wiring on the panel with screwdriver tester, it showed positive (red) power supply. However the front (programming face) there is no power to light it up just blank screen like the old TV green screen

    I tightened all connections where possible



    Tightened all wire connections
     
  12. D_Hailsham

    D_Hailsham

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    Screwdriver testers are not always reliable; a multimeter is better.

    It does look as if the programmer has given up, but changing the cylinder stat should not have caused this.

    Did you follow my suggestion to turn CH and HW Off before refitting the programmer? If so, did this make any difference?
     
  13. idiott

    idiott

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    Thank you I did not need to turn the CH & WH off because before I changed the thermostat I had done that. Anyway all the instructions on the programmer have been on a blank green screen from the time I put the new thermostat in and put the power on. so nothing can be read
     
  14. Boilerman2

    Boilerman2

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    It is not un-common for a Honeywell Programmer to fail in this way - even mine at home did this when I had to do some work elsewhere that involved switching the power off - new programmer should sort it!
     
  15. idiott

    idiott

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    Thank you Boilerman2
    I had a similar problem but that was back in 1984 when Honeywell LED programmers first came out so I went back to the mechanical clock type. I thought they would have corrected this issue.

    However, I grateful for your advice. So I have ordered a replacement. Can you please tell me the steps I should take installing the replacement. i.e.

    1 I should shut the power down obviously
    2 Should the room thermostat (mine wireless) be set to high or low
    3 CH & HW on programmer will only appear on the screen once power is switched on
     
  16. Boilerman2

    Boilerman2

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    1. YES
    2. Doesn't Matter
    3. Correct
     
  17. idiott

    idiott

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    REPORTING BACK

    Thank you for helping me with the problems I was having with my programmer (Honeywell ST9400C).
    As reported earlier I purchased a new programmer it arrived 2 hours ago. I installed it. Switched the power on the system is running beautifully, back to normal.

    However, I am disappointed with Honeywell who are a well established company of over a hundred years. They could or should built in a cut out system that would shut the programmer down on a surge to the system. Mind you I told them so and asked them for advice on installing the new programmer. Well they only game advise on installations. No other comment.

    Anyway thanks everyone
     
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