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Thread: Hot Water issue - Random Overshoots

  1. #21
    Automated Home Legend paulockenden's Avatar
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    If there was a design flaw in the CS92 (or firmware) surely we'd all be seeing these comms errors with our DHW? I'm with the poster above - I suspect you have a faulty CS92.

  2. #22
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    Quote Originally Posted by mtmcgavock View Post
    Is it not possible that your CS92A is faulty?

    After the one I have replaced the issue doesn't seem to have reoccurred, although I did carry out the various steps you mentioned on the new device to ensure there was no issue. And I am right in thinking yours is still in the same room as the BDR91's? How far away is it from the main panel.
    Yes the CS92A is in the closet with the boiler and the hot water cylinder. (Although it's only a small 100 litre cylinder) It is 70cm from the nearest BDR91 and 50cm from the cylinder. Distance to the controller which is permanently wall mounted is 6 metres with line of sight through the closet wall and a glass door. Signal test is 5/5.

    I've already moved the CS92A as far away from other objects as possible - moving it further away from the BDR91's last year did help quite a bit but it is still not completely reliable.


    Quote Originally Posted by paulockenden View Post
    If there was a design flaw in the CS92 (or firmware) surely we'd all be seeing these comms errors with our DHW? I'm with the poster above - I suspect you have a faulty CS92.
    Perhaps, but only if it is faulty from new. You only have to look on forums to see how common these symptoms are though. I had a look on the evohomeshops own forum a couple of days ago and found 3 threads in the last few months all for the same problem I'm seeing of intermittent hot water overshoots. So I doubt it is an isolated experience given the relatively few threads on that forum in total.

    The level of troubleshooting that I've already performed in the last 9 months is already well beyond what would be expected from a normal end user so I think I'll email Richard and ask him if he will swap it. (I think it's still within the warranty) I'm sceptical that it will help though. I think the problem really is just a result of the less than 100% reliable communications protocol in anything other than perfect and unrealistic RF conditions.
    Last edited by DBMandrake; 18th July 2017 at 12:14 PM.

  3. #23
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    Do you not think it is possible that there is interference from the Relays? Then again the HW kit at my parents is probably more than 70cm closer and we don't appear to have any issue there. Have you also checked your probe connections as I suppose if you don't have a good connection then it wouldn't read the temperature.

    The most obvious thing seems to be that your CS92 is faulty, bar the one that I had the issue with i've had little issue with the ones i've installed so far. Now when all the batteries start going that might be another issue.

  4. #24
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    Richard sent me a replacement CS92A which I installed on Sunday.

    It has gone back into the same location with the same original batteries (still 1.57v) and I deliberately did not bend any battery contacts etc. I also swapped the strap on sensor to be thorough, although I don't think it could be related to the problem I was seeing. All bindings were thoroughly cleared and I set up the whole stored hot water section from scratch. (EG cleared and rebound all BDR91's etc)

    So far, touch wood, I have not noticed any overshoots, but it has only been a few days. Based on the unpredictable and intermittent nature of the problem it will need to run without problems for a couple of months before I can draw any real conclusions. Fingers crossed!

    The part number of the replacement is identical to the original - only the date code differs, but I suppose its theoretically possible that the newer unit could have revised firmware on it that would alter its sampling and transmission behaviour.
    Last edited by DBMandrake; 2nd August 2017 at 11:16 AM.

  5. #25
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    Two weeks since swapping the CS92A without an overshoot. Promising so far but still too soon to draw any firm conclusion.

    I'm crossing my fingers that the problem is properly resolved though..!

  6. #26
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    Quote Originally Posted by DBMandrake View Post
    Two weeks since swapping the CS92A without an overshoot. Promising so far but still too soon to draw any firm conclusion.

    I'm crossing my fingers that the problem is properly resolved though..!
    The CS92A I replaced that was showing the same issues has also been fine over a 4 week period. Could it have been they were both faulty units?

  7. #27
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    Just a thought.....could it be that it is summer time? I too have found my CS92 to be behaving well in recent weeks. In earlier months, the DHW heating would often trip out on the mechanical thermostat in my cylinder and the CS92 would only catch up some minutes later to show that the temperature had gone well past the setpoint. That has not happened recently. Could it be that there is much less RF chatter going on while we have our heating off and the DHW is the only heating demand?

  8. #28
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    Nearly a month and no overshoots that I'm aware of, although I haven't scrutinised my Domoticz logs to be 100% sure.

    So it looks like I had a faulty unit. I'm not sure if that's good or bad to be honest! Good that it may not have been a fundamental comms design flaw as I was beginning to suspect, but bad in that it was faulty from new, and I'm not the only one to run into this problem.

    Right back from new it was giving trouble although most of the symptoms went away after tensioning the battery contacts on the rear of the PCB - as it did for some other people with similar problems. But it never really fixed it 100% it seems, it just put it into remission.

    Perhaps its something like the copper trace on the rear of the PCB being slightly oxidised from new, never quite getting a reliable connection. The spring contacts aren't a particularly good spring steel so seem to lose their tension over time, which wouldn't have helped if there was some oxidation. (Same problem with poor spring steel in the battery contacts in the HR92, which I've had to re-tension on 3 HR92's now)

    I'm happy at least that it seems to be functioning normally now, whatever the underlying reason.
    Last edited by DBMandrake; 29th August 2017 at 09:03 AM.

  9. #29
    Site Sponsor The EVOHOME Shop's Avatar
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    Good news, glad its been resolved...

  10. #30
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    Quote Originally Posted by The EVOHOME Shop View Post
    Good news, glad its been resolved...
    I would not want you to remove this from your list of 'issues' for the Evohome kit. I am still wary of my CS92 and regard it as a dodgy bit of kit. True, it seems to be working OK during the summer but let's see what happens when I put my heating back on again and there is a lot of RF traffic going to and from my boiler room.

    I suspect that it is only the 'nerds on this forum' who are spotting overshoots on their CS92s. Those on the forum who are principally installers may cite no known problems. But that is probably because 'normal' users would not be aware of an overshoot by the CS92 and thus not report anything to their installer. Especially if, like mine, the DHW valve control is wired in series with a mechanical thermostat in an unvented cylinder, the user will not know (or care) whether the hot water heating is terminated by the CS92 reaching the set point or by the mechanical thermostat operating. Unlike we nerds, most users will not obsess over the controller to see the DHW temperature, so they will simply know that they have hot water when they expect it and will not identify any problem.

    That could imply that, if a normal user would not see a problem, it is not a problem worth fixing. But I am still uneasy about the robustness of the CS92 control of my DHW heating and I would be very nervous if I did not have the mechanical thermostat as backup.

    Please do not close your file on the CS92 overshoots just yet.

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