Page 2 of 5 FirstFirst 12345 LastLast
Results 11 to 20 of 42

Thread: Hot Water issue - Random Overshoots

  1. #11
    Automated Home Legend
    Join Date
    Sep 2014
    Location
    Scotland
    Posts
    1,804

    Default

    My HR92 batteries (original factory supplied Alkaline) are lasting on average 18 months. I've just replaced the hallway and kitchen ones recently when they were generating multiple warnings in the fault logbook. In fact the hallway one went flat enough that the HR92 "crashed" with all symbols lit up on the screen at once and it was non-responsive.

    The batteries in my CS92A were fine (1.5v is perfectly normal for Alkaline) and had only been in since October 2016, but it had started to give issues with overshoots and the occasional middle of the night comms fault from the sensor.

    The battery drain of the CS92A should be very low - much lower than an HR92, however it (at least mine) seems to be a lot more sensitive to low voltage than an HR92, which will usually keep working until the battery can't turn the motor anymore...

  2. #12
    Automated Home Sr Member
    Join Date
    Jan 2016
    Location
    Harrogate, North Yorks
    Posts
    93

    Default

    Thank you for your inputs. It looks like my average for HR92 is also around 18 months but CS92A looks as if it's going to be 2 years.

    On some of my bedroom HR92s, I have had controller warnings about the battery (whilst still showing 2 bars on HR92 display) and then they carry on working, albeit with intermittent battery warnings often in the small hours when heating off, until eventually the battery dies sometimes up to two months after warning of its imminent demise! Go figure that one?

  3. #13
    Automated Home Ninja
    Join Date
    Mar 2017
    Posts
    293

    Default

    Quote Originally Posted by DBMandrake View Post
    Yes, I had this problem a lot when I initially installed my hot water kit. I had my hot water set to 50 at the time (I now use 54) and it was overshooting to 62 degrees on a fairly regular basis - about 5 to 10 times a week. Always to 62 degrees.

    I've discussed this problem at length and its (mostly) solution in these two threads and possibly in other threads, so you might want to skim read them both:

    http://www.automatedhome.co.uk/vbull...vershoot+water

    http://www.automatedhome.co.uk/vbull...vershoot+water

    I'll give you a quick summary before you read those for more detail. In my case there were two issues.

    1) The CS92A seems to be very sensitive to low battery voltage, and starts reporting in very infrequently or not at all if there is any problem with the battery voltage or battery contacts. This leads to hot water overshoots as the sensor doesn't report that the set temperature has been passed in a timely fashion.

    I've heard from a source that should know that it's a relatively common problem that the battery contact tension behind the PCB is inadequate from the factory on some units - the solution is to carefully remove the PCB board from the casing, (just push back a couple of plastic tabs at the top then carefully tilt it out) and gently bend up both the battery interconnects that press up on the underneath of the board about 2-3mm to increase their tension, then re-install the board. In my case this solved about 90% of the overshoots right away.

    I haven't tried it yet but I suspect that running the CS92A on Lithium batteries instead of the supplied Alkaline batteries may also help, because lithium batteries have both a higher initial terminal voltage than Alkaline (about 0.1 - 0.2 volts higher) and more importantly the voltage stays nearly the same until the cell is nearly exhausted before dropping, compared to Alkaline where there is a steady decline in voltage as the cell is depleted.

    Just in the last few weeks (after over 6 months of no trouble) I've started to have a few overshoots again and I took the batteries out (factory original Alkaline) and they measured exactly 1.5v - which should be fine for Alkaline, however I swapped them for some new Alkaline's of a different brand which measured 1.6v and the problem went away immediately and hasn't returned, which tends to confirm my voltage sensitivity theory. I would have tried some Lithium's but I didn't have any on hand at the time, but I think I will get some to give them a try.

    2) Changing the hot water set point, especially increasing it can lead to overshoots because the set point is "missed". Hard to explain why without going into a lot of technical detail - check those two threads for the explanation. The workaround is a few minutes after changing the hot water set point or differential, reboot both the controller and the CS92A (by unplugging the controller and removing its batteries temporarily, and removing the batteries of the CS92A temporarily) and this will fix this problem.

    3) Minor comms problems from the CS92A to the controller can cause some temperature update messages to get lost. The symptoms are less frequent temperature reading updates when the cylinder is heating and occasional overshoots. I spent a lot of time on this problem and it turned out to be the location of the CS92A. The CS92A and my 3x BDR91's are in the boiler closet and were previously mounted on the same wall in the same orientation stacked vertically with about 300mm between each one, which should be fine according to Honeywell's specs. The signal test from the CS92A was also always 5/5.

    Unfortunately I've found the signal test fairly useless at troubleshooting comms issues, as a good signal doesn't guarantee trouble free comms, nor does a lesser signal (like 3/5 or 4/5) indicate problems! What I ended up doing was moving the CS92A to a wall of its own (at 90 degrees to the original wall) in the boiler closet a bit further away from the BDR91's and at a 90 degree orientation to what it was before. Signal test now reports 3/5 or 4/5 and line of sight to the controller is not as good as before (it's now going through two walls instead of one to exit the closet) but despite this the overshoots went away. So it seems that the CS92A doesn't like to be too close to BDR91's, and the 90 degree orientation between them probably helped. (Depending on how the antennas are orientated inside the casing of the devices, a 90 degree orientation difference would cut any interference between the two down dramatically)

    BTW 62 degrees seems to be a safety trigger temperature for the CS92A sensor - it uses a battery saving algorithm to only send temperature updates when the temperature is either changing rapidly, or changing within the differential range or crossing the set point, however it also seems to always send updates when it reaches 62 degrees regardless of what the set point is, hence why in my case with my 50 degree set point it was always overshooting to exactly 62 degrees on the occasions that it did overshoot.


    To delete the hot water kit you would unbind the BDR91's (15+ second press on the relays until they flash fast) and set stored hot water to none. Then you can bind the new ones. You'll lose your hot water schedule and set point but your heating zones will be unaffected. So take a note of the hot water schedule and hot water settings first.
    Thanks for the information, it has been very useful. Out of the 5 hot water kits I have installed this is the first to show any issues, however most are only now 12 months old.

    As the new CS92A receiver had come I decided to put it in anyway but I took the circuit board out bent over the contacts more and did this on the battery - funnily enough I had the exact same problem on a DT90E a couple of month ago where the contacts weren't even touching from factory.

    I tested the batteries that came with it - they were reading 1.61v so i've gone with them. (The ones in the old receiver were 1.6v) I usually upgrade everything to Lithium when doing an install but my local supplier keeps failing to keep AAs in stock. In future I think I may only use these.

    Yes I would agree the 62oc seems to be some sort of fail safe as it seemed to reach this temperature every time, however i'm not sure what would happen if you have your HW set greater than 62oc?

    So once everything was up and running it heated up fine and the controller seemed to update on a regular basis the temperature increase and then shut off at the set point. Obviously only time will tell now as this only appeared to happen once a week. However going to my own EvoHome I find that it takes a while to update the temperature on the panel when heating (Longer than the system this morning). In the past I thought it was just a flaw in the design of the EvoHome but I might investigate that a bit further. There has only been a couple of times when we've run out of hot water - I just put the down to the 50oc set point with a 10oc drop, coupled with the fact my heat exchanger is cast iron so takes longer to heat up from cold. However it could be possibly be the EvoHome not updating quick enough.

  4. #14
    Automated Home Legend
    Join Date
    May 2014
    Posts
    988

    Default

    Quote Originally Posted by mtmcgavock View Post
    Thanks for the information, it has been very useful. Out of the 5 hot water kits I have installed this is the first to show any issues, however most are only now 12 months old.

    As the new CS92A receiver had come I decided to put it in anyway but I took the circuit board out bent over the contacts more and did this on the battery - funnily enough I had the exact same problem on a DT90E a couple of month ago where the contacts weren't even touching from factory.

    I tested the batteries that came with it - they were reading 1.61v so i've gone with them. (The ones in the old receiver were 1.6v) I usually upgrade everything to Lithium when doing an install but my local supplier keeps failing to keep AAs in stock. In future I think I may only use these.

    Yes I would agree the 62oc seems to be some sort of fail safe as it seemed to reach this temperature every time, however i'm not sure what would happen if you have your HW set greater than 62oc?

    So once everything was up and running it heated up fine and the controller seemed to update on a regular basis the temperature increase and then shut off at the set point. Obviously only time will tell now as this only appeared to happen once a week. However going to my own EvoHome I find that it takes a while to update the temperature on the panel when heating (Longer than the system this morning). In the past I thought it was just a flaw in the design of the EvoHome but I might investigate that a bit further. There has only been a couple of times when we've run out of hot water - I just put the down to the 50oc set point with a 10oc drop, coupled with the fact my heat exchanger is cast iron so takes longer to heat up from cold. However it could be possibly be the EvoHome not updating quick enough.
    It is worth pointing out that with an unvented cylinder the Evohome HW kit should always be installed in series with the HW target temperature with a setting below that of the cylinder's own unvented stat. It follows that a failure of the CS92A should not result in anything too frightening/dangerous. Keeping HW in the range 50 to 40C may be asking for problems. I have a 250L cylinder which heats up to 60C +/- 5C. The average daily cost for the past 7 days has been 30p which includes a 12.6p standing charge. I am not sure that I would save much by dropping the cylinder temperature to 50C.

  5. #15
    Automated Home Ninja
    Join Date
    Mar 2017
    Posts
    293

    Default

    Quote Originally Posted by HenGus View Post
    It is worth pointing out that with an unvented cylinder the Evohome HW kit should always be installed in series with the HW target temperature with a setting below that of the cylinder's own unvented stat. It follows that a failure of the CS92A should not result in anything too frightening/dangerous. Keeping HW in the range 50 to 40C may be asking for problems. I have a 250L cylinder which heats up to 60C +/- 5C. The average daily cost for the past 7 days has been 30p which includes a 12.6p standing charge. I am not sure that I would save much by dropping the cylinder temperature to 50C.
    Yes the cylinder stat should always be wired in due to fail safe of the cylinder stat and the high limit stat on the cylinder - it's part of the regulations. Also they should be on a 2 port valve - the many jobs I go to and someone has installed a unvented cylinder on a 3 port valve is frightening.

    I have mine set at 50oc purely because anything higher I find my hot taps too hot - I suspect you are right that you don't spend much more in terms of cost. However it's amazing how much longer it takes to heat that extra 15oc. You would have to test it and work out the difference.

  6. #16
    Automated Home Sr Member
    Join Date
    Sep 2015
    Posts
    59

    Default

    Quote Originally Posted by DBMandrake View Post
    My HR92 batteries (original factory supplied Alkaline) are lasting on average 18 months. I've just replaced the hallway and kitchen ones recently when they were generating multiple warnings in the fault logbook. In fact the hallway one went flat enough that the HR92 "crashed" with all symbols lit up on the screen at once and it was non-responsive.
    I've had similar with one of my HR92's which is in the conservatory, it literally complained once on the controller about low battery the same morning, but when the HR92 was touched, or the dial rotated, it would crash, show all the symbols on the LCD & restart itself.

  7. #17
    Automated Home Legend
    Join Date
    Sep 2014
    Location
    Scotland
    Posts
    1,804

    Default

    Quote Originally Posted by mtmcgavock View Post
    Thanks for the information, it has been very useful. Out of the 5 hot water kits I have installed this is the first to show any issues, however most are only now 12 months old.

    As the new CS92A receiver had come I decided to put it in anyway but I took the circuit board out bent over the contacts more and did this on the battery - funnily enough I had the exact same problem on a DT90E a couple of month ago where the contacts weren't even touching from factory.
    I've also had this problem with the battery contacts in the bottom of a couple of HR92's - the grade of steel used for the contacts does not seem to be "proper" spring steel as spiral shared battery contacts usually are so it loses its tension relatively easily.
    I tested the batteries that came with it - they were reading 1.61v so i've gone with them. (The ones in the old receiver were 1.6v) I usually upgrade everything to Lithium when doing an install but my local supplier keeps failing to keep AAs in stock. In future I think I may only use these.
    1.6v should be plenty. The main advantage of the Lithium's is they won't drop below 1.6v until the battery is nearly depleted whereas an Alkaline will be down to more like 1.2v by then.
    Yes I would agree the 62oc seems to be some sort of fail safe as it seemed to reach this temperature every time, however i'm not sure what would happen if you have your HW set greater than 62oc?
    I don't know what would happen either - but all my overshoots when the battery contact issue was there were to exactly 62 degrees, regardless of whether my HW was set to 50 or 55 degrees, so there is something special about 62.
    So once everything was up and running it heated up fine and the controller seemed to update on a regular basis the temperature increase and then shut off at the set point. Obviously only time will tell now as this only appeared to happen once a week. However going to my own EvoHome I find that it takes a while to update the temperature on the panel when heating (Longer than the system this morning). In the past I thought it was just a flaw in the design of the EvoHome but I might investigate that a bit further.
    It seems to be normal for it to update infrequently when it is below the differential range. So for example if you had 55 as the set point and 10 as the differential, below 45 degrees it only updates after the temperature has changed many (5-10) degrees so the nothing will appear to be happening for a long time during initial heating, but then when it reaches 45 it will start updating much more frequently - usually every 1 or 2 degrees, and also when it hits the set point - 55 in this case.

    Unfortunately it seems to go back to infrequent updates again once the temperature has gone past the set point on the assumption that the system will stop heating. But if that message doesn't get through for some reason it results in an overshoot, and another update isn't sent until 62 degrees.

    There has only been a couple of times when we've run out of hot water - I just put the down to the 50oc set point with a 10oc drop, coupled with the fact my heat exchanger is cast iron so takes longer to heat up from cold. However it could be possibly be the EvoHome not updating quick enough.
    I'm very familiar with how much I can run the hot tap before it starts dropping low enough to trigger a reheat, and I had run it much longer than I would have expected, and it still said 52 degrees (with a 54 degree set point and 5 degree differential) so I started to get suspicious.

    I turned the tap off and left it for 5 minutes and it still claimed 52 degrees but I knew it couldn't be. I removed the battery from the CS92A and reinserted it and the reading immediately jumped to about 30 degrees. This is exactly the sort of symptom I used to see back when I had the original battery contact problems - long periods of time with no change in the reading and yet the correct reading was always sent when the batteries were reconnected. That's when I decided to change the batteries again.
    Last edited by DBMandrake; 30th June 2017 at 12:30 PM.

  8. #18
    Automated Home Legend
    Join Date
    Sep 2014
    Location
    Scotland
    Posts
    1,804

    Default

    And again today, a "Comms error" with the hot water sensor reported on the touch panel, and an hour glass reported instead of the temperature. Hot water was scheduled on and up to temperature at the time.

    I pressed the signal test button on the CS92A and it immediately reported 5 flashes for a full 5/5 signal. I then removed the battery and refitted it and the controller immediately reported the temperature and cleared the "comms fault".

    When you consider that the hot water sensor sends an update at least once an hour, and has to fail to report in for about 3 hours before a hot water sensor fault is logged on the controller, I can't see any way that this is a real comms fault, especially given that it immediately reported a 5/5 signal, and re-inserting the batteries immediately sent through a temperature reading. (These are new batteries too, fitted 2 weeks ago)

    I wonder when Honeywell will admit that there a design flaw in either the hardware of the CS92A or a bug in its firmware where it just fails to send temperature updates for long periods of time ? Random inexplicable "loss of communication" and the occasional hot water overshoot despite doing a large amount of troubleshooting and investigation into the problem is getting very tiresome indeed. Something as simple as a temperature sensor for a hot water cylinder should just work, and work reliably.

    Looks like I might have to get an HGI80 to prove once and for all where the real problem lies...
    Last edited by DBMandrake; 15th July 2017 at 04:04 PM.

  9. #19
    Automated Home Guru
    Join Date
    Dec 2016
    Posts
    123

    Default

    Quote Originally Posted by DBMandrake View Post

    I wonder when Honeywell will admit that there a design flaw in either the hardware of the CS92A or a bug in its firmware where it just fails to send temperature updates for long periods of time ? Random inexplicable "loss of communication" and the occasional hot water overshoot despite doing a large amount of troubleshooting and investigation into the problem is getting very tiresome indeed. Something as simple as a temperature sensor for a hot water cylinder should just work, and work reliably.
    All of which supports the plea for Honeywell, in its next evolution of this product, to provide a mains-powered CS92 replacement. This would ideally fit into an identical baseplate to a BDR91 to ease the wiring and appearance when mounted in an array of BDR91s. The cylinder probe cable can be extended quite significantly with no material degradation in the accuracy of the temperature sensing so the location of the CS92 is not really a constraint and should be as easy to power from the mains as any BDR91. That should enable Honeywell to redesign the software to give much more frequent and reliable temperature updates without worrying about battery life.

  10. #20
    Automated Home Ninja
    Join Date
    Mar 2017
    Posts
    293

    Default

    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.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •