Results 1 to 10 of 18

Thread: Evohome DHW overshoots

Threaded View

Previous Post Previous Post   Next Post Next Post
  1. #8
    Automated Home Legend
    Join Date
    Sep 2014
    Location
    Scotland
    Posts
    1,894

    Default

    Any luck ? I had my first hot water overshoot in months this morning, here is the CSV output from Domoticz. Keep in mind I use the Web API scripts which means I only get readings every 5 minutes, not at the times when readings are transmitted. Hot water set point is 54 degrees with a 5 degree differential. Notice how the reading rose to 52.56 then "stuck" there for a full 65 minutes before the reading suddenly jumped to 64.75. In reality the temperature would have been rising that whole time, but no updates were being sent. (or received - hard to be sure which)

    Code:
    20/02/2017 04:50	0	20/02/2017 04:50	43.11
    20/02/2017 04:55	0	20/02/2017 04:55	43.11
    20/02/2017 05:00	0	20/02/2017 05:00	43.11
    20/02/2017 05:05	60	20/02/2017 05:05	43.33
    20/02/2017 05:10	60	20/02/2017 05:10	43.33
    20/02/2017 05:15	60	20/02/2017 05:15	50.07
    20/02/2017 05:20	60	20/02/2017 05:20	52.56
    20/02/2017 05:25	60	20/02/2017 05:25	52.56
    20/02/2017 05:30	60	20/02/2017 05:30	52.56
    20/02/2017 05:35	60	20/02/2017 05:35	52.56
    20/02/2017 05:40	60	20/02/2017 05:40	52.56
    20/02/2017 05:45	60	20/02/2017 05:45	52.56
    20/02/2017 05:50	60	20/02/2017 05:50	52.56
    20/02/2017 05:55	60	20/02/2017 05:55	52.56
    20/02/2017 06:00	60	20/02/2017 06:00	52.56
    20/02/2017 06:05	60	20/02/2017 06:05	52.56
    20/02/2017 06:10	60	20/02/2017 06:10	52.56
    20/02/2017 06:15	60	20/02/2017 06:15	52.56
    20/02/2017 06:20	60	20/02/2017 06:20	52.56
    20/02/2017 06:25	60	20/02/2017 06:25	52.56
    20/02/2017 06:30	60	20/02/2017 06:30	64.75
    20/02/2017 06:35	60	20/02/2017 06:35	64.75
    20/02/2017 06:40	60	20/02/2017 06:40	64.75
    As my boiler flow temperature is only set to 70 at the moment 65 degrees is about the hottest the hot water will get even if the hot water zone valve remained open permanently. Good thing my boiler doesn't use an 80 or 90 degree flow temperature boost for hot water or my hot water would have been REALLY (dangerous, scalding) hot this morning after a 65 minute overrun!

    No idea what caused it - no fault logbook entries and no other signs of system misbehaviour, and the hot water behaviour has been flawless for months.

    One question - do you have Alkaline batteries in your CS92A or have you put lithiums in ? I'm considering putting Lithiums in mine because they hold their terminal voltage higher for a lot longer as the battery discharges, and the device does seem to be sensitive to low battery voltage either due to low batteries, or poor battery contact. So a battery that keeps a higher terminal voltage for a longer portion of its life may be beneficial. So far I have only ever used Alkaline's in all my Evohome devices for cost reasons, but I'm starting to reconsider that due to the superior voltage discharge curve of lithium batteries.
    Last edited by DBMandrake; 20th February 2017 at 10:37 AM.

Posting Permissions

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