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Thread: How best to sense a fault in hot water

  1. #1
    Automated Home Sr Member Alexc's Avatar
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    Default How best to sense a fault in hot water

    I have expanded my Idratek network sufficiently that I can now move to controlling the heating and hot water system. I will be trying this over the next few days, using a QRH Din module with a changeover relay for the HW and NC relay for the heating.

    I had a boiler failure a few months ago (only needed resetting, but meant no hot water in the morning!) and needed to use the immersion heater. Therefore, incorporated into this new setup is my immersion heater on a relay contact. I've written this up here.

    Here's my plan - will it work?

    My heating system is Y-plan (3-port valve). When the boiler/pump are on, the orange wire from the valve is live (240v). Therefore if Cortex expects the water to be heating up (eg 5.30am) then there will be 240v at this terminal.

    If I run a neon indicator from this terminal (and neutral) and then use a BPW85C opto transistor (Farnell ref: 1045524) (as in a previous post regarding electricity meters) to sense whether the neon is on, and feed this into the input of the QRH, will this work and be sensible?

    I have put a pipe thermostat on the flow pipe to the HW cylinder, and this also goes into one of the inputs. Therefore, if it's between 5.40am and 6.00am and the opto transistor detects light, then the pipe thermostat should be hot. If it is not, then Cortex should switch on the immersion heater and generate a warning for checking later.

    Logically this will work, but of course there could be other failures. If the motorised valve fails, there might be no current on the orange wire, and therefore still no hot water! So I wonder if I should be using two neons and opto transistors, on both the grey and orange wires. Here's why:

    Grey would be live if it is not calling for heat or if the temperature had already been reached. Therefore:
    If HW on (Cortex) and Grey live, then temp reached and no trigger (END)
    If not above, then If HW on (Cortex) and Orange live, check for pipe hot. If not hot, turn on immersion heater and warn.

    Any thoughts?

    Alex.

  2. #2
    Automated Home Legend chris_j_hunter's Avatar
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    some thoughts ...

    sounds a complicated way to do it ...

    Cortex includes objects to manage heating etc - HVAC, ThermalStore, etc ... Relay options include valves etc ... there are also things like the Verifier ... and Thresholds in various sensor objects, too ...
    Last edited by chris_j_hunter; 4th August 2015 at 12:46 PM.

  3. #3
    Automated Home Sr Member Alexc's Avatar
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    Thanks Chris. I hadn't come across 'verification logic' before, so will have a go with that. Still waiting for my Cortex to update!

  4. #4
    Automated Home Ninja Viv's Avatar
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    [QUOTE= Still waiting for my Cortex to update![/QUOTE]

    A number of users have reported their Cortex has not updated to version 27.
    Clearing the Internet cache seems to help

    Viv

  5. #5
    Automated Home Legend chris_j_hunter's Avatar
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    we've searched our PC for cache files, and found quite a few, but not any that look likely ... so, any clues would be welcome !
    Last edited by chris_j_hunter; 5th August 2015 at 05:50 PM.

  6. #6
    Automated Home Sr Member Alexc's Avatar
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    I had already tried flushing the DNS cache, which didn't work. I cleared the cache in Internet Explorer, and it has now upgraded to v27. Thanks.
    I was reading the change log, but it disappeared after a while. The help file is still v26 - is there a change log I can see anywhere?

  7. #7
    Automated Home Legend Karam's Avatar
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    You can find the Update History files by visiting the Auto update menu and click on the top right wording 'Update History'.

    Regarding the Hot water, is there a need to sense the orange wire state? I.e if the grey wire tells you whether temperature has already been reached and Cortex knows when HW is to be ON, then isn't it sufficient to measure the flow temperature when HW is ON and grey wire indicates that boiler is being demanded, or alternatively to measure the thermostat state instead of grey wire for proxy of boiler demand when HW on.?

  8. #8
    Automated Home Sr Member Alexc's Avatar
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    Thanks Karam. Yes, that makes more sense as the orange would be live on heating demand too. I will have a go with that.

    Thanks for pointing me to the update info too.

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