Cancelling "Presence Override"

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  • jpdw
    Automated Home Guru
    • Oct 2007
    • 169

    Cancelling "Presence Override"

    Hi.. Quick question ...

    I've got 1 HVAC floor that doesn't have presence sensors. It's a guest room & study/office, so I've got the unoccupied setpoint nice and low for when it not used, the occupied reasonable for when it is.

    I've got a DRB button connected to the floor's "Override" connection.
    This seems to allow me to toggle the "Presence Override" setting on the HVAC object, so I press the button when the floor is going to be used (usually me working at home) then press again to cancel @ end of the day.
    ... this works well ...

    But sometimes I forget to press @ end of the day, so the presence override stays on and this can sometimes go through the night -- which is unnecessary heating.

    I want to put something in the scheduler to cancel the Presence Override at, say, midnight each night (obviously if we have guests staying, I'll disable this). But the Override seems to be a toggle not an Enable/Disable.

    Is there a Presence Override Enable/Disable input ? Or even if there was an output reflecting the state of Presence Override, then some logic could be used to determine whether to toggle or skip.

    Thanks,
    Jon
  • Viv
    Automated Home Ninja
    • Dec 2004
    • 284

    #2
    The Floor object does not have an override input.
    The HVAC object does have an override input.
    This overrides the presence state for the HVAC. In effect keeping the presence condition even if the room is not occupied and so to ensure it reaches the occupied profile.

    Its purpose is to allow the HVAC to get the room up to occupied temperature even when nobody is present. However this presence override state is removed when the temperature exceeds the set-point.

    For your circumstances you might be better with a different setup...

    You could set the All HVAC object Fall back temeprature to a suitable low level say 18C. You set your HVAC unoccupied profile to some desired profile for when you are using the rooms e.g. 21C. You can then toggle the fallback option of the HVAC to switch between these two levels. The Fallback option would be turned on (Fall back enabled) when the room is not used and turned off (Fall back disable) when the room is occupied.

    The fall back state can be set by the scheduler to ensure it is set to the required state should you forget.

    This method obviously means you have a fixed level (fall back temperature) when the room is not in use but a profiled temprature when it is in use.

    A rather more elaborate way is to have two HVAC controllers and switch between the two, setting the operation mode as required.

    Viv.

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    • jpdw
      Automated Home Guru
      • Oct 2007
      • 169

      #3
      Thanks Viv. I'll give that a go when I get home later in the week.

      Apologies if I put 'floor' I meant HVAC object - which I've got associated with an entire floor - but I think you guessed that bit.
      Jon

      Comment

      • jpdw
        Automated Home Guru
        • Oct 2007
        • 169

        #4
        Re-heating (!) an old thread, but I never quite sorted this out earlier in the year then it got warmer and issues around heating became less a concern. Now we're back to winter.....

        As I understood the suggestion, I'd be using the 'whole house' fallback rather than just fallback for a single zone. However, I'm already using this feature for setting a holiday/away mode - ie prolonged temperatures lower than the normal occupied/unoccupied settings. And I'm already using 3 HVAC zones (1 per floor) but ultimately want to subzone further (per room in some cases), so really I prefer an HVAC-based solution over a fallback one if possible.

        You mention that the override is cancelled when the occupied setpoint is reached but looking back at the HVAC behaviours this doesn't always seem to be the case. Sure enough the heating demand is stopped when the occupied set-point is reached, but the HVAC continues to follow the occupied setpoint level as it moves higher or lower -- but crucially doesn't seem to drop back to the unoccupied set point. Maybe this is the root cause of my request, and maybe I'm doing something incorrect here which when corrected will solve the 'need'.

        As a specific example, 10 minutes ago I ticked 'presence override' on this particular HVAC. Heat was higher than the unoccupied setpoint but lower than the occupied one. As soon as I ticked the box, the yellow setpoint indicator changed from unocc to occ and the hvac zone demand turned on. The measured temp started to rise (~17.6C) towards the occupied setpoint. On the hour, the occupied setpoint was set to drop from 18 to 17.5C -- ie from above the measured temp to below. The yellow setpoint dropped to still follow the occupied & the zone has turned off, as the room has now reached the setpoint. But the presence override is still on/ticked and the yellow setpoint line hasn't dropped to the unoccupied. I'll try to post some images of it.

        As a side thing, I'd also like a way I can indicate that presence override is on - think : big reminder in the kitchen that we've currently overridden the system. Is it possible to output the presence override status (not aggregate presence).

        Controls:


        Profile: (Override set approx 20:25)
        Last edited by jpdw; 25 November 2009, 10:17 PM.
        Jon

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