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Thread: Opening a skylight based on temperature

  1. #1
    Automated Home Sr Member
    Join Date
    Jul 2004
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    55

    Default Opening a skylight based on temperature

    Hi all,

    I've left the system alone for a while, but I've just had the urge to have a fiddle again!

    I've interfaced the heatmiser thermostats to Cortex (via XaP) so I can now see the temperature in each room and whether the heating is on. In a couple of rooms I'd like to open the skylight if it gets a bit hot (chance would be a fine thing). The skylights are already happily on motor control.

    I was looking for something like "open the window if the temperature is greater than 24C and the heating is not on. Close the window if the temperature falls or at 9:00pm regardless". I'm sure I can do this with thermostat thresholds and some general logic. I was thinking it might be more elegant to use the fan control object as I think that gives me all I want (time windows, threshold, and if I connect the "heating on" input to the fan block input the heating inhibit).

    Any views, better solutions?

    pbj

  2. #2
    Automated Home Legend Karam's Avatar
    Join Date
    Mar 2005
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    817

    Default

    What kind of drive do the skylights require? I.e the fan object will normally switch the relay ON to energise the fan and vice versa. I suppose if the skylights operated by permanently switching live (or neutral) to one of two terminals then a changeover relay might have the desired effect. I haven't thought it fully through but sounds like a nifty idea if it works out this way, otherwise as you say, some macro/logic is the alternative.

  3. #3
    Automated Home Sr Member
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    Jul 2004
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    Default

    Thanks Karam. The skylight is currently connected to a motor control object (it's a 24v polarity type drive) which works well. I've had a little test connecting the fan state output to open on the motor control and "not state" to close. It seems to work well. Does the fan object have any form of hysteresis? I guess it could cause problems if the temperature fluctuates around the set point (although I guess I could use "not state delayed" connected to close to give me approximately the same thing.)

  4. #4
    Automated Home Ninja Viv's Avatar
    Join Date
    Dec 2004
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    284

    Default

    Quote Originally Posted by pbj View Post
    Does the fan object have any form of hysteresis?
    Currently no. However next update will provide a user selectable value.

    Viv

  5. #5
    Automated Home Sr Member
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    Jul 2004
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    Default

    Thanks Viv.

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