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sebbacon / home-automation

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Handle boiler switch failure mode #1

Closed sebbacon closed 6 years ago

sebbacon commented 6 years ago

As the boiler switch is controlled by via OpenHab on the Pi which itself goes through the MAX cube, things that might go wrong:

In all these cases, if it stops working with the boiler turned off, and we want heating, then we have trouble. Solutions:

  1. Boiler override switch on Pi. This will deal with openHAB or network failures
  2. Ensure on power failure that the relay defaults to closed. I think this means switching to the NC terminal on the relay.
sebbacon commented 6 years ago

If I use the NC terminal, then all the UI and rules in openHAB will invert.

One solution to this is to create a "real" switch and then a "proxy switch" with a rule that inverts the switch state between the two, and use the "proxy switch" in UI and other rules.

sebbacon commented 6 years ago

The NC terminal didn't work. The relay still needs power to maintain the closed state.

I used a physical switch that can override the Pi by shorting the circuit (i.e. wired in parallel with the Pi)