What's a Loxone and why does the stupid thing have such a low input impedance? The reason is this chip. HVS882. It's an industrial input serializer chip. The input impedance is only 10k. This chip operates in a "window" mode for detecting "on" vs "off". With the recommended 4.7k pullup on a 24V supply, this leaves things very close to the 16V threshold that the chip requires for an "on" state. So I've started using 3.9k pullups which gives a little more room for movement on longer cable runs where a few volts can potentially be lost bringing it under the required 16V.

I built an aircon mount today. It is a cantilevered design that holds the AC in and is secure, but does not screw into the house or into the window frames at all. The house is rented, so there are rules preventing us from fixing it permanently to the structure.