When setting up my Insteon can lights with Insteon scenes, I had a revelation that might seem obvious, but is worth mentioning because I know I spent a lot of time pulling my hair out on this one. In a nutshell: because Insteon builds a peer-to-peer mesh network, Insteon scenes are not stored in any single device. Instead, they’re stored in link tables on each device, including the ISY994i (or, more specifically, the PowerLinc Modem, a.k.a. the PLM).
Why does this matter? Well, when I turned on my new scene the first time through the ISY, the dim levels in the lights were all set properly to 50%:
But then, when I used one of the switches in the scene, the lights came on at 100%. This drove me nuts, thinking that the lights weren’t compatible with setting dim levels at scene activation. Then I realized each device keeps it own copy of the scene settings in its link table, containing the addresses and dim level of the other devices in the group. They don’t necessarily all have to be the same. For example, when I expanded the scene and clicked one of the devices under it in the ISY, I could see that the dim level for that scene (set via that device) was 100%:
So, in practice what this means is that you don’t have just one “scene”, you have a separate scene (a.k.a., an Insteon “group”) stored on every device, and if you’re having unexplained issues you might want to check that they are in synch. Fortunately the ISY makes this easy with that big fat “Copy Scene attributes from <SceneName>” button, which appears when you click each individual device under the scene in the tree on the left.