When Upgrading the ISY-99i to the ISY-994i, Should I Purchase the "Pro" Version?

Besides the number of additional links / programs that the Pro version of the ISY-994i supports, there is one particular feature that helps you save time when programming and setting up an Insteon system. That is the "delayed write" feature, that allows you to save and queue up Insteon device configuration changes between writes to the devices.

To illustrate - every time you make a system configuration change - adding a device to a scene, removing it, adding a device, and so on - the link tables on those devices need to be updated over the Insteon network. The PLM attached to your ISY-994i sends commands, over your powerline / wireless Insteon mesh net - communicate with the device in question, and sends the information required for that device to update its links tables.

Even a relatively minor change normally takes 10 or 15 seconds for this updating to take place. During that time, you can't interact with the administration console of your ISY-994i. So, you're waiting for it to finish. If you are modifying a scene with many Insteon devices - say - your 'All Indoor Lights" scene - this process can take a couple of minutes, up to 5 minutes if you have a large number of devices.

With the delayed write feature on the ISY-994i enabled - you can make all your changes to your scenes, rearrange your assignments.  Once you've finished making your configuration changes - you then toggle the delayed write button on the ISY-994i - and then it will make all the writes, to all the affected devices - all at once. This ends up being a significant time saver once you end up with a significant number of devices. If you're starting out, and only have a dozen switches and keypads, it may not be worth the extra cost. If you have 50 to 100 devices, there is no question, this will save you a lot of time.