md,
It does not need to be circuit group. Your problem is your scheduling.
For the IntelliChem (which we do not recommend) to run you must be in the Pool mode or Spa mode.
I am sure your slower speed is assigned to the Pool Circuit. Your High speed does not turn on the pool circuit, You need to have them both on at the same time, so that the Pump/Filter relay is on.
As an example. If you have Pool scheduled to run 8 am until 8 pm and pool high schedule to run from 10 am until 1 pm then this is what will happen.
The pump will come on at 8 am and run your Pool speed, at 10 am the pump will increase the speed to "high" it will stay that way until 1 pm when the speed will drop back to your Pool speed until everything shuts off at 8 pm.
It does this because when the pump sees two or more speeds it will always run the fastest speed.
I don't think your installers have a clue how your system works..
Thanks,
Jim R.