how many IRC5 controllers can you stack vertically

Hi <?: prefix = o ns = "urn:schemas-microsoft-com:office:office" />

If you stack 3 compact controllers it might be a little high to switch to manual and auto mode on the top one. I had just 3 drive units and one control unit where I put the control unit as second module from bottom. The ABB support people didn't like it very much. The access to the top drive unit is only possible with a ladder, but there is no need for that.