Array has fewer drives than expected?

I have an old PS4000 that is no longer under warranty and had a failed drive. I decided to "reset" the PS4000 and remove the bad drive assuming that the array will be created fresh and automatically assign a spare. This has not happened and although the array was created its complaining about the lack of drives or what it expected to have installed. Are the equallogics not capable of running with less than a full population of disks? Is there a way I can assign a hot spare since this did not happen automatically? I left slot 15 unpopulated. Is this the slot that the array would normally use as a hot spare?

Thanks

Troy