iMac ejects external drive when it sleeps

I have a late model 2012 iMac running El Capitan 10.11.3 and I've just purchased an OWC USB 3.0 External drive. Every time the computer sleeps, it improperly ejects the drive. OWC thinks it's in El Capitan. It seems like a lot of people are having this issue but no real solution. I've reformatted the drive, replaced the drive, set it up so it hard drives never slee, but within a minute of sleeping, the drive light goes out and won't remount itself.