switched supply and return

for a Beacon Morris toe kick heater running on a monoflow system. I was helping a friend install one on his system using the existing monoflow tees, and the original installers used the monoflows "backwards" i.e. the monoflow tee is on the supply, and the standard tee is on the return (I've seen them done both ways).  I should have studied the system a bit more before I did the job, oh well.  Is there any sort of check valve in these heaters that would cause a major problem?  This is for supplemental heat only, and we have not tested it yet because we still have more work to do on the system.  Thanks!



-Mike