Beacon/Morris garage heater venting?

I have a ceiling mount garage heater and would like to run the vent 90° out the back pointing down to the floor then run about 18 inches down then a 90° out the side of building. Is this possible with a power vent and be to code?

In short the vent will drop bellow the appliance before exiting the building. The power vent is capable of running 40ft. The vent length is around 19ft.

http://beacon-morris.com/html/garage_heater_bru.asp

http://beacon-morris.com/modules/lit_lib/download.asp?litFileID=1675