You can also try this reference:
http://oee.nrcan.gc.ca/publications/infosource/pub/ici/caddet/english/pdf/R285.pdf
Might be worth it to do a search using "dual duct dual fan systems" (DDDF); personnaly, I've always thought about them this way.
Regards,
Frederic Genest, ing., M.Sc.A.
