Thanks Rmw for your reply.
My experience is the same, i.e. more "A" cases rather than "B".
Btw, can you recall what heat recovery was in those cases?
I am doing a utilities system efficiency check where Eco giving 20-23deg.C heat recovery and flue gases leaving the stack stay ~170-190 deg.C. To me heat exchange is too low and stack temp it too high!
That's why I led me to think that in my particular case, scenario "B" would give a better duty.
Thought?
Thanks.
I_mak