About hybrid water heater condensation and power requirement

critterdoc

We have an early 70's Kohler oval bathtub which holds in excess of 100 gals and the current 50 gal gas hot water heater is simply not up to the task. Tankless is not possible because of the 1/2" gas line and there is no possible way to rerun a 3/4 gas line without major mods to the flat roofed structure, and maximum functional width of the heater closet is 24" which greatly limits tank capacity.

I was pleased to recently discover the A. O. Smith GDHE-50 Vertex GPHE-50 and GDHE-50 condensing hot water heaters and would appreciate advice on several questions:

1) How much condensate is expected per unit of time when the heater is operating, how does it exit the device and can it be gravity drained to the outside of the house through a floor level hole which could be drilled in the outside wall which would be very close to the side of the heater? The unit would be placed in a pan which would also be drained outside through the side wall at floor level.

2) The utility closet that houses the current heater has two louvered outside doors that worked well for the now defunct 50 gal Rheem unit. Will these louvers provide adequate provide intake air or must we run a vent through the outside wall or the flat roof for that purpose?

3) How much electrical power will these power-vent heaters require to function?

4) What is the difference between "Power-Vent" [GPHE-50 ] and "Power Direct-Vent" [GDHE-50 ]?

Many thanks...