If you use a clamp on meter around two wires, like a power cord, it will read zero amps ac or dc. This is because equal amps are flowing in opposite...
this blowing conditioned air outside kind of puts the lie to a sealed house saves energy. Do all you can to seal air leaks then use a powered blower...
I think the secondary is just dripping into the crawlspace. There is hardware cloth around the floor so combustion air can come from the crawlspace....
I think the OP may be confused about airflow. It does not matter where the DC is located, inside or outside, if it is exhausting outside it is still...