Hi Brian my Webasto 2010 45,000 Btu unit has 3/4 inch outlets and I have one loop that feeds 5/8 hose. Paul
My bus had a 80,000 BTU Webasto originally and that may be the reason for the 1 1/2" feed to the Webasto. I want to be sure that if use a plate exchanger with 1" fittings that I won't be restricting coolant flow too much. I believe the coolant line to the Webasto went first to the passenger/driver heat so I suppose it isn't an important line. Everything except the driver's heat and defrost is longer gone.
I think I'll be okay.