I can't speak to sharing a
thru hull, I don't know why not, but it seems to be frowned upon, I assume if it was big enough, why not multiple users?
Noise wise it really depends on where it's located, I sleep directly on top of one and can only hear the sound of the air coming out of the vent, I assume the mattress dampens any sound, the other is directly behind the Settee's back, the back cushion agains dampens any
noise, you only hear the air coming from the vent. The Webastos seem a little quieter, my old unit I could hear it's
compressor hum and start and stop, but it wasn't loud. I replaced it with the Webasto as it was getting old and I didn't like the thermostat, I'm spoiled I want to set a temp not turn a knob with no way of knowing temp.
Running the duct work is in my opinion the hardest part, you have to cut large holes for the duct work and of course add ducts or registers, a package unit is literally held down by clips on the pan, run 120VAC to it, wire the
water pump and plumb water to it and another thru hull for the water exit, connect the duct and install the thermostat and your done.
Water pump is not self priming and therefore must be under the water line of course.
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