Under my helm seat had the right sized space, heater above fuel tank which seemed the easier install, and a louvered vent for return air. All I did was put a household return air filter behind the louvers.
As for outside fresh air makeup..I'm still torn as the outside air is often as humid as the inside...and like most boats far from air tight anyway. Though I may try a fresh air makeup...but for space reasons I will have to make a fiberglass junction box to go over the air intake that will do a quick 180 with minmum clearance.
Wallas said that a filter wasn't all that necessary because there is plenty of "open" area on the bottom of the furnace that can allow "unfiltered air into the furnace.
Greeting- Purchased a 30dt yesterday. Looking for information on installations when your post regarding location. A question: The dealer seemed to stress the need for one of the air inlets to be fed fresh air. Our boat configuration really doesn't have a "friendly" location outside of going through the hull with a dedicated inlet like an engine room air intake. It appears that you have configured a filter system within your pilot seat that uses cabin air for both air inlets. If this is the case, how does it differ from having outside air, if you have thoughts? My current Espar, which is being replaced, has one air inlet and that is cabin air. The resulting hear is sufficent. I understand that there is two different processess involved between the two manufactures.
Anticipating your good response, I remain,