I am in the process of building a motorhome,
I was wondering if some one could help in placement of the furnace and routing the furnace duct, is this done under
the floor, routed through cabinets,etc
any ideas or info would be appreciated.

They seem to put the duct anyplace it will fit. My class C has the furnace under the stove, so the duct goes through the cabinet under the sink and into the bench for the dinette. If you go under the floor, make sure it is well insulated.

When I build my new truck, I'm thinking about running ducts through the floor. You would probably want to talk to an HVAC guy to see how much airflow you will need. If I wasn't going to carpet all the floor, I probably would have experimented with radiant floor heat. Just install an extra diesel fired hot water tank and a pump.

For me, AC is going to be more important than heat. I'm considering going under the floor there too. If I can find some auxillery units like they make for sleepers at a reasonable price.

......1.0 go to all electric heat..put a small electric heater wherever you need the heat and stow the heaters while traveling....duct work looses heat or in case of A/C picks up heat usually because of bad insulation/leakage.....I'd stay away from duct work if I could by using fans and portable unites where ever posssible...A/C is best if used on top of coach-takeing heat off the ceiling cooling it down and dropping the cold air on the passsengers if possible....again use a portable fan it move the air around.....2.0 If you just got to use propane or LNG to heat-put the heating unite at the lowest point of the coach...take cold air off the floor-heat it and blow it on to passengers....If you have an under coach A/C unite you have to take heat off the ceiling suck it down to the cooling unite and pump it back up on the passengers....if you can avoid ducts by using fans-use them!....cheaper -better-faster-better coverage.....moving air causes you to feel 6 degrees cooler because of evaporation from the skin...geofkaye

....one other thing....insulate -insulate- insulate and insulate again.....my trailer only requires a 1500 watt heater to maintain 72 degrees once warmed up....I have a R-15 roof and walls.....geofkaye

In my new Show Hauler we needed to find a ay to cool and heat the sleeper area. I just finished installing a unit made by a company that Dometic just bought out. It seems to be working as advertised.
Here is the Link:
Tundra A/C Unit

Wick

Yep, that's one of the units I've been looking at. I haven't checked pricing yet, a comparable roof unit would be $600 (coleman) to $700 (duotherm). I'm hoping the Tundra isn't too much higher. The Colemans use less power (10.5 amps at 13500 btu). The DuoTherm is basically the same. At 1400 watts per unit I don't see any problem running two 14000 units off of a generator. And that should be plenty. I'm looking at a 22' box with plenty of insulation.

Another one that I've been meaning to check into is made by CruiseAir. It's a two piece unit made for motorcoaches. They claim to have units up to 36000 btu.

FWIW, I'm trying to keep a clean roof. No expensive parts for tree branch target practice. And no reason for anyone to walk around up there.

-lee

.....we took a peice of aluminum 1/4 " thick and bent it like a channel over the top of the ambulance A/C .....it takes OFF the branches now welded a few 1/2" bars like a tree lifter in front and on the rear....no problems now!....My Dometic was $550.00 out the door-installation was done by two girls that work for me-once a guy got the damn thing up on the roof....took all of 1/2 hour after they got the hole opened up.....gefokaye