Furnace Tradeoffs

 I'm sorting through the options for the furnace in Decatur. I think the primary requirements are:

• roughly 20k BTU heating capacity (I've read 1k BTU per foot is recommended)
• propane fueled
• needs to fit into ~13 inch wide space, height is less critical
• minimized external appearance (no external door - means it must be installed from inside)

I used a Propex HS2000 in my Boles Aero but the Boles has a very small interior. The Propex is only 6 kBTU but it's a real easy install and has no obvious external appearance (it exhausts through the floor vs the wall). Truthfully I've never had to use the Propex unit while camping so maybe my 20 kBTU requirement is overkill but I think it'll provide peace of mind for any shoulder-season camping we might do.

Here's a list of options with pros/cons that I've come up with:

Suburban NT20-SEQ, 19 kBTU

Pros

• Small size: 9.5" H x 9.5" W x 22.5" D
• Relatively light weight (22 lbs)
• Easy install
• Probably the cheapest of these alternatives

Cons

• Single duct and/or direct vent
• Larger external vent (2 holes for Suburban models vs 1 for Dometic)
• Internally visible (intake) panel required
• Can't easily upsize later if we find that 20 kBTU is insufficient

Suburban NT-20SEQ, Direct Vent

Dometic DFSD20121, 18 kBTU, small size cabinet

• Pros
• Small size: 7" H x 12" W x 20" D
• Can be installed vertically as well as horizontally
• Relatively light weight (20.8 lbs)
• Small external vent (single vent hole vs 2 for Suburban models)
• 2 (min) + ducts (for front and back of Decatur)
• Vent location selection easily accommodates horiz or vert installation
• No internally visible (intake) panel required
• Cons
• Can't easily upsize later if we find that 18 kBTU is insufficient
• Pricy and seems to have limited availability (note: 20111 models readily available and cheap but require large external door).

Dometic DFSD20212, Small Case, Small Vent

Suburban SF-20FQ, 19 kBTU medium sized cabinet

Pros

• 2 (min) + ducts (for front and back of Decatur)
• Vent location selection location not as good as Dometic
• No internally visible (intake) panel required
• Medium size furnace cabinet size could be swapped for unit with up to 35 kBTU if needed later

Cons

• Larger cabinet (7.5" H x 17" W x 20" D) size requires vertical installation
• Added cost of vertical installation kit
• Larger external vent (2 holes for Suburban models vs 1 for Dometic)
• 29 lbs
• Less expensive than medium sized Dometic unit

Suburban SF-FQ Series Furnace, Medium Cabinet

Dometic DFMD 20121, 18 kBTU medium size cabinet

Pros

• Small external vent (single vent hole vs 2 for Suburban models)
• 2 (min) + ducts (for front and back of Decatur)
• Vent location selection easily accommodates horiz or vert installation
• No internally visible (intake) panel required
• Medium size furnace cabinet size could be swapped for unit with up to 35 kBTU if needed later

Cons

• Larger cabinet (7" H x 16.5" W x 20" D) size requires vertical installation
• 35 lbs
• Pricy

Dometic DFMD20121, Medium Cabinet, Small Vent

Each of these options has some installation requirements that need to be considered before a final selection can be made. For example the cabinet dimensions need to accommodate side and top clearances depending on the orientation (vertical or horizontal) of the furnace.

Right now I plan to install the furnace in a small closet between the kitchen area and the bathroom. I think it will be about 13" wide. This won't provide much clearance area on the sides so a vertical orientation may be required for even the small Dometic 20121. Given these constraints either the Suburban NT-20SEQ or Dometic 20121 are leading contenders.

The NT-20SEQ is attractive because it's small and cheap. It also has the least cabinet interior mounting restrictions (5/8" clearance from the top and sides). It also has a duct/vent on the left side that could be plumbed into the bathroom to assist in drying. The downside is the front direct discharge which isn't attractive and will force a fixed cabinet door (but would simplify ducting installation).

The Dometic 20121 is attractive because of the ducting options and the small exterior vent. It also doesn't require a front vent. But it will require a lot more cabinet real estate and may not be possible given the installation requirements: 3" required clearance on each side plus the 7" width of the furnace may be more than is available. The Dometic may also be a lot more expensive and possibly unavailable.

Before I can lock down a decision I'll need to get a bit further down the road and nail down the floorplan and cabinet dimensions. Given what I know it appears the NT-20SEQ is the leading candidate.