Forum Discussion

darla_m's avatar
darla_m
Explorer
Jul 10, 2020

old furnace replacement help on ducts?

Hi all, first I had fresh water tank questions, now I'm onto furnace questions...

Restoring old holiday rambler 25' trailer from late 70s. Furnace doesnt seem to work (have 12v power and gas hooked up, when I turn on thermostat absolutely nothing happens). Figured I'd be better off replacing it anyways. It's an old suburban.

Found someone selling a new from last year suburban on craigslist and looks like it will fit the space/heating capacity etc however, MY old furnace is ducted directly into the floor via a rectangular "mouth" cut out of the bottom. This goes into three separate ducts to heat the rest of the trailer.

The one he's selling (a Suburban NT20SQ) has holes in the side for ducts.

I'm a first time RV owner so I don't even know if they make furnaces like mine anymore that vent into the floor?

I would really appreciate any insight anyone might have to offer on how to convert/adapt/etc. I can't really do much floor modification at this point, so would really like to not have to cut new holes etc. Would it be completely insane to cut a hole out of the bottom of the new furnace to line up with the hole in my floor?

Would appreciate any advice! Thanks
  • CavemanCharlie's avatar
    CavemanCharlie
    Explorer III
    Jul 11, 2020
    darla_m wrote:
    Hi all, first I had fresh water tank questions, now I'm onto furnace questions...

    Restoring old holiday rambler 25' trailer from late 70s. Furnace doesnt seem to work (have 12v power and gas hooked up, when I turn on thermostat absolutely nothing happens). Figured I'd be better off replacing it anyways. It's an old suburban.

    Found someone selling a new from last year suburban on craigslist and looks like it will fit the space/heating capacity etc however, MY old furnace is ducted directly into the floor via a rectangular "mouth" cut out of the bottom. This goes into three separate ducts to heat the rest of the trailer.

    The one he's selling (a Suburban NT20SQ) has holes in the side for ducts.

    I'm a first time RV owner so I don't even know if they make furnaces like mine anymore that vent into the floor?

    I would really appreciate any insight anyone might have to offer on how to convert/adapt/etc. I can't really do much floor modification at this point, so would really like to not have to cut new holes etc. Would it be completely insane to cut a hole out of the bottom of the new furnace to line up with the hole in my floor?

    Would appreciate any advice! Thanks


    I think you could do that. Without seeing the whole thing it's hard to tell. You would need to Plug the old holes in the furnace after you cut a new one.
  • jdc1's avatar
    jdc1
    Explorer II
    Jul 10, 2020
    Touching the two wires together is the correct way to see if the blower motor works.
  • darla_m's avatar
    darla_m
    Explorer
    Jul 10, 2020
    Please forgive me but what does TT mean? TT wall?

    I had run new thermostat wires (one red on white) cause old ones were chewed through. reconnected them in the correct way (at least i'm 95% sure unless there was something amiss on the original.) wired them to furnace. checked for power/continuity with multimeter. My understanding is that these old thermostats work like switches that basically make a closed circuit when it reaches a certain temp? so i tried directly touching white and red wires to see if it did anything. Nope.

    Any other things I could try for testing the old one? No one in town will come look at it i would have to bring the RV out of town but unable to tow at the moment.
  • bucky's avatar
    bucky
    Explorer II
    Jul 10, 2020
    WE had an older TT when we started out years ago. There was a very small almost invisible tab on the bottom of the Tstat that also had to be in the right position. Worth checking.
  • Huntindog's avatar
    Huntindog
    Explorer
    Jul 10, 2020
    darla m wrote:
    Would it be completely insane to cut a hole out of the bottom of the new furnace to line up with the hole in my floor?
    That would be the way I would do it.

    Make sure you measure many times befor cutting. You need to be sure that the inlet/outlet to the combustion chamber lines up with the holes you already have in the TT wall from the old furnace

About Travel Trailer Group

44,029 PostsLatest Activity: Jan 28, 2025