We camped in the coldest weather we have so far on the past weekend and the temp. got down to just above freezing. The furnace ran non-stop all night and most of the time in the day. I *think* what may be happening is that we had the dealer re&re the coroplast to do a modification underneath and I have a feeling it's not as sealed up as it was from the factory. We're about to take it in for a little warranty work and annual maintenance and will get them to look at it.I've been planning on installing 3 permanently mounted recessed electric heaters (one in each room) and am wondering if we really needed the heated underbelly. All they do is run a furnace duct into the underbelly cavity and let it escape into the outdoors which is not exactly efficient.Is the main purpose of a heated underbelly just to prevent freezing under the floor? How good a job does it really do to keep the floor a bit warmer? We bought a ceramic heater while camping on the weekend and turned the furnace off. My IR gun showed the floor was only a few degrees F colder than walls and ceiling. No heating ducts under the floor except the one to heat the underbelly.We don't plan to ever do any sub-freezing temp. camping so my questions are - if using the furnace, can I cap off the duct into the underbelly or what about installing a damper to cut down the CFM into the space? As long as we camp above freezing, would there be any significant downside to not having a heated underbelly if running on electric heat only? Anyone know if there is a damper available to fit on RV furnace duct (not a vent outlet with integral damper) or something that will attach to the furnace then duct?I have to wonder if the heated underbelly would work that well below freezing anyway when there is a galley tank at the very rear of our TT as well as piping there too and I wouldn't expect air circulation to be that good throughout the space.

With many campers having the furnace provide some hot air to the underbelly is to keep your tanks,(Fresh,Grey & Black) from freezing. I would not eliminate this feature.When we retired and purchased our trailer we thought we would always be in the sun. NOT. We have accidentally been in areas that received snow three times in 8 1/2 years.You just never know.

IN adding your three room heaters you must also keep in mind something must be used to keep the tanks from freezing as well. The furnace is used for this in additional to some tanks have an individual electric tank heater as well.Just don't let your room heater mods get you in trouble of not providing heat for the tanks as well...Roy Ken

I have no belly cover and I get by just fine. But that is the way mine came.Tanks and drain pipes are exposed. I actually added electric heat pads for trips to the snow but I think you are fine if just a slight dip below freezing on occasion.My furnace has replaceable knockouts for each vent. Yours is probably same so easy to delete the vent. Or just redirect into the living space.

We only have a 21 ft TT, but have camped in 39 degrees without using the furnace at all. One small ceramic heater from Tractor supply, on low was plenty.If you are not camping below freezing, the tanks won't freeze.Even if it dips into the high 20's for a couple hours overnight, the tanks won't lose enough heat to freeze.The little ceramic heater was @ $29 and a LOT quieter than running the furnace. IMHO

I have a duct that goes into enclosed underbelly for warm air around tanks etc.I also have a duct that blows into basement compartment.The basement compartment duct has a round register on it that can be fully open/closed/in-betweenRegisterYou can:Remove duct from furnace discharge plenum that feeds underbelly area and put one of the closable registers on discharge duct.We have done winter camping and I am glad of the ducting blowing warm air into basement/underbelly.

Heated underbelly - do we really need ours? | Good Sam Community

30 Replies

myredracer
Explorer II
Nov 18, 2014
Had a look at the furnace ducting today. For the 2014 model, KZ moved the heat outlet grill location for the living area. Instead of the grill previously being inches away from the furnace, the 4" duct supplying it now dives under the floor and runs about 4 1/2' to the new location. The duct under the floor is now under the level of the insulation so it obviously gets cooled before it runs back up through the floor.

This could be one reason the furnace is running so much. It looks like it *might* be straightforward to pull out the existing duct and replace it with insulated duct, or put some duct wrap insulation around it.

I've wondered why the heat coming out of the grill hasn't seemed that warm compared to the old location.

I guess it's just one of those annoying things nobody ever finds out about until you've bought a TT and are using it....
wrenchbender
Explorer
Nov 16, 2014
I have never used the furnace in my present TT. I use a small electric heater. I heat the bath prior to showering with a hair dryer.
kayco53
Explorer
Nov 16, 2014
We love the heated floor.I use mine at the edge of the seasons spring and fall.Have been using it at -8c and it is sure more comfortable than our old trailer with out heated floors.We use the electric heaters when it is warmer so.
Lynnmor
Explorer
Nov 16, 2014
My KZ just had two 2" flexible ducts tossed into the underbelly. I doubt that much warm air would reach to the far ends. It seems to me that there is considerable wasted heat and not much advantage.
myredracer
Explorer II
Nov 15, 2014
aftermath wrote:

Look, it is much simpler than you think. If you are going to camp in cold weather that is ABOVE freezing you really don't need the underbelly heated.

That's what I was thinking. With an insulated floor, I can't see much of a downside. *If* we were to ever go camping in below freezing weather (and that's a big IF for us), it'd probably only be over a weekend and we'd have the TT winterized anyway and would just use bottled water and CG restrooms.

Our first TT was open underneath and had no insulation in the floor and the floor was so cold, even with extra thick socks on, our feet were painfully cold and that was when it was above freezing.

Heated & enclosed underbellies seem to be a bit hyped up and over-rated by manufacturers. Kind of like having special "features" like a bumper with sewer hose storage in it or an outside shower, which cost the manufacturer almost nothing. Being a bit cynical, but the enclosed underbellies also conveniently allows a manufacturer to hide any substandard work at the factory, and possibly gives them a net savings as well.
aftermath
Explorer III
Nov 15, 2014
Wow, lots of advice. Negative draft, positive draft, electric heaters, foam insulation, and on and on.

Look, it is much simpler than you think. If you are going to camp in cold weather that is ABOVE freezing you really don't need the underbelly heated. If, on the other hand, you find yourself out camping when it is in the 20's(F) then having this feature is a very nice thing. Those who live in Southern California probably don't really need heated tanks but if you live in the Northwest you do.

All the electric blankets and space heaters are also a nice option IF you plan to always be hooked up, or like to run your generators 24/7. If you boondock in the cold this won't be a preferable option. Again, don't over think this. Do what will fit your style of camping the best.
JIMNLIN
Explorer III
Nov 15, 2014
smkettner wrote:
JIMNLIN wrote:
I had the dealer add a thermostatically controlled heating blanket under each tank and then encapsulate each tank with foam.
Is this a spray-on foam? If so what product?

Hmmm its been over 15 years but they made a plastic bag around the tanks and filled the bag with expanding foam. I don't remember the name of the foam but I'd bet most long time RV dealer probably know what product was used as it was common practice in this area anyway.
Times change and there may be better expanding foams for that use.
time2roll
Nomad
Nov 14, 2014
JIMNLIN wrote:
I had the dealer add a thermostatically controlled heating blanket under each tank and then encapsulate each tank with foam.
Is this a spray-on foam? If so what product?
valhalla360
Navigator
Nov 14, 2014
myredracer wrote:
One thing I am looking forward to is electric heaters that are quiet. Furnaces tend to be noisy and it's annoying to have to crank the volume up when it's on and down again when it's off. I've specifically purchased heaters that are quiet that have tangential blowers ("squirrel cage") instead of propeller fans. We both have hearing issues and having a quiet heaters will help a lot.

We'll also have more even heating from the front to back of our TT because I'm installing a thermostat in bedroom, bathroom and living area.

I'm installing 1750 watts (15 amps) total and a current sensing relay for load shedding to shut the heaters off when heavy appliance or other loads are turned on. I've been pondering installing a 20 amp power inlet to power the heaters off the 20 amp recept. on a pedestal but not sure yet if it's worth the bother.

valhalla360 wrote:
The furnace shouldn't be running constantantly if you are just above freezing. That shouldn't be happening until you get at least down to around 20f.

Electric space heaters:
- If you electric isn't metered, you cut costs.
- Even if it is metered, there is the hassle of pulling the propane tanks out and hauling them up to get refilled, so the electric heater will reduce how often you have to do that.

When it gets below freezing, we like to set the electric heaters so the furnace still kicks on occasionally at night, so some heat still gets down there and keeps the tanks from freezing.

We have a 1500w space heater and it can keep up down to around 40f at night (though we like it cool at around 65f). Below that and the furnace needs to make up the difference, so 1750 is still in the suplemental range.
myredracer
Explorer II
Nov 14, 2014
One thing I am looking forward to is electric heaters that are quiet. Furnaces tend to be noisy and it's annoying to have to crank the volume up when it's on and down again when it's off. I've specifically purchased heaters that are quiet that have tangential blowers ("squirrel cage") instead of propeller fans. We both have hearing issues and having a quiet heaters will help a lot.

We'll also have more even heating from the front to back of our TT because I'm installing a thermostat in bedroom, bathroom and living area.

I'm installing 1750 watts (15 amps) total and a current sensing relay for load shedding to shut the heaters off when heavy appliance or other loads are turned on. I've been pondering installing a 20 amp power inlet to power the heaters off the 20 amp recept. on a pedestal but not sure yet if it's worth the bother.

valhalla360 wrote:
The furnace shouldn't be running constantantly if you are just above freezing. That shouldn't be happening until you get at least down to around 20f.

Electric space heaters:
- If you electric isn't metered, you cut costs.
- Even if it is metered, there is the hassle of pulling the propane tanks out and hauling them up to get refilled, so the electric heater will reduce how often you have to do that.

When it gets below freezing, we like to set the electric heaters so the furnace still kicks on occasionally at night, so some heat still gets down there and keeps the tanks from freezing.