Heating the underbelly when it's not cold

[RV-burrito]

We have a '17 Sprinter that we live in full time while we build our house. I've been customizing things to our liking. I have no intention of ever selling it so any mods don't need to consider resell value, just quality of life improvements.

My question is: If I have the thermal package that adds extra insulation (barely) and the heat ducts that point down as well as up (heating the enclosed frame area with the tanks and whatnot) why shouldn't I rig up an override to the ducting system that closes off heating the underbelly when there is no danger of freezing? If it's only 50 degrees and I want to take the edge off inside there's really no reason to waste propane heating down there. I'm just trying to find some ways to stop throwing money out the window.

Thanks!

[JRTJH]

The "technical reason" is because the "DC powered furnace" can easily overheat if the output air from the heat exchanger is restricted. In other words, shutting off heat vents can cause the furnace to overheat and go into "lockout".

Second, and to address your concern about "throwing money out the window"... The RV furnace is one of the most "inefficient furnace designs" yet to be outlawed in home use. Most RV furnaces are around 50% to 60% efficient. You can go outside and put your hand near the furnace vent to see for yourself. On any RV furnace that I've seen, after a couple minutes of operation, the exhaust vent is so hot that it will blister your hand if you touch it. So, just operating an RV propane furnace is "throwing money out the window".....

If the temperature is high enough that you just want to take the chill off the interior, you might consider using an electric space heater or install a propane catalytic heater. Both keep 100% of the heat inside the trailer rather than "blowing half of it out through the exhaust".

Something else to consider: The heat ducts in the floor of any RV are not insulated. That is by design. The underbelly is not "heated by a 2" duct" (that does help, but can't heat that much uninsulated belly space)... Rather, much of the heat in the belly comes from heat transfer through those "meandering around obstacle" mylar dryer vents. There's a reason they are "too long with lots of wasted curves"... It's so they wrap around tanks that need to be heated. If you try to shut the heat flow through those ducts, you won't have heat in the bathroom or bedroom either.

Honestly, any RV with 2" R-9 walls, single pane windows, holes around every slide, open, unsealed holes in the floor and an uninsulated steel frame filled with holes that allow cold air into the belly and holes in the belly that allow that air to enter the trailer around every water pipe... Well, suffice to say that RV's aren't energy efficient or energy saving structures...

Just trying to heat a trailer with single pane windows is "throwing money out the window"....

I don't mean to sound "defeatist" in trying to save money when living in an RV, but cutting off heat to the belly when it's not going to freeze comes with the possibility of triggering your furnace "high temp limit switch" and probably won't save much money in the long ruin.

[Ribtip]

Originally Posted by RV-burrito

We have a '17 Sprinter that we live in full time while we build our house. I've been customizing things to our liking. I have no intention of ever selling it so any mods don't need to consider resell value, just quality of life improvements.

My question is: If I have the thermal package that adds extra insulation (barely) and the heat ducts that point down as well as up (heating the enclosed frame area with the tanks and whatnot) why shouldn't I rig up an override to the ducting system that closes off heating the underbelly when there is no danger of freezing? If it's only 50 degrees and I want to take the edge off inside there's really no reason to waste propane heating down there. I'm just trying to find some ways to stop throwing money out the window.

Thanks!

Maybe put in another register off that line so you can go either way. Dw has a throw rug over one of ours in our 327res dosen't seem to ever cause a problem. I think adding one would be cool so you could go either way. Post back with your solution.

[sourdough]

First, IMO, if you buy an RV you're "throwing money out the window" more or less. One hopes they can get enough out of it to make it worthwhile but in the end they just aren't made to save money any way, shape, fashion or form as has been mentioned.

My trailer heats inside and the basement as well and I like it that way in the event it's needed. I don't like the irritation of pulling the LP tanks when empty, drive to town, wait to fill them up then come back and install them. To that end I run one Lasko tower heater (electric) right beside the fireplace set to a temp that keeps the entire RV comfortable (if it's not below 40 or so). I could use the fireplace but this one came with a junk Furrion (my opinion) that won't allow you to turn the flame off as I could with my last one so I rarely use it. I do run the heat pump from time to time as well.

We've been on this trip for almost 3 mos. and I've filled one LP tank once....and it left home 1/2 empty. That probably wouldn't have happened but I'm running the water heater on strictly LP since the AC side has a problem. Seems the tiny bit of money, if any, you would save by trying to modify the ducting wouldn't be worth the effort of modifying the duct system and the possible future issues that may or may not cause. JMO

[jasin1]

I’d also add if it haven’t been mentioned that your not wasting as much heat as you think…heat rises and the uninsulated floor is getting warmed up as well as the basement itself…that heat finds its way into the living space indirectly...if you try and change the duct layout you may find the floors are a lot colder then you would like.

[dutchmensport]

In non-freezing temperatures, we just use space heaters and the electric fire place built in the camper (it's just a glorified space heater).

[NH_Bulldog]

If you are not concerned with heating the underbelly, dollar for dollar your least expensive heat option is an electric space heater.

[MN Doughboy]

A warm floor is better than a warm roof...