Class C Furnace inability to maintain coach Temp

[jchantry]

Question: Has anyone experienced the furnace not maintaining coach inside temperature during winter?

2023 Thor Delano 24TT with Surburban NT-20SQ furnace.

During our first winter trip in the new Delano, the furnace was unable to maintain inside temp at 68 degrees. Outside night temp was 16 degrees. The furnace ran continuously but inside temp dropped to 64 degrees by morning.

After returning home and starting troubleshooting found the following:
1. There is no supply air filter, the supply air comes from a floor opening directly to the furnace inlet.
2. The furnace fan ducts appear to be clear and blowing air.
3. The furnace heat (propane flame) is not cycling.

I wonder if the furnace is undersize for these temps?

Thoughts? Thanks

[sbleiweiss]

Many RVs aren't made for 16 degrees. You are doing great keeping 64 inside. If you have electric consider supplementing with electric heaters.

[Mark_K5LXP]

It would be possible to determine the Btu requirement of your RV empirically and see if it matches up to the output of the furnace. Since you observe it's not cycling then it's discharging all it's heat somewhere and it's a fair guess to say you're losing more through the walls and windows than it can supply. Being a recent model I would think Thor would be the one to definitively say what environment the RV is rated for. Given few RV's made are true four season, I would predict if yours is not one of them the response will be anything under 32F and you get what you get. Anecdotally when you read of folks living in RV's in northern states the general theme is increased insulation and supplemental heaters.

Mark B.
Albuquerque, NM

[jchantry]

Mark and Shell - good comments! I've reached out to Thor to determine what the environment the Delano is rated or designed for. I'll post what they have to say. I suspect they will come back with 32 degrees as a minimum.

Did some research and found that a 2022 Delano had a 30,000 BTU/hr furnace installed and that a 2023 Delano came with a 20,000 BTU/hr furnace and less ducting (no bedroom or wet bay ducting)

[d23haynes57]

Originally Posted by jchantry

Mark and Shell - good comments! I've reached out to Thor to determine what the environment the Delano is rated or designed for. I'll post what they have to say. I suspect they will come back with 32 degrees as a minimum.

Did some research and found that a 2022 Delano had a 30,000 BTU/hr furnace installed and that a 2023 Delano came with a 20,000 BTU/hr furnace and less ducting (no bedroom or wet bay ducting)

And probably the only reason for the change was to just save a few bucks. And it was only a few bucks. While 16F is a bit extreme for a travel trailer to be used, it would be nice if the RV manufacturers gave a performance specification as to the temperature design limits, and what the temp rise for winter and cooling capacity is for summer use.

[d23haynes57]

For the fun of it, zi looked this coach up. This is almost 26 feet with a full wall slide out.
No way 20K BTU furnace is enough for temps that low. Especially if it also providing some heat to the water tanks. Possible you can upgrade to a 30K furnace as a drop in. If not on a hookup pay attention to battery usage. Propane consumption probably close to a gallon/4 hours.

[OldBaldFat]

I've found that most Mercedes Sprinter Class C RVs like yours have only 20K btu furnaces, what I consider less than minimal insulation, and very poor distribution systems for the heater output.

That is kind of a trade-off to keep everything within the size, and weight limitations of that chassis. (My 2014 Forest River TT had more weight capacity and a much lower empty weight than the Mercedes Sprinter class of RVs.)

Personally, I do not know of a single MBS Class C that is designed for temps below freezing, in my opinion. A salesman will tell you anything to get a sale, even that the RV is perfectly capable of handling winter in North Dakata.

The manufacturer will tell you slightly different.

Hate to say this, but that type is not designed to 16 degrees.

Suggest you get a 1,200 watt Oil Filled Radiator Heater as a supplemental.

Now, that's going to draw 10 amps of electricity when in use. Make sure you've got the load capacity for that. That RV has only 30 amps maximum usage. Don't push too hard.

And invest in flannel sleepwear and a good down cover for the bed. I also keep my wool watch cap near the bed.

[RVfixit]

My 5th wheel furnace will keep temp at below freezing outside temps but I also use an oil radiator heater for supplement heat. It keeps the chill off and minimizes that amount of time the furnace has to run, especially at night and it saves on propane use.

Safe Travels!

[jl.kauai]

Class C’s are hard to maintain heat. Just curious if you had a blanket or other material barrier to block off cold from cab area. Also make sure your vents are closed on dash and floor as cold air will come. The cab is a major cold zone. Every little bit helps. If you have electricity plug in one electric heater to main floor plugs(usually 15 amps). The find your microwave plug and plug in a second heater as this is a separate 20 amp breaker. Stay warm. Travato John

[SafariBen]

It might seem ridiculous to go from a 30k to a 20k btu furnace in that size, but I bet they had more complaints about uneven heat, than they get complaints about not keeping up with temps in the teens. Saving money was more about the smaller ductwork than the furnace, assuming the furnace has the same features, and similar design, the price difference is peanuts.

[jchantry]

Thanks for the comments.

John - we do hang a blanket across the cockpit just behind the seats. Learned that with a previous Class A many years ago. We did it mostly to keep heat or A/C in the cockpit while driving. Put in the blanket the other night it was so cold. Thanks for the idea of closing the cockpit vents (I didn't think of that!)

All - we did use an electric heater before bedtime and after getting up in the morning. I'm not comfortable running it all night, my Golden Retriever might cause a problem with it.

[Bobby F]

I'm from Minnesota. In every RV I've used in winter, if the temp outside was below 20, we were always bundled up in sweatpants and sweatshirts, and the interior temp was turned to 50. And even then, it would be cold and drafty.


A friend has a smaller tt he uses in winter that stays warm in cold weather, but it was specifically made for that, and it's a $70,000 unit.

[Bill Gail]

We are located in the NW with moderate Winter's , so we camp several times during the Winter .
At times it gets down in the teens at night , and we manage by using the furnace and an electric oil filled radiator.
I added an additional through the wall 110v electrical connection . This allows the radiator to draw power from the 15 amp outlet on the power pedestal . This way the 30 amp service is separate.
I also insulated our front windshield cover and place the radiator between the front captains chairs. Keeps the front of the coach warm and with the passenger rotating captain chair provides additional seating .
The biggest improvements for cold weather camping are the flannel sheets and electric blanket .
Gotta keep the DW warm and comfy.

[Ron Dittmer]

As mentioned by others, the front cab is a very serious heat loss area. I do as they do when temps are uncomfortably cold inside. We throw a quilt across the two front seats and tuck it tight to the side walls to seal off coldest of the cold. That helps a lot. Placing a tiny electric heater just in front of that area, blowing heat rearward, cancels what leaks past along with increasing over-all comfort.

Another thought in reducing heat loss up front is to buy one of those perfect fitting insulated sun shades that fits outside on the windshield and wraps around the side doors like THIS ONE.

One thing certain, the more volume of air from a tall ceiling, a full wall slideout, and a cab-over bed, all work against maintaining inside temps. Single pane RV glass is another significant contributor.

Generally speaking, slide-outs are not cold-friendly. Opened or closed, they seal only so well. Manufacture-dependent, many slideouts are not fully insulated like the fixed walls are. The slideout box is insulated in the main exterior wall, but the sides, ceiling, and floor are a hit or miss. This is why on cold nights, many people do not extend their slideout(s).

But you all already know this.