Truma Varioheat Furnace Retrofit Install in All Terrain Camper

[ski3pin]

The Truma Varioheat propane forced air furnace is touted to be the latest and greatest. It gets outstanding reviews. What’s the truth? I’m game for jumping in and trying things. One big problem. They are not sold for aftermarket installation. They are sold to manufacturers for installation in new Rvs. Regular Truma dealers around the country cannot purchase a furnace for resale or installation by their techs. Truma offers sale and installation in other RVs only at four sites across the US. One is their headquarters in Indiana and three other locations using mobile installers. With no ill intended and not saying I’m the best at everything or anything, some of the installs I’ve seen told me I would not let them touch my camper. Also, I did not know if one would fit in our small camper.



Here's the messy part. I found a unit for sale along with installation parts, instructions, and helpful advice. I expect Truma could be unhappy with this. Enough said. I don’t recommend you do this. I went ahead knowing that I’m completely on my own and expect I would not have support if the unit fails sometime in the future. I’m trusting in that much touted fine German engineering.



Once I had the unit in hand, I saw I could mount it where the Atwood furnace was installed by ATC. This is right where I wanted it. Hot air rises so I like it starting near the floor.



Out with the old.

The exhaust port can be mounted through wood, so I filled the gap.

That’s full thickness plywood in the bottom section and 1/8” plywood at the top. The top gap will be filled with insulation. I made a trip down to All Terrain Campers to have new siding placed over the exterior.

The above photo shows the hole for the exhaust port but also shows the simple bombproof bracket installation to mount the furnace to the floor – strips of 1/8” aluminum angle. The seller suggested this to me and provided a photo on how he mounts this way.

Looks great, doesn’t it? Marty and the guys at ATC do top quality work and know campers inside and out. These guys I trust.

 

[ski3pin]

Back home, Julie and I figured out final mounting and installation. Here’s where it’s going and the plywood is a template for the warm air outlet from the front (at least what I’m calling the front) of the furnace.

Here’s new ply for the furnace enclosure with two inlets for the cool air intake to the warm air chamber in the furnace. Note: the cool air intake on the furnace is below the hot air outlet at the front of the furnace and an inch or so back. That can be seen in the photos above.

To mount the furnace to the floor I used four stainless hex head 1/4x20 machine screws with T-nuts on the exterior of the floor pack plywood. It is solid and simple.

I felt the remainder of the installation was straight forward. The burner exhaust is a small diameter flex metal tubing. I believe (don’t trust me, check for yourself) the minimum exhaust length is 12” with a max of 48”.

The burner inlet air is a larger diameter flex tubing.

Truma provides a straight forward electrical connection box.

Although not pictured, there are three electrical connections. One – power and ground. Two – a telephone type wire to the back of the control panel (the control panel also requires a separate power and ground). Three – a two-wire line to the temperature sensor that I mounted in the cabinet near the control panel.

Here’s the temperature sensor to the right of the Truma control panel in our new camper.

Another reason I wanted the new Truma furnace in the old furnace location was there was already a propane service line.

Here’s the finished exterior.

Note: for the heated air outlet (top photo) I used a short length of flex tubing to join the furnace outlet to the louvered plate. You can rotate the louvered plate to direct airflow. That pictured loose led light strip has been replaced.



How do we like the furnace? We used it for seven months in this camper. We liked it well enough to install one in our new camper. Total, that’s a full year of using a Truma Varioheat furnace. And that’s a lot of nights – we already have 87 nights in the new camper.



Is it perfect, the silver bullet? Of course not. I’m a hard grader. From 1 to 10, the old Atwood I’d rate at 6. The Truma I rate at 8.5. It is a very good furnace and we really like it. It operates at various levels (the name says that, right?) as it heats up the camper. Here’s what it’s like for us in the morning and the interior of the camper is 34°. We do not heat the camper overnight, unless it will freeze hard, then we run the furnace on the lowest setting (Truma is 40°). Control panel has a timer setting. It starts at 5:30 with the desired temperature set at 62°. The furnace starts up – blows air through the burn chamber to clear it, ignites, burns for a few seconds, and roars to life. It is loud. The exhaust is also loud outside the camper. It is a bit louder than the old Atwood. It goes to work quickly heating the interior. A few minutes later the burner shuts downs and the fan continues moving air through the chamber. The burner reignites at a lower level and the circulating fan operates at a lower level. A few minutes later this is repeated until the furnace steps down and runs at a very quiet level. With the fan now running low, we are not blasted with warm air like we would experience with the Atwood, which accentuated the feeling of a “hot - cold” cycling.



In the “Con” column is the control panel. It is overly complicated. It’s built to run other Truma appliances also, so I don’t know if there’s a solution. It takes several button (Select) pushes and a turn of the dial to turn the furnace on. Julie’s head is not built for technology. I’ve put together a cheat sheet to help her. A simple “on” and “off” would work well for her. Another complaint is that – unlike thermostats most of us are used to – the control panel never displays the current temperature in the camper, only the temperature you’ve set. I do not know the temperature the control panel is reading. Another complaint is I’ve found there is no reference to what the temperature differential is or if it can be adjusted. From our use it appears to be – at the most – two degrees. Note: we have a separate “Inside” “Outside” temperature display on our counter.



Note: my observations above are based on having the fan set to “auto.” There is a fan setting “night” that is said to be very quiet – in fact the instructions warn the unit is running so low it may not hit your set temperature. We’ve not tried it as we don’t run the furnace when asleep and the noise level – once it’s gotten the camper up to the set temperature – is comfortable.



Bottom line, we liked it so well this is what I installed in the new camper.



I hope those of you that are curious about this furnace find my installation and experience with using it helpful.

 

[rjap]

My 2025 Hawk has the VarioHeat. If limited to only one option to add to a base model camper, the VarioHeat would be my choice. What a pleasure to have a warm and dry space! Clever how it captures heat from the exhaust and electric motor to feed back into the output in the camper.

With PNW winter temps in the 40-50ºF range and the VarioHeat set to 70ºF evenings and nights, my Hawk, with the thermal package, can go 6 days/nights on one 10 lb propane tank. This includes light usage of the stove and AquaGo water heater as well as venting through the ceiling fans on low.

I have not tried a setting of 40ºF overnight. It would likely add significantly to propane autonomy.

At a set temperature of 70ºF, the temperature measured at the front dinette with a multimeter thermocouple shows a range of 66ºF to 72ºF before the VarioHeat turns on or shuts down. This likely depends on how I direct the furnace and vent airflows.

The furnace has three output levels, and seems to "upshift" to the lower/quieter settings as soon as it can, favoring longer times on low/quiet in lieu of short bursts on high. No doubt the clever engineers at Truma have tuned it to economize on propane and battery consumption.

 

[kmcintyre]

Great write up! Thanks!

 

[Defulmmt]

Thanks, great information. One question, where did you terminate the combustion air intake? Is it in the area around the front turnbuckle?

 

[ski3pin]

Thanks, great information. One question, where did you terminate the combustion air intake? Is it in the area around the front turnbuckle?

The combustion air intake is part of the exhaust port at the back of the camper.

 

[Defulmmt]

Thanks again, I think I understand the setup. The exhaust combustion pipe is installed inside the air intake piping and the both terminate, with separate connections, to the exhaust port. I like this design much better than the Propex furnace.

Only problem is trying to find these units for retrofit.

 

[ski3pin]

Yes, the center of the exterior exhaust port is the exit for the combustion gases. The combustion intake comes in on the sides. I'll see if I can find a photo to illustrate.

 

[ski3pin]

Thanks again, I think I understand the setup. The exhaust combustion pipe is installed inside the air intake piping and the both terminate, with separate connections, to the exhaust port. I like this design much better than the Propex furnace.

Only problem is trying to find these units for retrofit.

Here are three photos I sourced off of the internet that may help illustrate the combustion intake and exhaust.

 

[Vic Harder]

that's super slick.

 

[Casa Escarlata Robles Too]

Great idea it per heats the intake combustion air.
Frank

 

[softwaremom00]

Back home, Julie and I figured out final mounting and installation. Here’s where it’s going and the plywood is a template for the warm air outlet from the front (at least what I’m calling the front) of the furnace.

Here’s new ply for the furnace enclosure with two inlets for the cool air intake to the warm air chamber in the furnace. Note: the cool air intake on the furnace is below the hot air outlet at the front of the furnace and an inch or so back. That can be seen in the photos above.

To mount the furnace to the floor I used four stainless hex head 1/4x20 machine screws with T-nuts on the exterior of the floor pack plywood. It is solid and simple.

I felt the remainder of the installation was straight forward. The burner exhaust is a small diameter flex metal tubing. I believe (don’t trust me, check for yourself) the minimum exhaust length is 12” with a max of 48”.

The burner inlet air is a larger diameter flex tubing.

Truma provides a straight forward electrical connection box.

Although not pictured, there are three electrical connections. One – power and ground. Two – a telephone type wire to the back of the control panel (the control panel also requires a separate power and ground). Three – a two-wire line to the temperature sensor that I mounted in the cabinet near the control panel.

Here’s the temperature sensor to the right of the Truma control panel in our new camper.

Another reason I wanted the new Truma furnace in the old furnace location was there was already a propane service line.

Here’s the finished exterior.

Note: for the heated air outlet (top photo) I used a short length of flex tubing to join the furnace outlet to the louvered plate. You can rotate the louvered plate to direct airflow. That pictured loose led light strip has been replaced.



How do we like the furnace? We used it for seven months in this camper. We liked it well enough to install one in our new camper. Total, that’s a full year of using a Truma Varioheat furnace. And that’s a lot of nights – we already have 87 nights in the new camper.



Is it perfect, the silver bullet? Of course not. I’m a hard grader. From 1 to 10, the old Atwood I’d rate at 6. The Truma I rate at 8.5. It is a very good furnace and we really like it. It operates at various levels (the name says that, right?) as it heats up the camper. Here’s what it’s like for us in the morning and the interior of the camper is 34°. We do not heat the camper overnight, unless it will freeze hard, then we run the furnace on the lowest setting (Truma is 40°). Control panel has a timer setting. It starts at 5:30 with the desired temperature set at 62°. The furnace starts up – blows air through the burn chamber to clear it, ignites, burns for a few seconds, and roars to life. It is loud. The exhaust is also loud outside the camper. It is a bit louder than the old Atwood. It goes to work quickly heating the interior. A few minutes later the burner shuts downs and the fan continues moving air through the chamber. The burner reignites at a lower level and the circulating fan operates at a lower level. A few minutes later this is repeated until the furnace steps down and runs at a very quiet level. With the fan now running low, we are not blasted with warm air like we would experience with the Atwood, which accentuated the feeling of a “hot - cold” cycling.



In the “Con” column is the control panel. It is overly complicated. It’s built to run other Truma appliances also, so I don’t know if there’s a solution. It takes several button (Select) pushes and a turn of the dial to turn the furnace on. Julie’s head is not built for technology. I’ve put together a cheat sheet to help her. A simple “on” and “off” would work well for her. Another complaint is that – unlike thermostats most of us are used to – the control panel never displays the current temperature in the camper, only the temperature you’ve set. I do not know the temperature the control panel is reading. Another complaint is I’ve found there is no reference to what the temperature differential is or if it can be adjusted. From our use it appears to be – at the most – two degrees. Note: we have a separate “Inside” “Outside” temperature display on our counter.



Note: my observations above are based on having the fan set to “auto.” There is a fan setting “night” that is said to be very quiet – in fact the instructions warn the unit is running so low it may not hit your set temperature. We’ve not tried it as we don’t run the furnace when asleep and the noise level – once it’s gotten the camper up to the set temperature – is comfortable.



Bottom line, we liked it so well this is what I installed in the new camper.



I hope those of you that are curious about this furnace find my installation and experience with using it helpful.

You and Julie did a beautiful job. Amazing work. I loved reading about it. Thank you for sharing.

 

[h2opup]

Wonderful write-up ski3pin. In addition to the install how-to, your description provides a lot of practical information on how these units work.

My new topper came with a Truma Vario installed on one wall. I'll be putting it through its paces on a first-camping trip to happen soon!

 

[bkel33]

Thanks for the writeup ski3pin.

I recently purchased a truma varioheat that was taken off a conversion van for my teardrop. I have it all installed, but cannot get it to turn on. My varioheat harness was cut and the connector is missing. I'm wondering if I have the pinouts/ wire colors connected correctly. I was searching the internet for pictures of the harness and after looking at pictures I have the green and orange connected to temp sensor and orange and white jumpered (window switch). Can you confirm if this is correct? What goes to the black and brown wire? The wires are white, orange, green, yellow, brown, black. Attached pic with harness in question.

 

[ski3pin]

First cell service in 3 days and do not have my tech information. I'm happy to do this for you on our return in a couple weeks.

 

[Sagebrush Reconnoiterer]

First cell service in 3 days and do not have my tech information. I'm happy to do this for you on our return in a couple weeks.

Amazing that there still is cell service, since the mine was mothballed in 2006. With that, I’ll let you two continue field researching for your next book …

 

[bkel33]

Thanks Ski3pin!

Does the white wiring box have wire terminations in it, or does it just serve as a housing for the connectors?

 

[ski3pin]

Just housing for the connections. There is a diagram on the lid.

 

[ski3pin]

But I see you already have that in your post above.

 

[h2opup]

Here is the schematic on my Truma Vario, and some other pics from my unit. Hoping that these might be helpful until ski3pins' return.