How I keep my trailer warm in subzero temperatures with Chinese diesel heaters.

[Bobert]

My experience with Chinese diesel heaters is one of trial and error mixed with educated guesswork. I wanted to be able to keep my 38’ travel trailer warm a -30 degrees Fahrenheit. Since I rebuilt the trailer with this in mind I insulated the walls and ceiling at r10 and the floor at r14 using polyiso insulation. This compares to the theoretical r3.5 the trailer came with. I chose to use diesel heaters primarily because the lp furnace we used on our other similar size camper could not keep up with the cold once the temperatures dipped into the teens mostly because the tanks would get cold and not supply enough propane to the furnace. Secondly the diesel heaters are small enough to fit in the limited space we had available. Third since at least two diesel heaters are required to meet the heat demands of the size of my travel trailer at -30 and one will work down to 10 degrees the redundancy of two heaters is helpful as only one will be absolutely needed for most of the heating season in addition the lp furnace is still available in an emergency. Fourth the electrical power consumption of the diesel heater is considerably less than the lp furnace.

Our definition of comfortable is temperatures in the upper 60s with usable hot and cold water.

The first thing was to figure out how much heat I would need to supply the trailer. Time for google.

A quick check of a btu calculator shows a minimum requirement of 42000 btu to accomplish this feat.

Unfortunately each heater maxes out at a 5.5k heat input. That’s about 18,000 btu per heater 36,000 btu total. Obviously no heater is 100 percent efficient so I won’t actually get 36000 btu of heat. Fortunately the calculator that I used is designed for calculating the installation of a wood burning stove so I can assume that the actual btu output required for my space is closer to 34000 btu. That’s close enough for me to go ahead with the experiment. I installed 2 5k diesel heaters and before I insulated the floor I ran 300’ of 3/8 pex pipe throughout the floor to see if I could capture the lost heat from the exhaust and return it to the floor to keep the tanks from freezing and make the floor warm. I installed the heaters. I found that into the teens a single heater was sufficient but at that temperature two heaters actually used less fuel apparently the efficiency of these heaters drops the hotter they are fired. So I figured I had close to enough btu output to keep the trailer “warm” at -30 but how am I going to keep my water tanks and pipes from freezing below the floor. My idea is to use exhaust heat recovery to pipe warmed water throughout the floor and around the holding tanks. According to you tube channel “David Mcluckie “ he has concluded by experiment that a coolant heat recovery system can extract between 500 to 800 k of heat. That’s potentially more than a conventional electric space heater at almost 5500 btu. I used 2 egr coolers originally designed for the 6.0 liter ford powestroke engine as my heat exchangers and a small 12v hot water pump attached to a overflow tank in order to circulate the coolant through the 3/8 pipe I had previously installed. The installation was full of challenges but the end result was that I was able to keep the inside of the camper at 64 degrees at -31. We can live with that.

 

[Bobert]

I intended to give additional information about my trailer before posting so rather than editing the post I will add it post script

I use a 3500w 48v all in one solar inverter and 4 lifepo4 100ah batteries in series inside the trailer. Our travel trailer is 38’ (the cabin itself is 35’) it was built in 2000. In order to use my solar setup I need to be able to keep the equipment above freezing and to winter camp I need to do a whole lot better than that thus the grand experiment with diesel heaters.

 

[Bob B]

Any idea how much diesel you use per day when running them both?

 

[Bobert]

Any idea how much diesel you use per day when running them both?

I haven’t done an actual audit yet. In the 30 below weather I was using about 10 gallons every 2 or 3 days I have two 5 gallon cans and In subzero weather it’s kids risky if I go 3 days but if I go every 2 days I have to empty a gallon or 2 out of the cans (usually into a rocket heater I use for other things) in order to fill empty cans. I am presently using kerosene instead of diesel because the diesel begins to get thicker as it get colder and can cause the heaters to shut down. As temperatures rise the consumption of fuel drops dramatically. Last night I got new cans of fuel and my consumption was about 2 gallons in 22 hours but that is with temperatures at about 20 degrees and hitting 40 just a little while ago. I had to shut off one of the heaters because it was 77 inside with both on their lowest setting. For the next few hours I will not use hardly anything. If I calculate what I should need for btu output and the btu per gallon of kerosene I think I am approaching %90 efficiency.

 

[12VoltInstalls]

I used ~$110 propane for December but that was before storm window panels. 16000btu RV furnace, 3A basically continuously. Only had 28F below once; you had 30 below Fahrenheit or Celsiusly?

I’m trying to guess - compare to my situation

 

[Bobert]

I used ~$110 propane for December but that was before storm window panels. 16000btu RV furnace, 3A basically continuously. Only had 28F below once; you had 30 below Fahrenheit or Celsiusly?

I’m trying to guess - compare to my situation

Fahrenheit is the temperature I used in my post. My travel trailer has a 35’ cabin with 2 slides so my total area is about 330 square feet.

 

[Bugwubber]

good write up! I have two as well but have only installed one to date in my mh. I put it under the dash since the front was the coldest spot. These things are awesome, just keep spare parts on hand! i got the “8kw” heaters (which aren’t if you didn’t know). The second one I want to patch into the propane heater ducting so if can act like a half power furnace. That will take some extra trickery to add dampers etc.

have already replaced a glow plug so figure that’s something to stock.

 

[Bobert]

I used ~$110 propane for December but that was before storm window panels. 16000btu RV furnace, 3A basically continuously. Only had 28F below once; you had 30 below Fahrenheit or Celsiusly?

I’m trying to guess - compare to my situation

Fahrenheit is the temperature I used in my post. My travel trailer has a 35’ cabin with 2 slides so my total is about 330 square feet.

good write up! I have two as well but have only installed one to date in my mh. I put it under the dash since the front was the coldest spot. These things are awesome, just keep spare parts on hand! i got the “8kw” heaters (which aren’t if you didn’t know). The second one I want to patch into the propane heater ducting so if can act like a half power furnace. That will take some extra trickery to add dampers etc.

have already replaced a glow plug so figure that’s something to stock.

yes I have replaced 1 glow plug but it was a factory defect. I have replaced 2 fuel pumps I think both of them failed because they were run for a while in the horizontal position one of the drawbacks of an experimental setup it has been easy to knock them off their mounts and not notice. I ruined a heater by having the power cut to it while it was at full heat.
I have had 3 challenges with my installation that I did not anticipate. 1. The fuel (even winter fuel) gets to thick for the heater to work even when the temperature at only slightly below 0. I bent the fuel line so that I can feed the fuel from a heated space.
2. The wooden floor gets to hot from the exhaust. I ended up welding two 4 and 11/16 electrical boxes on top of each other and welded a short length of 1 1/4 conduit in a hole I drilled through the two boxes in such a way that the incoming air cool’s the exhaust pipe so that the outside of the box is cool to the touch. Kind of hard to describe but it solves the problem.
3. They tend to coke up when used on idle for to long. I switched to kerosene and that seems to have solved the problem and it also keeps the egr coolers clean.

 

[100 Proof]

Questions for you:

• What is the BTU/h or kW rating of your propane furnace?
• Is it sufficient to carry your trailer at -30?
• If so, is it cycling or running full time?

Some things to keep in mind:

• The diesel fuel heaters run constantly, while most propane furnaces cycle on/off at full power.
• 36,000 BTU at 100% duty cycle is equivalent to 42,000 BTU at 85% duty cycle.
• A 5kW diesel fuel heater can indeed produce an honest 5kW of heat.
• You can add anti-gelling agents to diesel fuel.

 

[Bugwubber]

Fahrenheit is the temperature I used in my post. My travel trailer has a 35’ cabin with 2 slides so my total is about 330 square feet.

yes I have replaced 1 glow plug but it was a factory defect. I have replaced 2 fuel pumps I think both of them failed because they were run for a while in the horizontal position one of the drawbacks of an experimental setup it has been easy to knock them off their mounts and not notice. I ruined a heater by having the power cut to it while it was at full heat.
I have had 3 challenges with my installation that I did not anticipate. 1. The fuel (even winter fuel) gets to thick for the heater to work even when the temperature at only slightly below 0. I bent the fuel line so that I can feed the fuel from a heated space.
2. The wooden floor gets to hot from the exhaust. I ended up welding two 4 and 11/16 electrical boxes on top of each other and welded a short length of 1 1/4 conduit in a hole I drilled through the two boxes in such a way that the incoming air cool’s the exhaust pipe so that the outside of the box is cool to the touch. Kind of hard to describe but it solves the problem.
3. They tend to coke up when used on idle for to long. I switched to kerosene and that seems to have solved the problem and it also keeps the egr coolers clean.

YES mine gelled too. Will definitely try out antigel.

We always run the heater on high for 5min before shutdown. So far so good on that.

I wonder if a booster fan would help optimize the duct temp

 

[Bob B]

I have read that kerosene doesn't have enough lubricant qualities and can cause fuel pumps to go bad .... I don't have one of these, so that's not first hand knowledge.

I do have a diesel truck and anti gel treatments are pretty standard for the winter to prevent gel problems.
Around here, once you reach a certain date the treatment is included when you pump the fuel.... I always add some extra each tank in the winter time anyway and have never had a problem.
They manage to run a lot of diesel engines up in the arctic where it may be -60F.

 

[Bobert]

Questions for you:

• What is the BTU/h or kW rating of your propane furnace?
• Is it sufficient to carry your trailer at -30?
• If so, is it cycling or running full time?

Some things to keep in mind:

• The diesel fuel heaters run constantly, while most propane furnaces cycle on/off at full power.
• 36,000 BTU at 100% duty cycle is equivalent to 42,000 BTU at 85% duty cycle.
• A 5kW diesel fuel heater can indeed produce an honest 5kW of heat.
• You can add anti-gelling agents to diesel fuel.

My trailer has a 38000 btu furnace it is not presently running because it developed an internal gas leak. So I can’t check it’s performance against the diesel heaters. The lp furnace simply will not work at -31 unless you have a large or heated tank. We have another 38’ trailer that we have used that has the identical furnace. And a few years ago my wife and I stayed in it for a few nights to free up our house for guests. We hit 10 above for a low one night and we were ok because we new the furnace wouldn’t work properly at that temperature with our 20 pound tanks so we had tons of blankets. I don’t think it was much above 40 in there overnight. Yet the same trailer was easy to keep at 70 with a mid 20s outside temperature. The problem was that the output temperature of the furnace would gradually get colder until the furnace was blowing lukewarm air. Of course under those conditions the furnace ran continuously. Trailers tend to not have much thermal mass and a On off furnace will tend to cycle quite frequently even at relatively warm temperatures.

The trailer furnace is rated at input btu and the efficiency is estimated to be be between 60 and 70 percent. I doubt I could keep a 60 degree inside temperature at -10 much less -31.

My trouble wasn’t the fuel gelling I was using winter diesel the issue was the viscosity of the fuel was getting thicker. It is my understanding that the anti-gel additives can contribute to the “coaling up of the burn chamber” and I wanted to avoid that possibility while I am still experimenting with the egr coolers.

The biggest benefit is my ability to keep the holding tanks above freezing at such cold temperatures.

 

[12VoltInstalls]

lp furnace simply will not work at -31 unless you have a large or heated tank. We have another 38’ trailer that we have used that has the identical furnace. And a few years ago my wife and I stayed in it for a few nights to free up our house for guests. We hit 10 above for a low one night and we were ok because we new the furnace wouldn’t work properly at that temperature with our 20 pound tanks so we had tons of blankets

I have a 25’ with a 16K BTUs propane furnace that kept 65*F overnight with -28*F so I’m not hearing that
It was 15F this morning and 68F when I got up before sunrise.

 

[Bobert]

I have read that kerosene doesn't have enough lubricant qualities and can cause fuel pumps to go bad .... I don't have one of these, so that's not first hand knowledge.

I do have a diesel truck and anti gel treatments are pretty standard for the winter to prevent gel problems.
Around here, once you reach a certain date the treatment is included when you pump the fuel.... I always add some extra each tank in the winter time anyway and have never had a problem.
They manage to run a lot of diesel engines up in the arctic where it may be -60F.

I have heard that to but I have not been able to find anyone with a failure attributed only to that issue. I have heard of others who have switched and not had any trouble. So I going to find out for myself if that is true or not. Fuel pumps are cheap enough and easy to change.

 

[Bobert]

I have a 25’ with a 16K BTUs propane furnace that kept 65*F overnight with -28*F so I’m not hearing that
It was 15F this morning and 68F when I got up before sunrise.

Yes 16000 btu probably won’t have that same problem. I’m using double the propane and cooing the tanks really fast. Do you have any slides? I have 2 on an older trailer and no skirting of any kind.

 

[Bobert]

good write up! I have two as well but have only installed one to date in my mh. I put it under the dash since the front was the coldest spot. These things are awesome, just keep spare parts on hand! i got the “8kw” heaters (which aren’t if you didn’t know). The second one I want to patch into the propane heater ducting so if can act like a half power furnace. That will take some extra trickery to add dampers etc.

have already replaced a glow plug so figure that’s something to stock.

The problem with using the existing ductwork is if it is not insulated well you will loose much of your heat though the ducting. If you leave the lp furnace in place you will also loose heat through the exhaust and air intake vents.
Know one seems to know why sellers refer to them as 8k heaters as experiments have shown that it is physically impossible for a input of 8k of fuel to be fed into them in stock configuration much less an output of 8k.

 

[12VoltInstalls]

problem with using the existing ductwork is if it is not insulated well you will loose much of your heat though the ducting.

Losing heat into the space you’re heating? Is a problem?

 

[curiouscarbon]

Losing heat into the space you’re heating? Is a problem?

perhaps they mean to say that the heat will conduct outward via the vehicle envelope directly through the heated ductwork to frame, e.g. every BTU delivered to exterior shell is "wasted" relative to delivered via ductwork into living space. i am guessing, apologies if this is in error.

 

[Bobert]

Losing heat into the space you’re heating? Is a problem?

It depends on how your rv is made. The default on travel trailers the age of mine is to have a poorly sealed duct with 1 1/2” of fiberglass compressed to 1/2” against it and a tarp material separating it from the outside world. Lots of heat loss. Some of the motorhomes have much better insulation in the floor

 

[12VoltInstalls]

depends on how your rv is made.

Ahh. Myopia I had.

The ductwork in mine is interior, running under the cabinets on the floor and keeping the plumbing warm. Warmish. There’s 3-1/2 whole inches of insulation in my floors.
My prior camper was this same brand and series but a 4’ shorter model and NO insulation in the floors. Still ducted the same.
The current one is significantly warmer from the knees down. And any heat lost from the ductwork is still contributed as heat.