Diesel and gas heaters
Diesel ducted heating v gas ducted heating.
A topic which produces polar opposite viewpoints in any healthy campground discussion. Unfortunately opinions are often based on “my XYZ heater is the best for sure” which is usually supported simply on the basis that they themselves have XYZ heater, and not much else. As with all vested views no-one wants to admit they got the shit one.
I have a diesel heater, its been great to us and I love it but Ill try my best to stick to the facts. Ill also be sticking to only the brand named units Truma for gas and Eberspacher for diesel. You are of course welcome to take the punt on the cheap knock offs, but let me know how they are going after year or so.
The reason I have it a diesel heater, and why I chose the Eberspacher brand over thje other offerings including the cheap knockoffs is important. Many years ago we took our first full full bathrrom, full height van on a weekend soire with a large group of friends. The trip was to the middle of Victoria in the middle of a particularly cold Victorian winter. I was full of confidence because I “knew” that the rooftop aircon would heat the van adequately in any climate. I thought it would be particularly opulant to throw in a blow heater to make the bathrrom extra warm.
The weekend was very, very cold at night and the temperature dipped below zero quite early in the evening whilst the crowd of friends stood around a fire drum having a few cordials and a more than a few laughs.
Barb who had earlier returned to the van to cook dinner send our son to summon me urgently. The reverse cycle aircon in our new van had blown a valve, and blew up. That’s when I discovered to my absolute horror that reverse cycle aircons all have a temperature point where they can no longer function as a heater and in our particular case that was 3 degrees, which now it was zero that was 3 degrees ago.
Our van temperature plummeted and was it was now almost as cold inside as it was outside. We were partially saved by the little blow heater but in our large offroad van that blow heater struggled to keep the van at 16deg, but at least it was better than nothing.
One of the group with a virtually identical also new van had a diesel heater and he sung its praises loudly. I checked it out, gave it a thorough going over and was very very impressed to say the least. Their van was so hot inside I almost passed out and I was sure the chicken they were having for dinner had cooked itself sitting on the bench.
That was Friday night and by 9.05am on Monday morning I had ordered a diesel heater kit from a local supplier. There were cheap knockoffs around back then, but the unit I experienced and was star struck by was the Eberspacher Airtronic 2.2kW, so that is what I got and to be honest its repeatedly proved itself and performed flawlessly.
I had no idea if gas heaters were even around back then but Im certain that would not have effected my choice. With all the diesel and gas heater facts I have today, I’m still not sure I would choose gas over diesel but I believe gas is at least as good an alternative, and in some regards a better option.
Unit costs. With heater unit purchase costs, the ability to research and wheel and deel online the purchase price of a Truma or Eberspacher will likely end up somewhere around the similar price point. Sourcing the Eberspacher unit offshore particlualrly from the UK will provide huge savings for relatively little risk.
Installation. Diesel heater installation its mostly plug and play, doesn’t require any licensing or regulatory compliance, and the entire installation is well within the skillset of most handy people. Gas heater installation is different in that gas compliance is required so whilst the unit placement and duct work can be done by the handyman, at least some so 3rd party assistance is required for the gas works and that will attract a cost.
Outsourcing the entire heater installation of wither unit will of course add cost to the purchase price, and more so with the gas compliance required for the gas heater.
The diesel heater’s combustion intake and exhaust go vertically through the floor so the heater can be installed almost anywhere. The gas unit needs to be flued to an external wall. In addition regulations forbid installation of the flue near a window or door so that may or may not impact the preferred installation location; or may well make installation of a gas heater impossible.
Its important with the gas heater to confirm all gas plumbing and the instal location is compliant and signed off. I know from experience caravan service centres will use unqualified and unskilled staff to do gas plumbing work, which is not only illegal but potentially very dangerous
From an article written by industry supplier Everything Caravans, states that there are a selection of gas heaters on the market overseas which failed muster under Australian compliance which is said to be strict as a result of RV gas heater related deaths. The Truma gas heater is the only gas unit compliant with Aust gas regulations. With our countries generally slow and second rate safety record (Takata airbags for example) that info certainly doesn’t inspire with me with confidence.
Heater repairer Everything Caravans recommend the diesel heater to be a more robust when it comes to use in offroad vans, but I suspect that would mean hard core offroad
Running. Much like a house ducted heater, the gas heater when running is either on or off which is one of my personal dislikes; ie it comes on at maximum output until the preset is reach and then it switches off until the temperature drops by a predetermined amount, in the case of the Truma 2400 thats 4 degrees. That has been addressed in less than complete manner with the current model having a half output setting.
By comparison the diesel unit varies its output automatically dependent on demand. The diesel unit comes on at maximum output and reducing automatically to a silent low once it reaches the preset temperature. The diesel heater remains on low until its switched off, or the ambient temperature rises above the preset such as naturally with morning sunshine.
The diesel heater is fed diesel by a dose pump, which makes a ticking sound. The dose pump provides a constant and precise “dose” of fuel at each tick dependent on demand; ie the dose volume remains constant, but the frequency increases and decreases to match demand … and this is one of the favourite criticisms of diesel heaters. The dose pump audibly ticks each time it pumps a dose to the heater, much like a loudish clock. The pump can dose up to twice a second at maximum output, and down to every 2 seconds or so when the heater is on low ….. but it ticks, and it ticks, and it ticks, and it relentlessly ticks.
These are audio recordings of our diesel heater in various proximities and stages of operation. Aside from the dose pump in the quiet of night whilst in bed, you wont hear much of this action from inside the van … but the neighbours might
The diesel dose pump recorded under the van next to where the pump is mounted.
The air intake recorded close to the inlet under the van
The air intake with a piece of foam as a muffler recorded close to the inlet under the van
The heater operating at maximum output recorded 2 mtrs off to the side of the van (You’ll need the volume of both the computer and audio player on high to hear this one)
The heater operating at near minimum output recorded 2 mtrs off to the side of the van (You’ll need the volume of both the computer and audio player on high to hear this one)
The pump will likely be installed attached to the chassis under the floor, but if the pump is installed nearer the bed it may well drive you insane. I sleep like a corpse but Barb is a light sleeper. Our pump is under our bed and whilst I dont hear it, it took Barb some time to get over the ticking and early on she often turned the heater off during the night. Now we’re both oblivious to it … bit like living next to a train line, eventually you’ll be too tired to care
The fuel path for the diesel heater is tank, low pressure line to the pump, pump, high pressure line to the heater. The low pressure fuel line can be upto a maximum 2 mtrs from the fuel tank to the pump. The high pressure line can be upto 5 mtrs or so from pump to the heater. That means the fuel tank must be within 2 mtrs of the pump, so if the fuel tank is mounted around the draw bar the pump will need to be mounted under where the bed is located in most caravans. If the fuel tank is mounted at the rear of the van the pump can be positioned well away from the bed, down the back of the van.
In regards to the pump ticking sound, what you will barely hear during the day will sound like the Little Drummer Boy in the dead of night.
The gas heater has an exterior wall mounted flue, which is capped off when the heater is not in use. The heater cant be used unless the flue cap is removed and that may well have to form part of the list of usual camp set up practice, either that or you’ll be doing a 6am nudie run outside in 5 degrees to un-cap the flue, to be able to turn the heater on. The diesel heater has no such limitations and can be started anytime without other preparation.
The diesel unit has the ability to connect a programmable timer, a remote control and a phone-in module if you are particularly wierd or tech driven. The diesel heater is a true one button device, turn it on and leave it on, and it will work out for itself when to fire up and when to shut down … including whilst your towing if you wish
The operational differences between gas and diesel in theory means the diesel heater is always on and operating at a low output the diesel heater should ultimately be on average generally quieter, and be more likely to maintain a more consistent room temperature once its reached its preset temperature. The thermostat in the gas heater is set require a drop in temperature of 4 degrees before the gas heater will come back on which would be likely to produce a noticable temperature fluctuation, much like the reverse cycle aircon. The gas heater heats very well, and as the temperature fluctuation is only an actual cristism when the gas heater is compared it to an alternative that dosent doesnt fluctuate.
Fuel consumption. Maximum fuel consumption specs are the only fair and true spec based comparison, without running each of the heaters in identical vans together at the same time side by side. Real world usage wont see either of the heaters max out on fuel consumption for anywhere near 100% of the time. Both units reduce output and fuel consumption considerably once they reach their preset temperature. The diesel heater does it by progressively reducing output and the gas heater does it by cycling off and on. The 2.8kW gas heater uses 193grams of gas per hour during maximum output. The diesel heater consumes 280ml of diesel per hour during maximum output.
On coolish nights or just maintaining a temperate overnight comfortable sleeping temperature the heaters will only be running at their minimum outputs. With sub zero outside temperatures the heaters would be running harder and closer to a constant maximum output. The gas heater has two settings off, and cycling from nothing to 100% output. In contrast the diesel comes on at maximum output, then slowly and automatically over 30min or so reduces the output (along with power and fuel consumption) as it reaches the preset temperature. Reduced fuel usage with the diesel heater comes from reduced output at the preset temperature, fuel reductions with the gas come from the heater cycling off and on once its reach the preset temperature.
The gas heater is 2.8kW output, where as the appropriate caravan diesel unit is 2.2kW so based on specifications the diesel will on paper be generally working harder than the gas unit. Eberspacher have a 5kW unit but diesel heaters are required to regularly be run at a maximum output to reduce carbon buildup so dont be tempted to use a larger unit with the idea it will run less; it will run less, but it will also choke itself to death.
Over winter and the shoulder seasons where the days can be warm and sunny, but the nights get down to zero our diesel heater consumes on average around one litre of diesel per day. During those seasons when the heater is used most days we just leave the heater turned on all the time and let it do what it does best, silently keeping our van at the perfect temperature day and night. During the day as the sun warms the van the heater shuts itself down completely, automatically As soon as the sun goes down and the chill appears the heater automatically comes to life on low and silently maintains the preset temperature without any input from us.
In very cold weather, we’ll often leave the heater on over night on a reduced temperature just to take the chill out of the air. On low a diesel heater is abolutely silent.
Using the table below enter the current fuel prices to get an indicative cost comparison using the maximum output costs of each unit.
Power consumption. Both units being 12v means they are both exceptional must haves for off grid freecamping, and fortunately both units have relatively low 12v power consumption. The gas unit a minimum 0.80 amps, and the diesel 0.40 amps.
Gas heaters are completely maintenance free, but diesel heaters require a recommended annual or biannual service. Gas heaters burn clean where diesel heaters produce carbon in the burning of the diesel. We service our diesel heater every 2 years, but its a process that requires some knowledge and some down and dirty hands on participation. If your not handy then the choice of a diesel heater would include taking the van to a service agent for the heater service, which adds inconvenience and cost. I have heard people paying upto $500 for a service, albeit that would surely have to include unit removal and some replacement parts.
The diesel heater builds up carbon deposits that left unattended will cause running issues including significant smoking on start up. Smoking is usually the tell tail sign of carbon … which from experience may cause passers by to panic and try to force evacuate what they believe to be a burning caravan.
This is our heater smoking during start up after I decided to push the service interval out a little to far. With early intervention, no damage is caused by carbon build up it just provides more of an embarassing side show for onlookers.
Carbon buildup will cause inefficiency which will causes more carbon, and ignored that will lead to damage to the heater. Two things you’ll notice in the video below is terrific but unintended background music (that YouTube accused me of a 21 sec copywrite breach) and more importantly the obvious point near the end of the video where the significant smoking abruptly stops, this is where the heater finishes the start up phase. The glow plug goes out and the heater fires up to its normal full running condition. This is a typical carbon-ed plug screen.
The remedy for this is the simply 15min service to remove, clean and replace the plug screen from the in-situ heater, and that requires no parts replacement.
A diesel heater needs to be run on maximum output regularly to help clean it out and reduce carbon buildup. Its important to avoiding running the heater on a low settings for long periods, and thats why its not advisable to buy a bigger heater which will generally run lower. A diesel heater should not be run for short periods either, as this will increase the potential for carbon deposits.
Periodic maintenance is vital for ongoing diesel heater efficiency. The key elements of a diesel heater service are to clean or replace the glow plug, and glow plug screen to remove any carbon deposits. The fuel filter should also be replaced, and fuel and exhaust lines checked.
The cheapest hands on service is the minimum replacement of at least one gasket at $20. The potential for service parts can be as high $300
A glow plug and glow plug screen check is relatively easy and free of parts of replacement parts. This minimum service can be done with the heater in-situ so long as its accessible. Anything more than the glow plug check will require the entire heater to be removed, dismantled, cleaned, checked and at least some parts replaced. None of this will ever be required for a gas heater
Opinions, myths and campfire stories
A gas bottle will last longer for the gas heater than a standard 10ltr diesel tank, but you can of course simply get a bigger diesel tank.
You cant get a cup of gas from a fellow camper to keep you warm for the night in you run out of fuel …. but who would every wander the campground asking other campers for a cup of diesel for their heater? We often carry a 20ltr jerry for the car anyway but we always have one litre bottle of diesel tucked away which allows us a day of heating before we need to pop down to the petrol station. If we need more than our 10ltr tank of diesel, lets face it, the camp area is probably too cold to enjoy the place anyway, so we’ll leave
Diesels heaters stink. A well maintained diesel heater does not smell at all
Diesel heaters are noisy. The noise most people hear is the air intake which can be noisy, but its only noisy on maximum output. Mufflers are available and make a significant difference, and like us make a muffler can be made with some plumbing pipe and some foam.
You’ll run out of the gas too quickly because you already use your gas for cooking, fridge and hot water. A gas heater will consume around 5 times that of a 220ltr fridge, so a full bottle (which most vans have two) would last at least a week running 10 hours per day.
Vans carry gas already, and I don’t want carry a second fuel (diesel) for a heater. Most tow vehicles are diesel so your carrying the second fuel anyway. I can assure you its far easy for us to top up our diesel heater tank when filling the car, whether our car is diesel or petrol, than it is to source and swap out a gas bottle which youll only want to do when its empty.
A key point is diesel in our heater tank is only ever “topped up”, yet a gas bottle is always drained dry and only then will it be filled or swapped. Heading to a freecamp with quarter full diesel heater tank, I simply top up the tank on the way. What are you going to do, and how are you going to get around that quarter full gas tank ???
Diesel heater pumps annoyingly tick and drive you mad. Yes they do 🙂
Gas costs a small fortune in remote Australia. Yes it does
In summary both heater worked incredibly well. At city prices the fuel costs are close enough. The decision will generally come down to maintence inconvenience/costs and