Autumn is upon us and at this time of year an RVers thoughts turn to winter touring – that’s if it ever stops raining, floods subside and roads reopen. Heating your RV is an important consideration because it adds more than just utility (by allowing year-round travel), it adds enjoyment and comfort. It also means there is less likelihood of mould and mildew – important considerations for both health and maintenance.
In an effort to keep prices down, ducted heating is usually offered as an optional extra in new RVs. Consequently there is a healthy after-market industry supplying and fitting ducted heaters as add-ons to existing vans.
If you are thinking about installing a heater, what are your options? Without including mains power, there are two types of ducted heaters available: those fuelled by LPG and those fuelled by diesel. The technology driving modern LPG and diesel heaters has become quite sophisticated and both options are reliable, safe and fuel efficient. So, which do you choose?
Heating Pros and Cons
We had a diesel heater retro-fitted in our (diesel-powered) van a couple of years ago and it is excellent. Friends have an LPG heater installed in their slide-on camper and they are equally happy with its performance. Neither heater has experienced any maintenance or reliability issues. Just press the on-button, set the temperature and away you go: The living area is warmed within minutes.
After browsing manufacturer’s sites and discussing experiences with other campervan and motorhome owners, there appear to be just a few measures that differentiate between LPG and diesel-fuelled heaters.
- Modern diesel heaters are microprocessor-controlled, providing ‘step-less’ incremental adjustments to the heat output when left running overnight. Once the living area is up to temperature the heater and fan taper off, ‘trickling’ on only when required to maintain the set temperature. You barely know the heater is running.
- LPG heaters have traditionally functioned in a more binary fashion, using a thermostat to switch the heater and fan either fully-on or off as the cabin temperature varies. However, recent models (e.g. Truma VarioHeat) have a very quiet night mode.
- Diesel heater exhausts are audible from outside the van, particularly when starting up. Once the cabin is up to temperature and the heater has tapered off, external noise output from the heater is negligible.
- LPG heater units are quiet outside, the only noise being from the internal fan.
- An LPG heater requires an external flue in the wall adjacent to the heater, as opposed to a diesel heater’s exhaust pipe, which is more easily fitted under the floor. There are regulations regarding the location of an LPG heater flue in relation to windows, doors and other LPG appliances, so that toxic exhaust gases aren’t able to be drawn into the living area.
- LPG burns less efficiently at high altitudes. This can be an annoying issue with hot water heaters and while it is also likely to be an issue with ducted heaters, it might be less noticeable (diesel heaters operate efficiently up to 1500 m).
- In a compact campervan or motorhome, one ducted outlet will warm the living space within a few minutes. Larger vehicles with higher capacity heaters can have multiple outlets – living area, dining area, sleeping area and even an outlet in the bathroom (ideal for drying towels and wet clothing and footwear).
- A diesel heater can also be running while driving, so the living area is cozy and warm when you stop. This is particularly useful in a large vehicle in very cold weather, especially as the cab heater from the engine will struggle to keep the cab warm, with so much air escaping into the cold living area. It’s also great if carrying passengers at the dinette.
- Some comparison websites report that LPG heaters deliver a ‘damp’ heat, causing humidity and condensation. I don’t believe this to be the case with ducted RV heaters that deliver their warmth from a heat exchanger. I expect any moisture resulting from the LPG combustion process would be expelled through the flue with other exhaust. Most likely, such reports relate to un-ducted heaters, which are a real no-no.
Heat Exchange - All Hot air!
Both LPG and diesel heaters use a heat exchange process to duct warm air to the living area of your campervan or motorhome.
Fuel (LPG or diesel) is burned in a combustion chamber, heating the walls of the chamber. Air is blown over the hot outside walls of the chamber (fabricated with fins to increase the surface area and better dissipate heat), the resulting warm air being transferred into the vehicle via flexible ducting.
The combustion chamber where the fuel is burned is completely separate from the compartment where the hot air is sourced, so no fumes from the burning fuel enter the vehicle. The combustion chamber’s air is drawn from outside the vehicle, and of course the exhaust from the combustion process is released outside the vehicle.
Fuel Type – Diesel
If your RV has a diesel engine then a diesel-fuelled ducted heater is the obvious option. In modern diesel vehicles, the heater must be connected into the fuel tank to access fuel, with the pick-up pipe set 25 mm above the bottom to ensure it can never use all fuel. Never just tap into the fuel line because the fuel system of modern, common-rail diesel engines is pressurised and doing so can cause major engine issues. Alternatively, connect the heater to a separate diesel fuel tank, which is also the solution for a slide-on camper, fifth-wheeler, caravan or camper trailer.
- Diesel heaters use only a small amount of fuel, perhaps little more than a litre or so if left running all night.
- The heater does not deplete the on-board LPG supply used for cooking and hot water.
- The heater uses a small amount of 12V electricity to heat the glow pin when starting up and also to power the fan and control unit.
- Fitting a pick-up in a vehicle’s tank to draw fuel requires some specialist expertise, knowledge and experience. This is not a DIY project!
Fuel Type – LPG
If your vehicle is petrol-powered and you already have LPG for other appliances, an LPG-fuelled ducted heater is the go-to option (at least if you don’t want a diesel heater connected to its own fuel tank). An LPG heater can be connected into the existing gas plumbing.
- There is no need to carry an additional fuel source as the heater uses the same LPG supply as your cooking and hot water appliances.
- LPG is widely available at filling stations and exchange outlets at service stations, hardware stores and outdoors stores.
- Connecting your heater to existing LPG lines is usually a relatively straightforward job for a qualified gas fitter, depending on the location of the heater. Note, however, that installation certification is mandatory.
- An LPG heater requires an exhaust flue fitted in the wall or roof.
The heater uses a small amount of 12V electricity to ignite the gas and to power the fan and control unit.
Safety Considerations
Though widely used and generally safe in modern installations, LPG has inherent risks via potential leaks, flammability and toxic exhaust gases.
You don’t want to be exposed to exhaust gases from either diesel or LPG heaters, so the heater exhaust/flue should be located away from living areas and windows. LPG exhaust – carbon monoxide – is odourless and deadly. Strict regulations define the safe location of an LPG heater flue in relation to windows, doors and other air intakes for a motorhome. This often determines the installation location of an LPG heater in the van.
Important:Under no circumstances operate an LPG heater that uses an open flame to provide warmth in a campervan or motorhome. This includes using an LPG stove as a heater (an LPG stove should only be used for cooking inside a van, with adequate ventilation)! When LPG combusts it produces carbon monoxide, which is odourless and deadly.
Other Considerations
Uninterrupted internal air circulation in the van is required for ambient air to be drawn into the heater intake and warm air to be moved around the van. Don’t store equipment in a way that blocks or covers ventilation grills that feed air to the heater, which is usually installed in a cupboard or under the bed. Other points to consider are:
- Diesel is more readily available than LPG in remote areas. This could be an important consideration if free-camping for extended periods of time in these areas.
- Brand-name diesel heaters (e.g. Eberspacher and Webasto) cost a few hundred dollars more than similar quality LPG heaters. ($2100 v $1800 approx).
- Combined hot water and air heaters (e.g. Truma Combi) are available for saving space in smaller vans, although the water tank capacity is only 10-litres. Cost is around $2500 for LPG/240V or $3000 for diesel.
- Some heater comparison sites suggest that LPG heaters may not function correctly when the temperature drops below 2°C, due to the butane content of LPG. However, Australian LPG for non-car usage is 100% Propane, rather than a mixture of Propane and Butane as in other countries. This should provide for satisfactory combustion of LPG at low temperatures.
- Diesel heaters may require periodic maintenance, such as cleaning or replacing the glow pin, removing carbon deposits from the combustion chamber and checking the fuel filter. Hint: running the heater at full heat for an hour or so should clean any carbon deposits.
Cheap Chinese Diesel Heaters?
Cheap ‘copy’ diesel heaters are available on eBay for under $200. I have no first-hand experience with these units, although I expect they are cheap for a reason!
Browsing through the online support sites and YouTube videos related to these heaters, it seems that there are plenty of happy DIY customers, although these folk appear to accept what I consider to be the shortcomings of these units as ‘normal’. For example, one enthusiastic Australian YouTuber wasn’t concerned that the unit he bought didn’t include an exhaust tube, or an exhaust muffler, and that the fuel filter leaked. He was happy to rectify these issues as part of the DIY installation process. So, here is my take on cheap diesel ‘copy’ heaters:
- The heaters do seem to work, once various installation issues are resolved.
- The large number of contributors to online support sites for these devices is an indication of the number of installation and maintenance issues faced by owners.
- Reliability, parts availability, ongoing safety and general quality appear to be critical issues. Online forums suggest replacement parts are difficult, if not impossible, to obtain.
- Some owners report that the fuel pumps and exhausts on these heaters are noisy, but describe this noise as acceptable.
- I have read reports from repair workshops citing evidence of inferior quality materials being used in the manufacture of combustion chambers, resulting in the chamber walls and seals deteriorating over time, potentially allowing noxious gases to leak and mix with the warm air ducted to the living area. Worryingly, this deterioration is only discovered when the heater is being examined in relation to other issues. The owners aren’t aware of the fume leakage.
- With the above long-term maintenance issues in mind, some owners seem content to replace a cheap heater every couple of years if required and still consider themselves to be in front, based on the purchase price.
- I would suggest that if your van is worth somewhere between $25,000 and $250,000, it is a false economy to skimp on a cheap diesel heater in return for ongoing maintenance issues and potential safety risks.
The Bottom Line
The type of ducted heater you choose ultimately comes down to personal preferences, usually determined by the available fuel source.
- If your campervan or motorhome is diesel-powered, go with a diesel heater.
- If your vehicle isn’t diesel powered and you already have an LPG installation, go with an LPG heater.
- Both diesel and LPG ducted air heaters will keep you cozy and warm in cold weather and help keep your RV’s interior healthier and more hygienic be reducing mould and mildew, and helping to dry wet towels, clothes and footwear.
- Unless you have appropriate trade skills, have the heater professionally installed, especially the diesel fuel tank connection. And remember, any new LPG installation has to be officially certified.
- A cheap ‘copy’ diesel heater is likely to cause you grief in the long run.
More information and links to related web pages and discussions is available at compactrv.net