Installing an Eberspacher Diesel Heater

The following article is written by a customer. It discusses the comparisons he made when deciding what brand of diesel heater to buy and the extra installation steps he took to fit the heater in his particular vehicle.

His old Suburban LPG air heater was removed and the new diesel heater fitted into the same compartment. Due to restrictions below the floor line, the heater mounting plate was raised off the floor using custom made brackets. Usually the heater’s mounting plate is installed into the vehicle floor. For anyone interested, here’s a copy of the installation manual.

Disclaimer: The comments and opinions in this article don’t necessarily reflect the views of RV World or Eberspacher. You should conduct your own research and not make decisions based entirely on what is printed here. It’s recommended that any installer first consider the installation in depth, before picking up tools and beginning the project.

Time to replace my old inefficient heater, which brand diesel heater is best?

The 20 year old Suburban LPG heater in my American RV uses old technology and has a massive current draw of around 11 amps. Unfortunately during winter, it's almost impossible to recharge the battery system using solar power, so prudent use of 12v storage capacity was absolute necessity when freedom camping. I decided to replace my old heater with a modern diesel fuelled model. The advantage is that they are really quiet, small and more importantly, very power efficient. The only disadvantage is that they are expensive.

In NZ there are two worthy diesel heater choices and both are German made; the Eberspacher and the Webasto. There are also two cheaper diesel heaters brands, more commonly sold in Australia. The Snugger which made in China and the Yeki made in Korea. Both these cheaper units are copies of the market leaders and owner feedback suggests that they should be ignored. The most common complaint is that they’re noisy, unreliable and have a service life of only 2,000 hours compared to the market leader at 5,000 hours. Some marine users report only getting 1,500 hours from the Chinese heater.

Just comparing the two German units, I consider the Eberspacher to have the upper hand. The heating capacity, fuel consumption and power consumption of both brands is similar (although the Eberspacher is slightly more favourable). After doing considerable research, it seems the Webasto isn't as easy to service and the blower motor design life is shorter at 3,000 hours against the Eberspacher at 5,000 hours. Carbon build up in diesel heaters can be a problem and Eberspacher have thought of a solution. They run their glow plug at the beginning and end of each run cycle to ensure the combustion chamber is cleared of any excess fuel and carbon. A small amount of smoke is produced during this burn off, but it’s barely noticeable. The burner plate on the Eberspacher is larger, which means it's easier to maintain cleanliness. The Eberspacher kit comes with a spark arrester/muffler and a fuel filter (inside the pump), something the Webasto fails to do on both counts.

The D4 kit comes with 2m of black 75mm ID ducting which is used to bring cool cabin air to the heater (for heating) and then it ducts the warm air back into the cabin. On this particular installation, the vehicle already had existing warm air floor vents ducted throughout the RV. An aluminium plate was made up to block off the rear duct and act as a warm air input point from the diesel heater. Two layers of heat proof cloth were used to insulate the surrounding structure from the warm ducting and also make a snug fit. The cool cabin air (that is yet to be heated) is drawn through an existing vent into the locker cavity so I have left the furnace inlet air vent open and just fitted on the inlet guard.

As you would expect with anything German made, quality is obvious with every part that comes with this unit. They have thought of most things and you won't need to buy much at all to complete the installation. The kit even came with a diesel pick up point to install into your fuel tank.

Our RV also has a diesel generator. Its fuel is supplied by a flexible fuel hose which runs from the vehicle’s diesel tank. I decided to tap into this diesel supply. There are usually two pipes; one supplies fresh diesel from the tank and the other takes unused diesel back to the tank. Don't access the return line as typically it contains air bubbles, a by-product of the injector pump process. The bubbles will cause all sorts of problems for your new diesel heater. Once I determined which one was the supply, I 'clamped' the rubber fuel supply line with some vice grips to prevent fuel from leaking after you cut into the pipe. I used an old piece of inner tube to line the jaws of the vice grips so it didn't distort or puncture the fuel line. Next I installed a brass “tee” (not supplied) into the existing diesel fuel line. I ran the black plastic fuel line supplied in the kit from the T, making sure I crimped & fastened the pipe clamps well to ensure a secure connection.

Even though diesel doesn't readily ignite, be thorough and careful with the fuel line because it will remain that way for many years to come! Consider shielding the fuel pipe at every corner - especially when it comes in contact with the chassis. Old inner rubber tube, or even garden hose pipe can make ideal protection in these circumstances, as seen in the pictures below.

The fuel dosing pump is mounted inline between the fuel source and the heater. It comes with a special rubber holder which dampens the pump noise. It is very important that the fuel pump sits at a 15-30 degree horizontal incline. Eberspacher note this is so any air bubbles can naturally feed from the fuel pump to the heater and not become a source of a fuel blockage.

While the plastic fuel pipe can withstand a little heat, if it touches the hot exhaust pipe it can shrink and the fuel flow is restricted. It’s reported that it is almost impossible to see from the outside so is difficult to diagnose. Make sure the fuel hose is supported and kept away from the exhaust.

The heater comes with rubber cushion and floor mounting plate which bolts to the underside of the furnace. It was not possible to fit the mounting plate into the compartment floor due to restrictions below so I made some support legs to raise the mounting plate. 30mm wide strips of aluminium plate were used and holes drilled at each ends of the plate for mounting to the D4 and securing it to the floor. When using aluminium, always try and make any bends gradual, rather than say at sharp right angles, even though it might take a little longer to construct. Aluminium is quite a soft metal and has a tendency to lose some of its strength, if the bend is severe. Bending the aluminium around a pipe achieves a nice gradual curve and minimises any reduction in strength at the point of the curve.

A gloss black spray paint was used to paint all new aluminium fabrications and parts. I used paint able to withstand up to 500C temperatures but this was not really necessary.

Before fixing the heater in its final position, I spent some time considering the mounting location for the electrical wiring loom and the pipes that enter and leave the furnace. The combustion exhaust will reach temperatures of up to 230 degrees C so you need to be conscious of the heat that will be reflected from it, or transfer to any fitting which hold it.

The spark arrester/muffler is made from stainless steel plate and is folded into its finished shape before being spot-welded. This construction ensures it has an extended lifespan, however, it’s not completely airtight. Some CO2 / exhaust gas can leak; therefore it should not be mounted in the furnace cavity, but rather in an area external to the cabin.

On this installation a 30mm hole was cut in the cavity floor. This allowed the exhaust pipe to be wrapped in heatproof cloth for about 50mm as it passed through the floor area.

There was a 75-100mm wide open cavity below the floor that led to the outside of the RV. I used this to pass the exhaust pipe downwards to the muffler location. From here the remaining exhaust pipe took the fumes clear of the RV. The supplied 2m length of stainless steel pipe was more than enough to do the job.

The original heater exhaust exit point was blocked up and I only used the inlet air entry. By painting the pipe with black spray paint, the internal pipework is almost invisible when looking at it from the outside. The furnace cavity wiring was easy to do. The main wiring loom (A.K.A wiring harness) was prewired with special connectors so the wall controller, fuel dosing pump and heater just clip in.

The only significant wiring I had to do was bring in a 12V supply from the battery. Although the heater uses minimal power while operating, it does draw around 10A for approx 30-60 seconds during the start up and shutdown period – this is to heat the glow pin to approx 1200 degrees C in order to ignite the diesel on start up, or burn off any combustion residue before shutdown. It’s important that the supply wiring from the battery is large enough so there isn’t a big voltage drop while the glow pin is on. I used 6mm cable. The recommended cable size is 4mm for cable runs up to 5m or 6mm for from 5m-8m.

Installing the electronic wall controller inside the RV was next. I mounted it in the kitchen on the fridge wall cabinet. It’s easy to see and access being in the middle of the RV. The supplied 8m loom wasn’t long enough so it was cut and extended to reach the display unit location. The electrical loom that comes with the D4 has plug connections on either end, so passing these plugs and sockets through wall cavities is not easy. Cutting the electrically colour coded cable was an easy option and made running cable a simple task. I joined the cable afterwards including heat shrink tubing over the connections to make a watertight and snug finish.

I made a rough diagram of the controller dimensions on the wall and realised afterward that they supplied a pattern which I could have used instead. The controlled just surface mounts to the wall. It consumes very little power and constantly displays the ambient air temperature inside the RV cabin, whether the heater is switched on or off. The temperature display allows you to heat up to a very tropical 30 degrees. It also has the capability to circulate air, without the heater running. A feature that is useful for mainly marine installations.

Some Other TIps And Tricks You Might Find Helpful

The stainless steel exhaust pipe provided can be easily shaped around quite sharp corners. Using a screwdriver of the same I.D of the pipe, push the pipe over the screw driver, mount the screw driver in a vice and then holding the pipe, bend it to the angle required, without crushing the pipe ID.

The internal surface of the stainless steel pipe is “screwed” somewhat. If you need to make sure no exhaust gasses escape (as with this installation because the outlet gas pipes were in the cavity that my cabin air comes from) run a product like Maniseal exhaust sealant on the inside of the pipe over the area which will be clamped to the heater port. After about 30 minutes of open air drying, it can be sanded lightly, making it impossible for any exhaust gases to escape through the inside pipe threaded indentations. When Maniseal is squeezed from the tube, its consistency is similar to toothpaste, but it hardens considerably more when it is heated and then becomes rock hard, like body filler or bog.

There is a ring of steel underneath the heater mounting plate. If you have to fit the combustion inlet and exhaust pipes after the heater mount is screwed to the floor, tightening the clamps can be difficult. Using an angle grinder, it’s possible to cut out a small section of this circular rim so that it’s easier to get a socket in to tighten.

The electric fuel pump makes a familiar “click... click” sound as it pumps fuel to the heater. It clicks faster depending on the heat required. The fuel pump is mounted inside a very soft rubber mounting ring which absorbs most of the vibration from the ‘pumping’ action. While most of the vibration is absorbed, some noise escapes. As the heater fan is so quiet when running on low, you may hear the pump clicking away in the still of night. The addition of sound deadening material around the fuel pump can deaden the faint pump noise almost completely.

It's been observed that if the installation does suffer problems, there is a good chance it's related to fuel supply - either a blocked fuel filter, because of dirty fuel and or other fuel related issues. Eberspacher don't recommend running the furnace, despite it being fitted with a filter, when refilling your diesel tanks. The obvious reason for this is that the contents of your tank are being stirred up and you may attract dirty fuel into the filter, which is quite small.

Switching the heater on for the 1st Time - How it performed

Running the heater for the first couple of times, you will get a little smoke coming off the stainless steel exhaust tubing, the result of lubricating oil used in the manufacturing process.

On my 10.6m RV, the cabin temperature took about 20 minutes to increase from 10 degrees C to a very comfortable 20 degrees C. The air temperature coming out of the warm air outlet (on full heat) gets up to 80C. Once the set point temperature was almost achieved, the blower speed starts to reduce, as does the amount of fuel used and the heat produced. When the heater dropped down to low mode and had settled into its 'sweet spot', the air temperature coming out dropped down to about 35 degrees C.

Even with an outside temperature of zero degrees, the heater continued to run on its lowest speed and fuel setting for about 50 minutes each hour. Occasionally, it gradually increases speed, for about 10 minutes every hour, once it senses it is losing the battle to maintain a delicious 20C degree cabin temperature. Then afterwards it dropped back to low mode again.

The furnace is well engineered and it is surprising how cool the plastic outer heater cover remains while the heater is running.

Running the heater without the muffler doesn't make a big difference to the noise level produced, I’ve been told it acts more as a spark arrestor.

Final Thoughts

This heater is not cheap, but it's also very well designed and both quiet and very efficient.

It’s very convenient to use if fuel is being supplied from your existing diesel fuel tank. You will hardly see a drop in your fuel gauge, unless you are using it 24 hours a day. Because of the 5,000 hour expected life cycle, you can install it and forget it (other than a few simple services along the way).

I’m very pleased with my purchased and highly recommend the Eberspacher product. The D4 is a great match for my size vehicle.


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