How to fit a diesel heater

Winter camping in the southern states can be a bit chilly, and few things shock the system more than waking up in an RV where the temperature is below zero.

Most RVs now have reverse-cycle air conditioning fitted but they’ll only run on 240v AC power. Fine if you’re at a caravan park, but otherwise you’re stuck having to run a gennie to have warm air circulating in the van.

Thankfully, there are various stand-alone RV heating options to stay toasty wherever you are, provided you have the fuel to run the heater.

Two types of central heating

There are two types of RV heating systems – gas or diesel. Gas heating runs off the gas cylinders you probably already have for running your cooker and fridge, but requires a licensed gas fitter to inspect, test and sign off on the gas lines fitted for the installation.

Diesel RV heaters do not require a licence to install but do obviously need a diesel fuel source to run. For caravans, a diesel tank must be installed but for the majority of motorhomes, the heater can source its diesel fuel from the existing diesel fuel tank.

Before considering a diesel heating system, you need to make sure that you have a space big enough in the RV to install the unit. There also needs to be enough air space around the unit to allow enough cabin air to be drawn in; that is, close enough to where you want to put the heating air outlet and adequate provision for the diesel air inlet/exhaust.

Check with your supplier to see what their requirements for minimum dimensions around the unit are.

DIY know-how required

Even though you don’t need to be licensed to install a diesel heater, you do need a certain level of skill. Not only do you need to drill precise holes in cabinetry for air inlet/outlets and the control unit, you also need to ensure that the exhaust fumes from the heater do not enter the fit-out.

Get any of these things wrong and you’re in trouble. Likewise, if you have a warranty claim down the track, the process will go much more smoothly if you had the unit fitted by an authorised installer.

Each diesel heater brand will have slightly different install methods but the run-down here will give you a general idea of what’s required. Make sure you read the installation instructions that came with your diesel heater before you start, and refer to it often during the install.

Where do you put it?

There are several possible locations for a diesel heater install: the storage area under the lift-up bed is a common spot, while for some fitting the unit under a seat base (in a motorhome) is preferred.

The unit seen here was installed on the underfloor; underneath a cupboard adjacent to the rear bathroom. Air was drawn into the unit from the bathroom area and the heated air outlet on the forward wall of the cupboard.

The key here is to not have the air inlet and heated air outlet close to each other – or the heated air will be drawn into the unit and reduce efficiency. The heater switch was installed high up on the same forward wall as the air outlet.

Complete RV Services in Penrith NSW completed the job.

Assemble the unit first

It’s a good idea to start off by assembling as much of the unit as you can, especially when the heater will be fitted in a tight spot (as we’re doing here). The baseplate, inlet/exhaust pipes and wiring were connected up before it was fitted to the motorhome.

Then it was time to start cutting holes in the RV. As the unit was to go under the motorhome’s underfloor, a hole big enough for the unit to pass though was cut in the cupboard floor. A circular hole was then measured and cut in the underfloor with a hole saw so that the baseplate would fit and therefore allow the combustion air inlet/exhaust, fuel line and power wires to exit the underside of the RV.

The unit then went into position on the underfloor, and the air ducting inlet and outlet holes in the cupboard floor were drilled with a hole saw. Then it was time to check measurements again before taking a big breath and cutting the holes for air inlet, air outlet and control switch with the hole saw. The air inlet and outlet faceplates and control switch were then clipped into place.

Then the air inlet/outlet ducting was threaded though the holes in the cupboard floor and clamped to the unit. Any excess ducting was cut off, and the ducting clamped to the back of the air inlet/outlet plates.

Final steps

The combustion air intake silencer was fitted to the inlet pipe and the unit mounted up high on a chassis rail, tbefore the exhaust silencer was clamped to the exhaust pipe and mounted to the rear as much as possible.

Then the exhaust silencer extension pipe was clamped on.

Then it was time to route the fuel line (with inline fuel pump) under the motorhome to the fuel tank inlet. Some recent motorhome cab/chassis have a dedicated inlet ready to go on the fuel tank; others, like this one, need a T-piece fitted to tap into the fuel line.

Finally, the wiring was hooked up: power and earth wires connected to the house battery (with an inline fuse for power) and wiring fed though from the heater unit to the switch mounted on the cupboard wall.

The fuel system needs to be bled, and then the heater can be fired up to test it’s working. Then a final check around the installation to see that all the wires and pipes are secured and to ensure there are no fuel leaks at connections.

Finally, a cover plate was screwed into place over the heater unit in the cupboard.

Warm winters, here we come…