How to install a diesel heater on your boat
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A properly installed diesel forced air heater will keep your boat warm for a long time, with little more than a service every couple of years.
Problems with diesel heaters are most often attributable to how it was installed.
Getting the installation right in the first place is key, therefore.
If you’ve already got heating on board, it’s worth giving it a once over to check that it was put in correctly to start with and that no parts of the system are damaged.
While a crushed vent might reduce the efficiency of your heating, a damaged exhaust could produce fatal carbon monoxide or pose a fire risk.
For those who don’t have heating, carefully planning how you would fit it is the first step.
Getting the right unit will be crucial for the long-term performance of your heating.
A unit that isn’t big enough for your boat will constantly be running at full capacity and will drain power, while a unit that is too big will be in idle much of the time and risks sooting up as a diesel engine would.
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A 2kW heater is sufficient for up to four outlets on boats up to 34ft, while a 4kW heater will be suitable for boats of up to 40ft or more, depending on how many areas you want to heat.
You also have the option of installing more than one smaller heater, so you can have separate heating for different areas of the boat, which may be a more efficient solution.
For this installation on a Sadler 29, an Eberspacher 2kW unit with two vents was plenty.
The heater cannot be in any cabin space and must be in a separate locker, and depending on the make, should be fitted as close to horizontal in both planes as possible.
These requirements mean that the majority of heaters, as on this boat, are fitted in a cockpit locker, tucked up out of the way.
If you store lines and fenders in here, make sure they don’t rest on the system, though the exhaust should be lagged for its whole length.
The ducting leads the hot air around the boat and will lose some heat as it does so.
This isn’t significant where the ducting runs straight, and some residual warmth can help to keep lockers warm and dry, but on long runs or sharp corners, heat lost will be greater, making the heater work harder.
Ducting runs should therefore be as simple and as short as possible, and where sharp corners are unavoidable they should be properly insulated with lagging.
The fixed vent (which avoids the system overheating) on this boat was placed in the saloon by the base of the chart table, and the closing vent forward in the heads where the heat could be directed through to the forward cabin, or to the wet locker.
With the heater in the cockpit locker port aft, the ducting was routed along the engine bay, under the starboard quarter berth and then forward under the chart table into the locker below the starboard saloon berth, where the ducting was split with a Y connector.
Power and fuel supply should be fairly straightforward on most boats as the batteries and fuel tank are usually close to the engine bay.
The exhaust outlet must be at least 300mm above the waterline; the higher the better, as long as there is still space for a swan neck in the exhaust to stop water backflow in rough conditions.
For more information, please visit Split Diesel Heater.
You then also need to think about where fuel, power and air ducting will be routed. the fuel pump needs to be within 2m of the fuel tank and within 4m of the heater, and it also needs to be fitted at between 15° and 30°, which helps prevent air locks.
Adding the fuel lift pipe to the tank, including a shut-off valve, required carefully drilling a hole into the metal tank.
This was done with a vacuum cleaner next to the drill bit to prevent debris entering the tank. the pump has its own small filter, and shouldn’t have an additional in-line filter as this can provide too much resistance to the pump.
The control unit can be located wherever it is most convenient, limited only by the length of the cable, though some wireless control units are available.
Either way, the diesel heater should be within the area that is being heated, but not next to an outlet as this will affect the thermostat. if there is no other option, an external thermostat can be added.
Having the right tools for the job will make installation much easier and neater.
If you are having a professional installation, their experience will pay dividends here, but it’s worth asking if they have done a fitting on your type of boat before.
Most ducting is a standard size, but check requirements for your system. this ducting required a 67mm (2 5/8ths in) hole saw, and the exhaust skin fitting needed a 38mm (1 1⁄2 in) hole saw, which was cut angled upwards, using the stainless skin fitting as a guide, before being fitting with plenty of sealant.
The only issue encountered was discovering some hidden cable ducting glassed into the forward bulkhead, so having a wiring diagram of your boat before you start is a good idea.
The only sharp corners that were unavoidable were under the quarter berth and again as it went through the forward bulkhead into the hanging locker, so both of these were insulated with lagging.
One area of ducting was also unavoidably exposed below the chart table, so a hardwood box was built to protect it.
Covers were screwed over the ducting apertures and the system was ready to use.
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Last year i installed a chinese diesel heater to heat/pre heat my kitchen/conservatory area. it was much better than i expected, being able to control it via the remote made it simple to operate - i could even turn it on from bed when i woke up so the kitchen/conservatory was warm when we got up.
ok, for those who may be thinking exhaust fumes, dangers of catching fire etc .... the heater itself was sited outside and the hot air was fed into our house, under the kitchen units. Initially i had the air intake taking air from the outside, but soon realised i actually needed to take the air intake from INSIDE the house, so installed another ducting run, again under the kitchen units. i also had to use a step down transformer from 240v to 12v DC but as its all under the kitchen units its tucked nicely out of sight.
ive installed the ducting in such a way that the heater can be removed from the patio area when not required and the ducting 'sealed' using end caps.
i 'acquired' a cover for it all so its protected a bit from the elements - its not pretty but it works. it wouldn't take too much to make a permanent enclosure should i ever feel the need. i like the temp enclosure because i can remove it all when the heater isn't needed to boost the temperature up. the temp enclosure also helps in insulating the ducts, i kept the external ducting runs to a minimum so as to reduce heat loss.
Running cost was around a litre of fuel every other day, depending on length of time and of course temp settings, but as a rough guide we used around 5 litres every two or three days for 12 hours running.
Our only other source of heating in that area is an inverter (air con/heating) so the diesel heater took some of the 'strain'
I will definitely be using it again this coming winter, though i may look at installing a bigger fuel tank somehow, prob using a 20 litre paraffin container, so i will only need to fill it up once a week! i use metal jerry cans to get the diesel from the local garage, though i really should look at cheaper fuels such as heating oil or paraffin, but dont know if they would impact on the heater itself, i prob need to check out youtube to see if anyone has used alternative and cheaper fuels (so long as theyre easily obtainable for me!)
if i ever get round to tweaking the system, i will look at ways to recover the heat wasted through the exhaust, which really gets hot. i have seen a few methods on you tube which look simple enough, very 'Heath Robinson', but i like that approach !!
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