Choosing the Best Diesel Hot Water Air Heating Fan Head

Choosing the Best Diesel Hot Water Air Heating Fan Head

Hydronic systems in boats or RVs use fan heads to transfer heat from the hot circulating coolant to the air. Fan heads come in different sizes and power ratings, so selection is a case of getting the correct power output and physical size to fit. 

We use a range of fan heads from Kalori and also ducted ones we make ourselves.

The Kalori fan heads are face fixed in a cupboard or bulkhead so tend to be more space efficient, but are generally not as powerful as the ducted units. The ducted units are slightly bulkier due to larger heat transfer coils. This is often not an issue since they can be mounted in dead space which is not useful for general storage and then the hot air is ducted forward to a small 60mm hot air vent.

One of the benefits of all hydronic air heating systems is that you can easily mount the fan heads remote from the hot water system, or you can use multiple fan heads to spread the heat or heat multiple spaces or zones.

For all fan heads an open return air pathway is very important because the fans need a free flowing inlet air pathway to work efficiently.

The Kalori fan heads use a 2 speed axial type computer fan which tends to be slightly noisy on high (up to 60dB), but is quieter on the low speed setting. The Dieselheat ducted fan uses an EC controlled drum fan which has infinitely variable speed and is quieter overall (max 51dB). The advertised Kalori fan head heating power ratings are based on theoretical situations, the table below sets out real life power outputs for the fan heads to assist in selecting the best fan head for your application.

Both the Kalori fan heads and the Dieselheat ducted fan can be controlled by the Dieselheat Hydronic Thermostat to give 3 manual power levels (which are adjustable) and an automatic mode to regulate the room temperature. This is beneficial for the Kalori fan units as the maximum speed can be set to approx 80% of fan power which still gives off most of the heat, but is quieter.

Fan Unit
Real Heat Output*
Max Noise**
Suggested Use
Kalori Silencio FA

Kalori Silencio FA



Small bathrooms in boats or RVs, small vans eg Volkswagen T6

Kalori Kuba VA200

Kalori VA200



Small boat living spaces, larger vans (sprinter, transporter), small caravan.

Kalori Silencio 2

Kalori Silencio 2



Larger living spaces in boats, larger caravans up to about 20 foot.

Kalori Silencio 2

Dieselheat 1.8kW Ducted Fan



Boat saloons, caravans up to 20 foot, larger spaces.

Kalori Silencio 2

Dieselheat 3.6kW Ducted Fan



Caravans over 20 foot, large boat saloons, spaces in cold climates.

*Heat outputs are based on measurements by Dieselheat in our workshop in real world conditions. We assume 70 degree coolant and 20 degree air. 

**Noise measurements are done in our workshop with simple equipment, they measured 1m from the fan head front and slightly offset with the unit installed in a wooden box to simulate real world conditions.


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