Whale Underfloor Space Heater 4.3kW Gas and Electric ISO Bulk - AK1937

Whale Underfloor Space Heater 4.3kW Gas and Electric ISO Bulk - AK1937

The Whale® 4.3s (4.3kW) space heater is a compact underfloor gas and electric blown air space heater designed for caravan and motorhome applications (it is not suitable for static caravans).

The heater features a boost setting which varies the heat output depending on the temperature of the vehicle. It continually checks the temperature to establish the best settings to use.

Nominal heat input is 2.9kW on gas and 2.6kW on mains electric. This model can use 2.9kW gas and up to 1.3kW electric simultaneously to provide the best available output.

The Whale® 4.3s space heater is designed to be operated by either the Whale Space Heater Control Panel, the Whale Duo Control Panel or by the Whale iVan® Touchscreen Control Panel.

The heater is designed to be installed with a ducted hot air system, and must not be used in conjunction with any other system.

Please note, this Whale® 4.3s heater DOES NOT have a reset button.

The Whale Underfloor Space Heater 4.3 kW Gas & Electric (ISO Bulk) – AK1937 is installed beneath the floor of a caravan, motorhome or campervan, outside the living space.
Mounting the heater underfloor frees up interior storage while still delivering blown warm air into the habitation area via ducting.

It connects to:

• LPG gas (for gas heating)

• 230 V AC (electric heating)

• 12 V DC (fan & controls)

• Warm-air ducting routed up through the floor to interior vents

• A Whale wall-mounted control panel inside the vehicle

Designed for leisure vehicles using Whale heating systems.

How is it fitted

Important safety notice:
Installation involves gas and mains electricity and must be carried out by a qualified/competent installer in accordance with vehicle and gas regulations.

Before you start

• Isolate LPG, 12 V battery, and 230 V mains

• Ensure the underfloor location is:

  • Clear of road debris risk

  • Away from exhaust systems and moving parts

  • Adequately ventilated

• Tools typically required: drill, hole saw (for ducting), spanners, screwdrivers, sealant, gas-rated fittings

Step-by-step fitting

1. Select the underfloor mounting position

   • Choose a position beneath the vehicle floor that allows:

     • Safe clearance from the road

     • Short duct runs into the living area

     • Easy routing of gas and electrical supplies

2. Mount the heater

   • Secure the heater to the vehicle floor/chassis using the approved mounting brackets.

   • Ensure the unit is mounted level and firmly fixed.

3. Route warm-air ducting

   • Cut floor apertures for ducting using a hole saw.

   • Connect Whale warm-air ducts to the heater outlets.

   • Route ducts upwards to interior vents, avoiding sharp bends.

   • Seal floor penetrations to prevent water ingress.

4. Connect gas supply

   • Connect the heater to the vehicle LPG system using approved gas pipework.

   • All gas connections must be leak-tested and certified.

5. Connect electrical supplies

   • 12 V DC: powers fan and controls

   • 230 V AC: powers electric heating element

   • Secure all wiring away from heat and road spray.

6. Install the control panel

   • Fit the Whale control panel inside the vehicle at a comfortable height.

   • Connect it to the heater using the supplied control loom.

7. Commission and test

   • Restore gas and electrical supplies.

   • Test operation in:

     • Gas mode

     • Electric mode

     • Fan/thermostat control

   • Check airflow at all vents and verify safe operation.

Quick fit notes 

• Product type: Underfloor gas & electric blown-air space heater

• Heat output: Up to 4.3 kW

• Installation location: Underfloor (external to living area)

• Connections required: LPG, 12 V DC, 230 V AC

• Air distribution: Warm-air ducting into habitation area

• Control: Whale interior wall-mounted control panel

• Installation: Professional / qualified installer required

Pro tip

Underfloor heaters perform best when duct runs are short and well balanced. Seal all floor penetrations thoroughly to prevent drafts, moisture ingress, and road noise.