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35KW diesel coolant heater 24V – Webasto/Spheros Thermo 350

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The Spheros Thermo 350 coolant heater

A powerful modern coolant heater for large trucks, the Spheros/Webasto Thermo 350 is a great choice. With over 120,000 BTU of heating power, this heater will keep your hydraulic equipment running in temperatures as low as -40°C (-40°F). Powerful and efficient, the Thermo 350 is ideal for heating and maintaining trucks, buses, and construction vehicles. 

User Benefits of the 35KW diesel heater

  • The preheating of high-powered engines increases their life expectancy and readiness for operation.

  • Buses can be quickly heated without running their engines.

  • Keeps the cabin warm and the hydraulics running, even at extremely low temperatures.

  • The Spheros 35KW coolant heater quickly and efficiently heats up coolant and hydraulic liquid, for smooth and comfortable operation.

Keep your water running, coolant flowing, and hydraulics pushing at sub-zero temperatures

It is easy and effective to preheat your engine with the Spheros Thermo 350 forced flow coolant heater. First, the coolant or hydraulic fluid is heated, and then it is pumped through the cycle using an electric pump. As a result, the heat is evenly distributed throughout the entire cycle, ensuring smooth performance.

Especially in very cold temperatures, preheating large diesel engines is necessary, as the engine might not start otherwise. In addition to ensuring the engine will start, preheating reduces fuel consumption, engine wear, and emissions.

The Webasto/Spheros Thermo 350 produces a massive 120,000 BTU of heat. The Thermo 350 consumes minimal fuel and energy thanks to new sensors, an upgraded ECU, and an efficient combustion chamber. Because Spheros Thermo 350 is economical, powerful, and reliable, it is an important tool for combating freezing climates.

The Spheros Thermo 350 coolant heaters are regarded for their efficiency, power, and reliability. More than 150,000 Spheros coolant heating systems have been installed worldwide, which puts Spheros among the industry leaders in large systems heating.

Key Features of the Spheros Thermo 350

  • Includes all the necessary components for a straightforward installation.

  • Supplies 120,000 BTU of heat for preheating the engine, warming up the cabin, and potentially supplying hot water.

  • Minimal fuel and power consumption makes the Thermo 350 economical, long-lasting, and ecological.

  • Advanced Diagnostic System accurately and reliably reports possible errors.

Included in the kit

  • Rheostat controller

  • Fuel Filter

  • Integrated fuel pump

Spheros/Webasto Thermo 350 Technical Specifications

Part Number


Voltage (V)


Fuel Type


Maximum Heat Flow (BTU (KW))

120 000 BTU (35KW)

Fuel Consumption (gallon/hour (liter/hour))

1.19 gal/h (4.5 L/h)

Power Consumption (W)

140 W without coolant pump

Dimensions (L x W x H)

24 x 9.7 x 8.7 in (610 x 246 x 220 mm)

Weight (lbs (kg))

42 lbs (19 kg)