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Eberspacher Espar Technical Webasto

Inland Marine Heating Survey Results

Technical Information

SUBJECT:  Inland Maine Heating – Survey findings

marine heating survey

Eberspacher UK conducted a 2-year survey on UK Inland Waterways vessels to identify the main causes of marine heating failure and underperformance. It is very reasonable to assume these findings are relevant in whichever country diesel fired heaters are in service, and applicable to both Eberspacher (Espar) and Webasto heating installations.

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The following were identified as the main causes of marine heating failure or underperformance.

  1. Poor installation
  2. User error
  3. Fuel issues and fuel system
  4. Voltage

These identified causes highlight the following recommendations.


Eberspacher Marine Heater Selection Guide 2022
  • To ensure safety and correct functioning, installation of the heating unit and associated fuel and plumbing to be in accordance with heater manufacturers’ installation parameters.
  • It is recommended a qualified or experienced person be engaged in the system design and/or installation process.
  • Fit the correct heater size (i.e., appropriate kW heat output)

User error

Webasto heater controllers
  • All users should be fully conversant with the operation of the heating system and its limitations. Operating instructions should be read and understood.
  • Heating systems to be serviced regularly by a qualified person
  • To avoid heater short cycling (overheating) a secondary water circuit to be available when heater is used to only heat hot water (e.g., towel rail).

Fuel systems and fuel

Marine Water Heater Installation Diagram
  • Clean fuel to be used from a reputable supplier.
  • Ensure no water can enter the fuel system
  • Fuel left to stand for long periods should be treated for water contamination and/or diesel bug.
  • Standpipes to be installed to manufacturers’ instructions and no lower than the engine fuel pickup.


  • Do not allow the heater to short cycle (switch on and off at short intervals, usually due to overheating) as this will run down batteries. See heater manufacturers’ instructions.
  • Water heaters should not be controlled via an ambient room temperature sensor.
  • Ensure all power cables are of the correct specification to avoid undervoltage.

The above is a brief overview of requirements and recommendations. Specific heater model installation parameters can be found within the Butler Technik website.

Comments and details of your own experiences are welcomed.

Michael BurgessDavid Butler
Technical AuthorDirector
Inland Waterways Marine Heating Survey Results
Article Name
Inland Waterways Marine Heating Survey Results
Technical release. A 2 year survey of UK Inland waterway vessels reveals the main causes of marine heater failure or underperformance. Butler Technik provide the recommended actions to ensure optimal performance of inland boat heating.
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Butler Technik
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