Webasto Thermo Top EVO Retrofit: Stand Heater and Hydronic Heating

Introduction

The Webasto Thermo Top EVO is a versatile parking heater used not only for engine pre-heating, but also for various hydronic heating systems in vehicles such as cars, RVs and boats. Although new units cost around €1600, used ones can be found at junkyards and marketplaces for as little as €100 – €200. With a W-Bus converter, you can easily use this heater in an aftermarket setup.

This comprehensive guide covers various applications, including:

• Engine pre-heating for cold starts and fuel economy.

• Hydronic heating in RVs and boats.

• Hot water supply by coupling to a water heater.

• Space heating via radiators or convectors.

• Diagnosis and reading of fault codes via Webasto software.

Applications of the Webasto Thermo Top EVO

1. Engine pre-heating

In many modern vehicles, the Webasto Thermo Top EVO is used as a standard engine preheater. This system heats the engine’s coolant circuit, resulting in:

• Faster engine warm-up on cold starts.

• Less wear due to better lubrication at starting temperature.

• Fuel savings as the engine works more efficiently.

• Fewer emissions because the catalytic converter and particulate filter reach operating temperature faster.

For retrofit installations, the heater can be connected to the engine’s coolant circulation system. This preheats the engine without running, which is ideal for winter conditions.

2. Hydronic heating in an RV

For RV owners, the Thermo Top EVO offers an excellent solution as a hydronic heating system. Instead of heating air like an air heater, the Thermo Top EVO heats water in the cooling circuit. This heated water can be used in a variety of ways:

• Underfloor heating: the hot water can circulate through a network of pipes under the floor.

• Convectors or radiators: A classic hydronic system with radiators emitting heat.

• Air-water heat exchangers: A heat exchanger with fans can blow warm air into the RV.

This type of heater provides constant, even heat without dry air, ideal for people spending long periods of time in an RV.

3. Heating a hot water heater

Another common application in RVs and boats is heating a water heater with the Webasto Thermo Top EVO. This can be done in the following ways:

• Indirect heating: The Thermo Top EVO heats the cooling water, which heats the boiler via a heat exchanger.

• Direct heating: Some boiler models support direct connection of the heated coolant.

This system ensures that you always have hot water for showering and washing dishes, without the need for a separate electric water heater.

4. Hydronic heating in a boat

On boats, Thermo Top EVO can be used for both space heating and hot water supply. Advantages of this system on a boat:

• Heats staterooms and sleeping quarters via convectors or air-water heat exchangers.

• Can be integrated with existing heating systems, such as marine central heating.

• Low power consumption compared to electric heating options.

For boats with a 24V electrical system, it is important to check whether the Thermo Top EVO is suitable or requires a power converter.

Diagnosis and Readout of the Webasto Thermo Top EVO

In addition to installation and operating applications, diagnosis and fault code reading is an essential part of maintaining the Thermo Top EVO. With proper diagnostic equipment, you can troubleshoot, clear fault codes and read parameters.

1. Using Webasto Diagnostic Software

Using the Webasto Thermo Test Software, as listed on disco3.co.uk, you can:

• Read and clear fault codes to correct malfunctions.

• Read temperatures and operating parameters for optimal operation.

• Testing the circulation pump and combustion turbine.

• Manually start and stop the stove.

This software is a powerful tool for do-it-yourself diagnosis and repair, allowing you to potentially avoid costly workshop visits.

2. Alternative Diagnostic Methods with a KKL Interface.

Although Webasto offers its own USB diagnostic tool, it is possible to connect to the heater with a cheaper KKL interface (OBD2 to USB).

• Compatible KKL adapters: many OBD2 KKL interfaces compatible with Volkswagen or Audi can also be used for Webasto diagnostics.

• Connection to the diagnostic port: By using an adapter with correct pinout, you can connect the KKL interface to the diagnostic input of the Webasto Thermo Top EVO.

• Software use: The same Webasto Thermo Test Software also works with these KKL adapters.

Pinout for connection:

To correctly connect the KKL interface to the Thermo Top EVO, use the following pinout:

Thermo Top EVO:

• (6 pin connector) Pin 2 (W-Bus) → Signal for communication.

• (2 pin connector) Pin 1 (Ground → use 2.5mm2 cable
• (2 pin connector) Pin 2 (Power supply 12V → use 2.5mm2 cable and fuse at 20A

KKL OBD USB Interface:

• Pin 4&5 (Ground) → Put these to ground, a 0.75mm cable is sufficient

• Pin 7 (Communication with W-Bus) → Connect this to Pin 2 (W-bus) of the thermo top evo
  
  
• Pin 16 (Power supply) → 0.75mm2 cable is sufficient and fuse at 1A

This method allows you to perform cheaper and easier diagnostics, which is convenient for do-it-yourselfers and hobbyists.

3. Benefits of Diagnosis via Software

Benefits of diagnosis via software:

• Self identify and resolve malfunctions.

• Saving money on diagnostic costs at a dealership.

• Real-time monitoring of stove operation.

• Comprehensive logging for analysis of long-term performance.

By using this method, you can closely monitor the status of the Thermo Top EVO and detect any problems quickly without professional help.