Truma Combi 4 & 6 E Guide

The Truma Combi 4E and 6E combines heating space and water in one system. It’s a clever piece of equipment which you want to make sure you are maximising the usage of. In this guide we will discuss it’s uses, the different functions and setting and answer some troubleshooting questions.

What is the Truma Combi 4E & 6E?

The Truma Combi 4 and 6 E, like all Combi models in the Truma range, combines space and water heating into one appliance - a brilliant space and weight saving solution for modern caravans and motorhomes. The system can warm a space up in just a few minutes, as well as heat any water you need for showering and washing dishes.

The Combi 4E and 6E system uses very little electricity and so the heater can easily run off the 12V power supply unit without the vehicle battery. The heater runs in gas mode for self-sufficient use, perfect for if you’re staying off-grid. If you’re staying at a campsite with hookup it’ll run in electrical mode and in mixed mode when outside temperatures are low.

How does the Truma Combi 4E & 6E work?

The Truma Combi 4E and 6E is controlled via the LCD control panel, from here you can set timers, turn the water or heating on or off, and set temperatures. The heater is connected to the gas supply of the vehicle via the gas connection. The gas supply to the heater is controlled via the solenoid valve . The required combustion air enters the appliance through the outer duct of the combined combustion air/exhaust cowl and is fed to the gas burner with the help of the combustion air fan . The gas burner, which has two ignition electrodes and a flame rectification electrode, ignites the gas-air mixture in the combustion chamber.

The hot exhaust gases are diverted at the end of the combustion chamber on the baffle of the flame tube and flow back between the flame tube of the burner and the inside wall of the heat exchanger. They are fed to the atmosphere via the exhaust cowl.

The circulation fan blows the air that is to be heated into the appliance. There, the air flows along the fins of the heat exchanger which ensures optimum heat transfer because of its large transfer surface area. Inside the heat exchanger are additional 1800 W electric heating elements. They can be used to heat water and/or warm air alternatively or additionally. The warm air is then distributed in the vehicle via four warm air outlets.

Fresh water is in the outer stainless steel water container, which holds up to ten litres. It is heated by the heat transfer from the heat exchanger. Because of the eccentric shape of the water container, the warm water circulates, which ensures optimum mixing of the water and better thermal stratification. The warm water connection pipe connects the Truma Combi with the hot water lines in the kitchen and bathroom. Cold water is pumped from the freshwater tank via the cold water connection pipe.

The room temperature is monitored via a sensor located in the vehicles, whilst the water temperature is measured by internal temperature sensors. The appliance reduces the heat output before the desired heating and water temperatures are reached - at which point the burner switches off. When the temperature falls below the set heater and water temperatures, the Truma Combi switches on again automatically to heat air and water (winter mode). In summer mode it is possible to heat up the water independently of the space heater. The HDF thermal jacket provides good insulation for the Truma Combi heater.


Truma Combi 4E & 6E FAQ’s

In summer, can the Truma Combi heater heat just water without heating the living area?

Yes. Simply switch the heater into summer mode and select 40 or 60 degrees Celsius water temperature. When the yellow LED on the control panel goes out, the respective water temperature is reached. The heating system heats only water and the circulation fan does not run. Output in summer mode is 2 KW.


Can I also heat the living area with my Truma Combi heater if it is not filled with water?

Yes. The Combi heater may be used in pure heating mode even with an empty water container.


Does the water container on the Truma Combi heater need to be sterilised and descaled?

The water container on the Truma Combi heater should be regularly sterilised and descaled. Any standard cleaning products stocked by specialist camping retailers can be used for cleaning, sterilisation and maintenance. It is important that products are used according to manufacturer specifications in the correct dosage and with the correct exposure time.

You can also regularly heat the water in the Combi heater to 70°C to prevent the growth of microorganisms. To do this, set the water temperature to 60°C (on the CP plus control panel, HOT setting), leave the appliance switched on for at least 30 minutes, and do not use any hot water during this time. Once the water reaches a temperature of 60°C, the burner switches off and the residual heat in the heat exchanger heats the water to 70°C.

You can use standard descaling products from specialist camping retailers, acetic acid or citric acid to descale the water container. Add the cleaning or descaling products in the recommended mixing ratio to the appliance via the water intake and allow them to work. Then flush the Truma Combi as part of your water system thoroughly with fresh water.


Why does the circulating air motor keep running after the heater is switched off?

This function protects the unit from possible overheating caused by heat build-up. The circulating air motor gives off the possible heat build-up into the vehicle interior during the after-run period. Please note that this after-run occurs every time the Trumatic C is switched off, even after extremely short periods of operation. Remember: The fan after-run cannot be deactivated.


Do I use less gas when I run the Truma Combi 6 E in mixed mode?

It is correct that you consume less gas in mixed mode, as the Truma Combi heater tries first to reach the set temperature in electric mode. If the camp site offers a fixed price electricity rate, mixed mode is especially advisable.


Can Truma heaters also be operated while I’m driving?

Yes, heating while driving is possible with Truma Combi and VarioHeat heaters.

With Truma S and Trumatic S heaters, operating the heater while driving is possible only with a cowl top, which must be installed freely in the air flow. Truma recommends the cowl tops T-3 or T-2. Otherwise the flame can blow back and cause damage to the heater. The cowl top must protrude at least 10 cm above roof attachments, such as roof boxes, ski or luggage racks so that the heater works properly.

For heating while driving, Directive UN ECE R 122 for motorhomes and caravans specifies a safety shut-off device. The Truma MonoControl CS gas pressure regulation system fulfils this requirement. Throughout Europe, a type-tested LPG heater may be used while driving (according to Directive UN ECE R 122) if the system includes this regulator with an appropriately configured gas installation. National regulations must be observed.


Why has the Combi E automatically drained the water?

Check to see if you have a Truma Frost Control frost protection safety valve, for more information and instructions on this click here.


With the Combi E, can a warm air outlet or warm air duct be completely closed off?

To prevent heat accumulation, no warm air outlets or warm air ducts must be closed off on the Combi 6E. With the Combi 4E no more than one warm air outlet or warm air duct may be completely closed off. But it is always better to use all four warm air outlets. Individual outlets in the same pipe may be closed only if T/Y-pieces are used and the heat can be directed to another open warm air outlet.


Does the heat exchanger of a Truma LPG heater have to be replaced after a certain time?

No. Neither the European Heating Appliance Directive 2006/119/EC nor the international directive UN ECE R122 specify replacement. In the 1990s there was a German regulation which specified that heat exchangers had to be replaced after ten years. For Truma heaters manufactured and put into operation during this time, the replacement obligation was prolonged to 30 years. The European Heating Appliance Directive no longer specifies replacement for appliances approved after 06/2005.

The E1 mark on the type plate shows whether your heater is approved in accordance with the European Heating Appliance Directive and, consequently, was manufactured after 06/2005.


Warning W 255 H appears in the display of the CP plus panel – what should I do?

The heater does not have 12 Volt power supply or there is no connection between the heater and the CP plus control panel. The power supply to the heater may have been interrupted by switching off the vehicle control panel (not the Truma heater control panel).

The control panel is used to control all other functions in the vehicle and it also switches the power supply for the consumers in your vehicle on or off.

  • In this case turn on the control panel in your caravan to re-establish power supply for the heater.
  • Once the power supply is guaranteed and the warning is still present, check the cable connection between the heater control panel and the heater.

Error 621 appears in the display of the CP plus panel – what should I do?

Error E 621 H means that the room temperature sensor defect or not connected. This error is displayed flashing during the first commissioning of the heater.

Warning 621 flashes because the heater is in a 15-minute lockout period.

  1. Wait until the 15-minute lockout period is over. Please do not switch off the control panel during this period and do not interrupt the power supply.
  2. As soon as the lockout period of the heater is over, the error is no longer blinking but permanently displayed.
  3. Delete or acknowledge the error code:
  4. Briefly press the rotary push button on the CP plus (the backlight will be activated when the button is pressed if the control panel was in standby mode)
  5. Press the rotary pushbutton briefly again (malfunction / error is acknowledged by pressing it again)

  6. The warning E 621 H is displayed constantly and appears again after the acknowledgement


  7. The fault 507, 516 or 517 appears in the display of the digital control panel CP plus – what must I do?

    Remedy fault 507 / 516 / 517 means that the gas supply has been interrupted.

    • Restore the gas supply, for example by connecting a full gas cylinder.
    • Then confirm or delete the fault code by tapping the rotary push button. Please note that the first tap might only activate the backlighting of the control panel.
    • The heating then starts automatically if there is a heating requirement.
  8. Note: If the fault 507, 516 or 517 is displayed in the heater's control panel, switching the control panel on and off does not help. This does not delete the fault, but blocks the heater for 15 minutes. The heater is also blocked for 15 minutes if the fault 507, 516 or 517 is deleted four times without the gas supply being established.

    Remedying flashing fault 507 / 516 / 517 (gas supply interrupted) The fault code 507, 516 or 517 flashes because the heater is still in a 15-minute blocking time. This was possibly caused by the heater control panel being switched off or because the heater's 12-Volt supply was interrupted. The heater is also blocked for 15 minutes if the displayed fault is deleted four times without the gas supply being restored.

    • Wait out the 15-minute blocking time for the heater. During this time, do not switch off the heater's control panel and also do not interrupt the power supply.
    • As soon as the heater's blocking time has expired, the fault is then displayed permanently rather than flashing. It can now be deleted as described in the point above.

  9. Warning W 412 H or W 42 H appears in the display of the CP plus panel – what should I do?

    Your heater includes a window switch which prevents the heater from starting up if the side window above or right next to the wall cowl of your heater is not completely closed.

    • Please check that the window in question is locked when completely closed.

  10. Warning W 408 H appears in the display of the CP plus panel – what should I do?

    If running the Combi E in mixed mode (combined gas and electric heating operation)) then this warning indicates lack of gas supply. The heater now only runs in electric mode.

    1. Restore the gas supply for example by connecting a new gas cylinder.
    2. On your control panel you then switch to pure gas mode of your heating system – the warning message changes to error message 507 or 516.
    3. Remove the error as described here: www.truma.com/uk/en/faq/remedy-fault-507-516-517

  11. An error code is shown on the display of my digital CP plus control panel – how do I find out what it means?

    Click here to visit the Truma page relating to error codes


    Information supplied from truma.com

    While we have made every attempt to ensure that the information on these pages has been obtained from reliable sources, Adventure Leisure Vehicles Ltd is not responsible for any errors or omissions, or for the results obtained from the use of this information. All information on this page is provided “as is”, with no guarantee of completeness, accuracy, timeliness or of the results obtained from the use of this information, and without warranty of any kind, express or implied, including, but not limited to warranties of performance and fitness for a particular purpose. In no event will Adventure Leisure Vehicles Ltd including employees be liable to you or anyone else for the decision made or action taken in reliance on the information on these pages or for any consequential, special or similar damages.

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