Truma Combi (E)
The Truma Combi (E) is a fan-assisted liquefied gas warm-air heater with an integrated 10-litre hot water boiler and, in 'E' variants, additional heating elements for 230V electrical operation. It provides simultaneous or independent space heating and water warming for caravans and motorhomes.
Technical Specifications
Master Troubleshooting & Diagnostics Matrix
| Error Code / Indicator | Symptom / Meaning | Step-by-Step DIY Fix | Suggested Actions |
|---|---|---|---|
Operational Fault | Limescale buildup inside the water container. | Descale the water system using appropriate descaling products (see maintenance instructions). | DIY Safe |
Extremely long heating-up time | Limescale buildup inside the water container. | Descale the water system using standard descaling agents or citric acid. | DIY Safe |
Operational Fault | The safety/drain valve (FrostControl) is open. | Ensure temperature at FrostControl is above approx. 7 °C (or turn on heater), then close the safety/drain valve using the pushbutton. | DIY Safe |
Operational Fault | The safety/drain valve (FrostControl) is open. | Ensure the temperature at FrostControl is above approx. 7 °C (or switch on the heater), turn the rotary switch to 'Operation' and press the pushbutton until it engages, then close the water taps once filled. | DIY Safe |
Operational Fault | The safety/drain valve (FrostControl) is open. | Close the safety/drain valve. | DIY Safe |
Operational Fault | The drainage socket of the safety/drain valve is blocked by dirt, snow slush, ice, or leaves. | Check the drainage opening for obstructions and remove any debris. | DIY Safe |
Operational Fault | Water pressure is too high (exceeding maximum 2.8 bar). | Check pump pressure. If connected to a central/city water supply, install a pressure reducer to limit pressure to max 2.8 bar. | DIY Safe |
Operational Fault | The temperature at the FrostControl valve has dropped below approx. 3 °C (opens automatically) and cannot be closed manually until it reaches approx. 7 °C. | Switch on the heater to warm the installation compartment and FrostControl until its temperature exceeds 7 °C, ensure rotary switch is set to 'Operation', then push the button until it engages. | DIY Safe |
Boiler cannot be drained | The drainage socket of the safety/drain valve is blocked by dirt, slush, ice, or leaves. | Check the drainage socket opening for obstructions and remove any dirt or ice. | DIY Safe |
Operational Fault | Water pressure is too high (exceeding max. 2.8 bar). | Check pump pressure and install a pressure reducer if connected to a central/city water supply. | DIY Safe |
FrostControl cannot be closed | Temperature at FrostControl is below approx. 7 °C or rotary switch is not in the 'Operation' position. | Switch on the heater to warm the installation compartment above 7 °C, turn the rotary switch to 'Operation', and press the pushbutton until it engages. | DIY Safe |
Extremely long heating time | Limescale accumulation inside the water container. | Descale the water system using suitable commercial descaling products. | DIY Safe |
Operational Fault | The draining socket of the safety/drain valve is blocked by dirt, slush, ice, or leaves. | Check the opening for soiling and clean it if necessary. | DIY Safe |
Operational Fault | Ambient temperature at FrostControl has dropped below approximately 3 °C. | Switch the heater on, use the FrostControl heating element, or wait until ambient temperature rises above 7 °C to close it. | DIY Safe |
Operational Fault | Water tank is scaled up | Descale the water supply system | DIY Safe |
Operational Fault | Safety/drain valve is open | Close the safety/drain valve | DIY Safe |
Operational Fault | Water pressure is too high | Check pump pressure - max 2.8 bar, use pressure reducer if connected to central water supply | DIY Safe |
Operational Fault | Temperature below approx. 3 °C and reset conditions not met | Wait until temperature reaches approx. 7 °C to close, or use the FrostControl heating element | DIY Safe |
N/A | Water taking an extremely long time to heat up Possible Cause: Water container furred | Descale water system using commercial descaling products, vinegar essence, or citric acid as outlined in the maintenance instructions. | DIY Safe |
N/A | Water running off – boiler cannot be filled Possible Cause: Safety / drain valve open | Close the safety / drain valve by ensuring the rotary switch is set to operation and pressing the pushbutton until it engages. | DIY Safe |
N/A | Boiler cannot be drained, even though the safety / drain valve is open Possible Cause: Safety / drain valve drainage socket blocked | Check opening for soiling such as slush, ice, or leaves, and remove obstruction if necessary. | DIY Safe |
N/A | Water dripping / flowing from drainage socket of the safety / drain valve Possible Cause: Water pressure too high | Check pump pressure to ensure it does not exceed 2.8 bar. If connected to a central water supply, install a pressure reducer to prevent pressures higher than 2.8 bar. | DIY Safe |
N/A | After the heater has been switched off, the FrostControl opens Possible Cause: Temperature at the FrostControl dropped below approximately 3 °C, causing it to open automatically | Switch the heater on to warm the installation compartment. Without heater operation, the FrostControl cannot be closed again until the temperature reaches approximately 7 °C, or use an optional heating element for FrostControl. | DIY Safe |
N/A | The FrostControl can no longer be closed Possible Cause: Temperature at FrostControl is less than approximately 7 °C, or the rotary switch is not set to operation | Switch the heater on to warm the environment above 7 °C, or turn the rotary switch of the FrostControl to the operation position and press the pushbutton until it engages. If the issue remains unresolved, contact an authorised service agent. | DIY Check / Tech Fallback |
Frequently Asked Questions
Q: Can the Combi be operated without water in the tank?
Yes, interior heating is possible both with and without water content, depending on the operational setting.
Q: What should I do if I smell gas inside the vehicle?
Immediately avoid ignition sources (extinguish naked flames, do not operate electrical switches, phones, or radios, do not start the engine), open windows and doors, evacuate all persons from the vehicle, shut off gas cylinders or the external gas supply, and have the entire system inspected and repaired by an expert.
Q: How do I protect the water boiler from frost damage?
If the vehicle is not in use during freezing periods, you must completely drain the water container via the safety/drain valve (FrostControl or manual drain valve). The system does not feature an internal active frost protection mechanism that prevents freezing without draining.
Q: What should I do if I smell gas in the vehicle?
Avoid ignition sources (extinguish naked flames, do not operate electrical switches, phones, or radios, do not start the engine), open windows and doors, evacuate all persons from the vehicle, shut off gas cylinders from the outside, and have the entire gas system inspected and repaired by experts.
Q: Can the Truma Combi be operated while driving?
Yes, provided an appropriate safety shut-off device like the Truma MonoControl CS gas pressure regulator is installed in accordance with UN ECE Regulation 122 to prevent uncontrolled gas escape during an accident.
Q: How do I protect the boiler from frost damage?
The Combi has no built-in frost protection. If there is a risk of frost and the vehicle is not in use, you must switch off the water pump, open all hot water taps, and open the FrostControl safety/drain valve to completely drain the 10-litre water container.
Q: How do I reset the 230V overheating protection on Combi E models?
Allow the heater to cool down, remove the electrical connector cover, and press the reset button located on the switch.
Q: Can the Truma Combi heat the interior without water in the boiler?
Yes, interior heating is possible both with and without water in the boiler depending on your operational setup.
Q: What should I do if I smell gas?
Extinguish all naked flames, do not operate electrical switches or mobile phones, open windows and doors, evacuate the vehicle, close the gas cylinders, and have the system inspected by an expert.
Q: How do I reset the 230V overheating protection?
Allow the heater to cool down, remove the connection cover on the power electronics, and press the reset button.