Use Combi-Heater in winter with or without water?

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As a camper, questions arise during the winter season such as: “How do I make sure that the water in my heating system or vehicle does not freeze when I am not on site during the day?” or “Can I heat my camper or caravan without water in the boiler?

We answer both questions in this article.

If you are travelling with your vehicle in winter, you can choose between the above options to suit your needs. Both are possible, as long as the operation of the unit is adapted accordingly.

Option 1: If your motorhome or caravan is filled with fresh water, the heating should always remain active. As long as the frost monitor of the Combi, the FrostControl (FC), is exposed to an ambient temperature of >3°C, it remains closed and the water remains in the system. It is important here that the temperature is measured directly at the FC. Experience has shown that it is equally important that only the water runs out of the Combi when the FC is open. Whether the fresh water tank and all water pipes also run empty depends on the installation of the water supply by the vehicle manufacturer. This may or may not be the case. You should check this at your leisure before starting your journey.

You can set 5°C as the lowest room temperature on the heating control. If this is not sufficient to heat the FC because it has been installed further away from the Combi or a warm air pipe, a higher room temperature requirement should be set. This is possible with the CP plus from 5°C in 1°C steps. Simply approach a suitable value slowly. With the CP classic, with the two rotary knobs, level 1 also corresponds to 5°C, level 5 about 30°C. The other levels are in between. Level 2 should therefore be sufficient to keep the FC closed. Please note that such operation is only recommended during a journey. It is not a suitable means of keeping the vehicle frost-free throughout the winter. Short heating times of the heater promote the formation of condensation in the exhaust tract.

If the installation space of the FrostControl is too far away from the heater or completely unheated, a separate heating element for the FC can be purchased from our authorised dealers.

Option 2: If you are travelling without water in the system, the Combi can also be operated. The only important thing here is to set only room heating as a requirement for the Combi. The water heating programme must remain inactive. Make sure that the water tank of the Combi is correctly emptied. Residual water in the combi can get very hot very quickly. The resulting water vapour can irritate the temperature sensors of the heater and lead to a warning message “Water overtemperature detected”. For this reason, we recommend that you leave the FC open when using the vehicle in this way. This way, the water can find its way out of every corner of the fresh water supply during a winding journey. Optionally, you can help by using light compressed air or a balloon that has been put over and filled at the open water taps.

Please note: we recommend both modes of operation only on one trip. Operating the heater in one of the specified options for months should be avoided. The reason for this is that this type of use does not correspond to the intended use of an appliance for camping needs. In addition, under unfavourable conditions, condensation can collect in the exhaust pipe and disrupt the proper operation of the heating system.

With these tips, you’ll be well prepared, even when it’s cold outside. We wish you a wonderful winter holiday.

Reset function on the CPplus

The spanner in the lower right-hand area of the display is used to access the settings menu of the CPplus operating element. And it is here that you will find the menu item “Reset”. However, many people are unfamiliar with its function.

When the CPplus is delivered, it is completely blank with regard to the units to be controlled. The device memory is empty. During the vehicle conversion at the caravan or motor home manufacturer, the vehicle technology is implemented step by step into the body and at some point the gas supply and heating and air conditioning system from our company is also installed. In order to be able to operate and monitor all Truma devices, the device memory in the CPplus must finally be filled. And this is what the reset function is for. By pressing the control knob when “RESET” is shown on the display, I activate this function and “PRSET” appears. Press the control knob again to delete the unit’s memory. After this, “INIT” appears; all units connected to the CPplus with a TIN cable and supplied with voltage at the time of initialisation are now written into the unit memory of the CPplus. Only at this point can they be controlled with the operating element. All symbols belonging to the units are then stored on the display and can be selected.

Please note that a reset is never used to reset an error code. If, for example, the heater reports a gas error ( E506H, E516H or E517H), the reset automatically locks the control electronics of the heater for 15 minutes. If a reset is activated with the warning message W255H, which indicates that the control element has lost contact with the heater, then the CPplus is returned to the delivery state without a connected heater. In this case, the power supply of the heater and the TIN connection cable to the heater should be checked first.

Caution with accessories from the 3D printer

In view of this, we would like to point out that many online portals and trading platforms offer accessory products and 3D files for the manufacture of components that are supposed to improve the function of our Truma devices or remedy side effects. These products may appear to be useful and may be of good quality, but in most cases they have not been tested, authorised or approved by us.

An example of this is the product known as the drip lip / drip guide or condensation drain for mounting on the flue of the Combi heater. It does not come from our company and its installation even invalidates the operating permit and warranty as an unauthorised modification to the appliance.

As described in our operating instructions and the installation instructions, no safety-relevant component may be changed. However, the side wall chimney and its individual components belong to this area. After such a change, the appliance may no longer be put into operation from a legal point of view. Interactions with the accessory product are unknown.

This circumstance can perhaps be compared to the installation of a sports exhaust system for a passenger car: if there is no expert opinion or ABE for the system, in which the vehicle model is not explicitly mentioned, then it is also not permitted to install it. Use on public roads is prohibited. If you are caught, you are also liable to prosecution for “driving without an operating licence”. The consequence is a trip to the TÜV and a fine.

In the case of the above-mentioned accessories, there is no mention of whether the material used can withstand the temperatures applied to the side wall chimney, nor is there any guarantee that the imperative openings for combustion air intake and exhaust gas disposal will be affected in any way. In such cases, for example, due to an incorrectly supplied amount of oxygen or reduced cross-section of the flue gas opening, the burner of your heating system may not work correctly and error messages may occur during heating operation.

In the worst case, damage to the vehicle may occur if, for example, the material of the accessory was not designed for the temperatures on the side wall chimney.

So if in doubt, please contact the Truma Service Centre, our authorised dealers or service partners. Here you can clarify whether such an accessory comes from our production and whether there are justified objections regarding its function or the effect on an existing approval.