What the D 4 E combines
Truma Combi D 4 E (Next Generation) combines diesel space heating, 230 V electric heating and a 10 L domestic hot-water tank in one appliance.
That makes it different from a stand-alone diesel air heater: it is both cabin heater and water heater. It is also different from the gas Combi 4 E because the fuel burner uses diesel instead of propane/butane.
Four diesel heat levels
Truma publishes diesel heat outputs of 1,000, 2,000, 3,000 and 4,000 W. Fuel consumption is 0.1–0.4 L/h.
These are operating levels, not a fixed hourly fuel burn for every night. The thermostat and control system adjust operation according to the requested temperature and conditions.
Electric heating at a powered campsite
The built-in 230 V heating elements provide 900 W or 1,800 W. Truma lists corresponding current consumption of 3.9 A and 7.8 A.
MHS explanation.A campsite with a 6 A supply cannot support the 1,800 W level by itself. Available shore current and simultaneous appliances still have to be managed.
Mixed mode
The heater can combine diesel and electric energy in mixed operation. Truma publishes up to 3,800 W for mixed-mode rated output on this model.
It may seem surprising that the number is below the 4,000 W maximum diesel stage. The correct approach is to keep the manufacturer's published mode ratings separate rather than adding electrical and diesel numbers ourselves.
Hot water: integrated 10 L tank
The internal stainless-steel tank stores 10 L of water. Truma lists about 20 minutes to heat the water from approximately 15°C to 60°C in water-only operation.
That 10 L is hot-water storage inside the appliance, not the total mixed water available at the shower. The final useful volume depends on cold-water temperature, mixing ratio and flow.
Diesel use does not eliminate electrical demand
The 12 V system powers fans, controls and fuel-system components. Truma lists 0.4–8.1 A during heater/water operation and about 1 mA quiescent current.
For winter autonomy, diesel volume and battery energy therefore both matter. A full vehicle or auxiliary fuel tank cannot compensate for a flat house battery.
Airflow and ducting
Maximum free-blowing warm-air flow is 287 m³/h through the intended warm-air distribution system.
In the real camper, duct length, bends and outlet placement affect how evenly heat reaches different areas. The published airflow should not be treated as a guarantee that every sleeping corner receives the same temperature.
Pressure sensor and altitude
The next-generation diesel Combi includes an integrated pressure sensor that automatically adjusts combustion-air supply. Truma highlights this as enabling operation at altitude.
MHS explanation.This is a feature of the heater, not permission to ignore fuel quality, exhaust installation or local operating limits. The complete installation still has to follow the applicable manual.
Controls
The unit can be controlled through Truma CP plus (iNet ready) or the iNet X System, depending on the installed control setup.
A camper brochure that names only Combi D 4 E does not prove which control panel is included. MHS separates the heater model from the controller unless both are explicitly documented.
Water and pressure limits
The product page lists maximum pump pressure of 2.8 bar and maximum system pressure of 4.5 bar.
These are limits for the integrated water system. Do not set the camper pump to the maximum simply because the heater can tolerate it; the other fittings and fixtures have their own requirements.
Size and payload
The heater weighs 16.8 kg and measures 510 × 450 × 300 mm. Truma lists a minimum installation envelope of about 540 × 500 × 350 mm, with additional space needed for connections.
This distinction matters in a compact pickup camper. Product body dimensions do not include all the space needed for fuel, water, exhaust, air ducts and service access.
What to check in a camper
Confirm the full label Combi D 4 E (Next Generation). Check how diesel is supplied, which 230 V shore circuit feeds the electric elements, and which Truma control panel is installed.
Run space heating and hot water separately during handover. If mixed mode is important, test it on a suitable shore connection. Also learn the winter drain procedure for the 10 L water tank.
Key takeaway
Combi D 4 E is a compact diesel/electric heating and hot-water system. Its real autonomy depends on diesel, 12 V battery energy, shore power when used, water and a correctly designed warm-air/exhaust installation.
Source
Truma — Combi D 4 E (Next Generation)
Next-generation Truma Combi D 4 E only. Do not transfer Combi D 6 E output or older-generation specifications.