Maintaining thermal comfort is essential for year-round independent travel. While smaller camper vans are typically equipped with forced-air heating systems, luxury motorhomes and large coaches generally rely on hydronic heating. Every technology — from classic Truma gas heaters and Webasto diesel heaters to sophisticated Alde hydronic systems — requires a specific operating approach and regular maintenance.
Neglecting your heating system before a winter trip into the mountains can quickly turn a luxury holiday into a survival exercise. This guide explains everything you need to know.
Forced-Air vs. Hydronic Heating
Forced-Air Systems (Truma Combi, Webasto Air Top)
Forced-air heaters draw cool air from the interior, warm it inside an integrated heat exchanger, and distribute it throughout the vehicle via plastic ducts using a high-performance fan. They warm up very quickly and cost less to buy — but the continuous fan noise, dust movement, and uneven temperature distribution (warm ceiling, cool floor) are noticeable drawbacks.
Hydronic Systems (Alde Compact)
Hydronic heating works on exactly the same principle as residential central heating. The boiler heats a glycol-based coolant, circulated by a quiet 12V pump through pipes feeding convectors along the walls or beneath the floor. Heat rises naturally from floor level, walls are gently warmed, and cold spots and condensation are minimised. The trade-off: a much longer warm-up time and higher initial cost.
The Heart of a Luxury Motorhome: Alde Compact
The Alde boiler (Compact 3020 / 3030 series) is a combined heating and domestic hot water system with an integrated stainless-steel tank. Its key advantage is the ability to draw heat from multiple energy sources and intelligently combine them.
Four Operating Modes
- Propane / LPG — a modulating gas burner (typically up to 5.5 kW) provides the primary heat source when camping without mains electricity.
- 230V Electric Heating — integrated electric elements with selectable outputs of 1, 2, or 3 kW. When connected to campground shore power, the entire heating system can operate without consuming any gas.
- Combined Mode — during extremely cold weather, the boiler automatically combines gas and electric heating for maximum output.
- Engine Heat Exchanger — the hydronic circuit connects to the engine cooling system through a plate heat exchanger. While driving, waste heat from the Iveco engine heats the living area, warms the floor, and heats the domestic hot water tank. When you arrive, both interior and hot water are already warm — without burning a single gram of propane.
The Phoenix uses an Alde Compact 3030 feeding convectors in the double floor and along the side walls. In winter I primarily rely on the Iveco engine heat exchanger while driving and the 230V electric elements at campsites. Propane is only used during extended off-grid stays or when I need rapid warm-up on arrival. During long winter journeys, propane consumption is essentially zero — the motorhome is heated entirely by the engine's waste heat.
Heat Transfer Fluid: G12/G13 vs. Premium G13
The fluid circulating through an Alde system is not ordinary water. It must remain liquid down to approximately −35°C, protect aluminium convectors and copper tubing from corrosion, and prevent deposits from forming inside the heating circuit.
Earlier Alde systems commonly used blue-green ethylene glycol coolant with a 2-year service life. Once the corrosion inhibitors are depleted, the coolant begins attacking aluminium components from the inside. Modern Alde-approved coolant (Alde Premium Magenta Antifreeze) uses Organic Acid Technology (OAT) with a 5-year service life. Although replacing 20–30 litres is more expensive, it prevents extremely costly damage to the heating circuit.
Mixing the two specifications may cause the coolant to gel, potentially blocking the entire heating circuit. Always drain completely before switching coolant type, and use only one specification throughout the system.
Bleeding and Maintenance — Step by Step
If your heater produces little heat, you hear gurgling inside the convectors, or one part of the motorhome stays cold, the system almost certainly contains trapped air. Air pockets act like plugs that prevent the circulation pump from moving coolant properly.
After a complete coolant replacement, bleed the system twice. After the initial refill, run the pump at maximum speed again and check the coolant level after one hour of operation — remaining air bubbles gradually reach the expansion tank and the level typically drops by a few millimetres. This is perfectly normal.
Diesel Backup Heating: Webasto and Eberspächer
For serious off-grid expeditions or extended winter camping, the ideal solution is to combine the primary gas/electric system with an independent diesel heater. Propane cylinders eventually run empty, and compatible refill systems vary from country to country. Diesel, however, is always available in the Iveco fuel tank (typically 60–90 litres).
High-end installations use diesel heaters such as the Webasto Thermo Top connected directly to the Alde coolant circuit. The diesel heater warms the same coolant — so convectors, underfloor heating, and domestic hot water continue operating normally even if propane runs out:
A Webasto Thermo Top can also preheat the Iveco engine before starting in freezing weather — dramatically reducing cold-start wear. The engine starts with warm coolant and warm oil, with immediate lubrication, instead of struggling through a cold start at −15°C.
Diesel heaters are susceptible to carbon buildup if operated continuously at low output. Deposits accumulate around the glow plug and inside the burner chamber. At least once per month, run the diesel heater at full output for 30 minutes — the higher combustion temperature burns away deposits and can extend the life of both the burner and glow plug by several years.
Most Common Mistakes
- Mixing blue-green and pink G13 coolant. They can gel together, blocking the heating circuit and leading to expensive repairs.
- Skipping coolant replacement. Blue-green coolant has a two-year service life — not five. Once depleted, it attacks aluminium components.
- Ignoring gurgling noises. Air does not disappear on its own. The system must be actively bled.
- Running the diesel heater at minimum output all season. Without occasional high-power operation, carbon deposits build up and damage the burner and glow plug.
- Relying solely on propane abroad. Cylinder connections and refill systems differ by country. A diesel backup provides true independence.
- Not knowing where the bleed valves are. Locate and mark them before winter arrives — they are much harder to find when working outside in freezing temperatures.
Frequently Asked Questions
How long does it take for a hydronic system to warm up after arrival?
Expect 45–180 minutes, depending on the outdoor temperature, how well the motorhome is insulated, and how cold the vehicle has become during parking. At −5°C with a well-insulated vehicle that was warm when parked, 45–60 minutes is realistic. After a cold overnight at −15°C with the heating off, allow 2–3 hours before the interior reaches full comfort. This is the fundamental trade-off of hydronic heating versus forced-air — and the reason the engine heat exchanger is so valuable: if the Alde system has been running while driving, the interior is already warm on arrival.
Can I install an Alde Compact together with a Webasto or Eberspächer diesel heater?
Yes — and it is the ideal configuration for year-round, multi-country travel. The Webasto Thermo Top (or Eberspächer Hydronic) connects directly to the Alde coolant circuit as a parallel heat source. Both systems heat the same fluid, so convectors, underfloor heating, and domestic hot water all function normally regardless of which heat source is active. The Alde controller continues to manage circulation and temperature. Switchover between gas and diesel backup is typically manual, though some integrations allow automatic failover. The additional benefit of the Webasto is engine preheating before cold starts.
How can I tell if my hydronic system contains trapped air?
Three reliable indicators: (1) Gurgling or trickling sounds from inside the convectors — this is the most obvious sign. (2) One area of the motorhome stays cold while others heat normally — the convector in that area has an air pocket blocking coolant flow. (3) The circulation pump is running but coolant level in the expansion tank is dropping — air is compressing and coolant is being drawn in to fill the gap. If you suspect air, run the pump at maximum speed (setting 5) for 10 minutes and listen for changes in the gurgling pattern, then bleed the system at the highest bleed points.
How do I tell whether my system contains blue-green or pink G13 coolant?
The simplest method is to look inside the expansion tank. Blue-green (ethylene glycol, older specification) is distinctly green or blue-green. Pink/magenta G13 (OAT technology, modern Alde Magenta) is clearly pink or light purple. If the coolant appears brownish, discoloured, or cloudy, it has likely exceeded its service life and should be replaced regardless of type. If you are unsure of the history, check the service records or ask the motorhome's previous owner. When in doubt — replace the coolant completely rather than top up with the wrong type.
Do I need to drain the hydronic circuit when storing the motorhome over winter?
Not if the coolant is correctly mixed to the right concentration. A 50:50 mix of Premium G13 and distilled water protects down to approximately −35°C — sufficient for virtually all European storage conditions. Verify the concentration with an antifreeze hydrometer or refractometer before storage. If the concentration is correct, simply close the gas cylinder valve, switch off the Alde system, and leave the coolant in the circuit. Draining is only necessary if the motorhome is stored in conditions where temperatures could drop below the coolant's freeze point, or if the coolant is due for replacement.
How much propane does an Alde heating system consume on a typical winter night?
With the gas burner as the sole heat source: at outdoor temperatures around −5°C in a well-insulated motorhome, expect approximately 0.3–0.6 kg of propane per night (assuming 6–8 hours of moderate heating). At −15°C, this rises to 0.8–1.2 kg/night. If connected to shore power with the 3 kW electric element active, propane consumption can be zero. Using the engine heat exchanger during the drive significantly pre-heats the coolant mass, reducing the amount of gas needed after arrival. These figures vary considerably depending on insulation quality, thermostat set-point, and how well the vehicle seals against draughts.
Related articles
- Air Conditioning in a Motorhome — the heat pump mode of an inverter air conditioner as a supplemental heat source in spring and autumn.
- Charging LiFePO₄ While Driving — how the Iveco engine simultaneously charges batteries and heats the living area via the heat exchanger.
- Inverters and Inverter/Chargers — PowerControl for limiting shore power current when the Alde electric element and other appliances run simultaneously.