5.5 Alde Heating System and Coolant Replacement ServiceAlde Heating System and Coolant Replacement Service The Alde wet heating system, commonly installed in caravans and motorhomes, offers a high level of comfort by operating similarly to a household central heating system. Instead of blown air, it circulates a specific heating fluid throughout the system, which heats your space and provides hot water. Many owners prefer this system due to its quiet operation, consistent warmth, and energy efficiency.