Quiet Heat

by Bob Livingston
November 29, 2013
Filed under Gear, Gear Reviews, RV News


Swedish company, Alde, introduces a convection and radiant comfort heating system (with hot water) to North America


With the onset of winter, motorhome enthusiasts will rely on their furnaces to keep the interiors cozy. The most common heat source is a forced air furnace that uses a combustion chamber and a blower to distribute warm air through strategically placed registers. Higher-end coaches may be equipped with a hydronic system like the Aqua-Hot, which uses tubing to route heated liquid to heat exchangers that are located throughout the interior. Advantages of a hydronic system include relatively quiet operation, good energy efficiency, balanced heat distribution and an integrated hot water provision, eliminating the need for a separate appliance.

The well-designed Compact 3010 hydronic system can be serviced easily using  simple hand tools. Here, the combustion fan is removed with little effort.

The well-designed Compact 3010 hydronic system can be serviced easily using
simple hand tools. Here, the combustion fan is removed with little effort.

A new company on the scene in America, Alde, uses a different approach to hydronic heating in a motorhome: silent convection and radiant heat produced by a boiler that operates on LP-gas or 120-volt AC power. The Alde system uses a network of convectors that are located on the interior walls; air warmed by the convectors flows up the walls and around the furniture to heat the interior while forming a barrier in front of the windows that prevents the cold air from entering the coach. Once this warm air reaches the ceiling, it circulates to the floor where it is reheated by the convectors. The result is warm, even heat that has a soothing effect on residents, without annoying fan noise.
Alde’s heating system may be new to the U.S., but it’s a staple in the European motorhome industry, with a number of trailer (caravan) builders also electing to install the hydronic system on higher line models. The Swedish company was founded in 1949 and started out manufacturing products for cars and tractors. By 1966 it built its first central heating system and today is a major — and well-respected — supplier to the European RV industry.
The heart of the Alde hydronic system is a compact boiler that can be mounted under a dinette or other suitable compartment inside the coach. Across the pond, limited space and tight dimensions are the norm, so the company has developed a finely crafted, compact boiler that heats the liquid and pumps the fluid to con­vectors and radiator panels, resulting in uniform interior warmth using the science of convection currents. An easy access coolant reservoir is tied into the boiler and the heated liquid is distributed through a system of tubing that leads to the convectors and panels. Additional pipe loops with diffusion plates are integrated into the floor to offer radiant heating.
Flat panel radiators are used in restricted spaces — such as bathrooms and wardrobes — where it would be difficult to mount normal convectors. In order for the warm air to move freely via convection, the hardware is placed using pinpoint precision and the system must be custom designed for individual floorplans. Alde engineers take an active role with RV designers, analyzing each floorplan and providing recommended convector locations. This requires placing cabinets and furniture so that a small space is allocated for the air to circulate. In many cases, the interior must be reconfigured to accommodate the heating system. This precise integration of components results in even heating throughout the coach with almost no cold spots, an outcome that can’t be matched by traditional forced air furnaces.
To test the efficiency of this system, I was invited to participate in an extreme cold weather test. A prototype motorhome was placed inside a cold locker where the temperature was monitored at minus 22 F. Thermocouples were carefully placed throughout the interior and temperatures were recorded on digital instrumentation. The company was developing a system for this particular coach, so the evaluation was a work in progress.


Systems installed in motorhomes are controlled by a color touch screen (3.5 inches), which has navigation menus for information, settings and tools.


Rolled edges and precision welding are two attributes of the inner boiler wall assembly. Each component is closely inspected during manufacturing.


Heating elements that operate on 120-volt AC power are installed on the inner wall of the boiler. Antifreeze is heated inside this chamber.


The entire tank assembly is pressure- tested for leaks using a machine that holds it underwater for a period of time. Every tank is subjected to this test.


The heat exchanger is pressure-tested during the welding process. Each step goes through rigid quality control inspections.


A machine rotates the unit during precision welding where robotics ensure each piece holds tight tolerances.


Boiler tank is wrapped in Styrofoam to control temperature and heat loss of the exterior housing. Gas valve assembly is to the left of the boiler in this orientation.


Expansion tank is usually mounted above and near the boiler housing. The system is required to use nontoxic antifreeze in order to meet U.S. manufacturing standards.


Every unit is bench tested and given a serial number corresponding to recorded results, which are used to provide support for installers and end users.


Circuit board and connections are easily serviceable via an access plate. Test procedures can be performed without removing the boiler housing.


A fully operational network of piping, convectors and radiators allows technicians to test existing and newly developed products. Testing results are recorded using accurate digital instrumentation.


Aluminum convectors are constructed using a tube that’s surrounded by evenly spaced fins. The convectors are available in a number of lengths and configurations.


System efficiency during installation prototyping is checked using a heat gun. Screen graphics show whether or not temperature is consistent with control setting.


Heated towel railing is a nice touch to any motorhome bathroom when traveling in cold country.


The more exotic towel radiator is a high performance unit with an adjustable thermostat.


A motorhome is tested in a cold locker that reduces outside temperature to minus 22. Frozen water is a good visual that confirms extreme outside temperature.

Upon entering the motorhome, it was immediately evident that the interior was quite comfortable, which was remarkable considering the “outside” temperature. I took off my shoes to check out the floor and the comfort level was heavenly. Heat guns were used to validate heat distribution and locate cold spots. One cold spot was discovered behind the seat adjacent to the entry door and Alde engineers were using that data to relocate convectors before presenting the final blueprint to the motorhome manufacturer. The rest of the interior — including areas in front of the windows — was consistent with the temperature set on the digital control center. This type of engineering prowess and manufacturing support is refreshing and the results speak for themselves.
The boiler also produces hot water for the bathroom and galley and can be set to produce only hot water in summer when comfort heating is not needed. Capacity for the standard system is somewhat limited at this time (about 4 gallons of mixed warm water), but optional components are available that can expand capacity, and will likely be used by U.S. builders.
There are a number of other features that can be tied into the Alde system that enhance its operation. On the creature comfort side, a heated towel bar can be incorporated into the pipe loop, a luxury used more commonly in Europe. To increase driver comfort, a specially designed convector can be installed to boost heat in the cab and a fan-driven heat booster (convector with small fans connected in series) can be strategically placed to rapidly heat areas like, for example, the cockpit or wardrobes and/or compartments where wet clothing may be stored.
Also, the system can be equipped with a heat exchanger that circulates engine coolant through the tubes, reducing the consumption of LP-gas while on the road. Heat can also be directed into the holding tank area to prevent the contents from freezing in cold weather. If the RV is stored in cold weather, a safety valve will automatically open, draining the system and preventing freeze damage.
After spending time with Alde engineers, I was given the opportunity to dismantle a boiler to experience serviceability. The process is relatively intuitive using simple hand tools; access to the electronics and components for diagnostic purposes is provided without removing the boiler. I was immediately impressed with the finish quality of the boiler and the fact that technicians won’t have to wear Kevlar gloves to prevent cuts when handling the components and housing.
Operation of the Alde hydronic system requires a different mindset. Owners familiar with fan/heat cycling and the temperature fluctuations that go with typical forced air furnace function will enjoy the even temperature afforded by the Alde. But, it takes about four hours to get the rig up to temperature (from storage) and stabilize the desired heat level based on control panel settings. This is a completely new paradigm (think preplanning) for the majority of North American RVers, who typically click on the thermostat when reaching their destination or heading out on the road after the coach has been in storage.
One of the first North American adopters is Canadian manufacturer Roadtrek. It’s using the Alde system in the CS-Adventurous, a Sprinter-based Class B motorhome (see page 45). The inherent benefits of a heating system with integrated hot water are even more dramatic in a small coach where space for appliances and suitable locations for bulky ducting and registers is at a premium.
Alde’s hydronic system raises the bar when it comes to efficient RV comfort heating technology and makes it practical to travel in cold weather without shivering and listening to furnace cycling. Alde is experienced in building heating systems for RVs used in the cold north, which makes it uniquely qualified to be a new supplier to the U.S. RV industry.
Alde | www.alde.se/usa

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