Official installation guidance for HLN Aerolyn 2kW / 4kW diesel air heaters — mounting, fuel line, combustion air, exhaust and hot-air ducting rules, from the manufacturer's installation manual.

⚠️ Safety first: fuel and exhaust work must be done with the heater off and cooled down. Exhaust must always terminate outside the vehicle. If in doubt, ask us before improvising.

Hot Air Outlet Duct — Max Length 6 ft (2 m), First Vent Must Stay Open

For Aerolyn air heaters (2kW/4kW/8kW): the HOT AIR OUTLET tube must be 6 ft (2 m) or LESS in total length. If your ducting system is longer, the FIRST vent/outlet of the ducting must be located within 6 ft (2 m) of the heater, and that first vent must ALWAYS remain OPEN (never close or block it). Restricted or overly long outlet ducting causes back-pressure and heat build-up: the heater may overheat, trigger high-temperature shutdown (error codes), or shorten component life. Rule of thumb: short, straight, smooth duct runs; first outlet within 2 m; keep it open at all times.

Install Where Heat Can Escape — Enclosed Boxes Cause Overheating

The mounting location must let heat dissipate. Do NOT install the heater inside a small sealed box or closed cabinet: the heater re-breathes its own hot air and the case cannot shed heat, causing heat build-up, high-temperature shutdowns, and shortened component life. If a compartment installation is required, the compartment must have ventilation openings so cabin air can reach the heater intake and case heat can escape — and keep at least 50 mm clearance from bulkheads. A heater that runs then shuts down with a high-temperature fault, especially at higher power levels, is very often an enclosed-install problem.

Heater Installation Location Requirements

The heater should be installed in a protective cover or compartment. The location must: keep the heater away from strong shock or wading risk; provide a flat horizontal surface; and allow for connections of fuel line, combustion air intake, exhaust, electrical components, and ducting.

Possible Mounting Locations by Vehicle Type

In a truck: at the foot of the auxiliary seat, on the rear cab wall, under the driver's seat, or in the toolbox. In a recreational vehicle: on the lower left side of the driver's seat. In a van: under the rear seat. In a construction vehicle: in the protective case.

Mounting Plate and Hole Drilling Procedure

A mounting plate is included in the installation kit. Select a proper location, then drill and cut holes per the installation hole diagram for the combustion inlet, exhaust outlet, and fuel intake. Mount the heater on the mounting plate using the provided nuts and bolts.

Fuel System Installation Specifications

The fuel can be drawn directly from the vehicle tank via an independent pipeline. If the tank is more than 10 m away, use a separate fuel tank. The height difference between fuel surface and heater must not exceed ±500 mm. Use Φ4×1 nylon pipe with a dedicated joint, tighten the tubing clamp, and use protective casing. Mount the electromagnetic pump with the pressure side rising upward at 15°–35° angle. Tubing from pump to tank must be ≤1 m; tubing from pump to heater must be ≤9 m.

Electromagnetic Fuel Pump Angle Requirement

The electromagnetic pump must be installed with the pressure side rising upwards at an angle of at least 15°. An installation angle between 15° and 35° is preferable.

Combustion Air Inlet Hose Rules

Fasten the combustion air inlet hose to the heater with a pipe clip. The hose must be 0.2 m to 2 m long and lead to fresh air outside the vehicle. Turning angle must be no less than 90°. The air inlet must not directly face the direction of vehicle movement, must not allow exhaust gas entry, and must have no blocking objects within 300 mm below.

Exhaust Pipe Installation Requirements

Fasten the flexible exhaust pipe with a pipe clip. The turning angle must be no less than 90° to prevent exhaust gas from entering the air inlet or vehicle windows. The exhaust outlet must end in open air, must not face the direction of vehicle movement, and must not exceed the vehicle's side limit. Maintain clearance around the pipe, keep no obstructions within 300 mm below, and ensure snow or other objects cannot block the pipe end.

300 mm Clearance Below the Exhaust Outlet

No obstruction shall be allowed within 300 mm below the exhaust-gas outlet of the heater. The exhaust-gas outlet temperature is high and can ignite non-heat-resistant materials such as wire harness, rubber pipeline, and hydraulic pipeline.

Indoor Installations Must Vent All Exhaust Outside

If the heater is installed indoors, all waste gas must be led to the outside and no leakage is allowed. Failure to do so may result in the risk of exhaust poisoning or suffocation.

Combustion Air Must Come From a Clean Area

Make sure that heating air comes from an area free of poisonous gas.

Cabin Air Inlet Pipe Notes

The heater air inlet should draw circulating air from the cabin. If the pipe is too long or makes sudden turns, air volume will reduce, causing high heater body temperature and automatic shutdown. If no air inlet pipe is installed, the heater must be at least 50 mm from the bulkhead to ensure sufficient air intake.

Hot Air Outlet Pipe Installation

Fasten a corrugated aluminum pipe with a clamp at the hot air outlet and lead the pipe into the cabin for heating and defrosting. If the pipe is too long or makes sudden turns, air volume will reduce, causing high heater body temperature and automatic shutdown.

Switch Panel Cutout Dimensions

The installation size for the standard operating panel is 84 mm × 44 mm (some controller models use a 44 mm × 55 mm opening — check the template supplied with your controller).

Wire Harness Connection Order

One end of the control harness connects to the switch or switch transition lines, another end connects to the heater, and the last end connects the heater to the electromagnetic pump.

Fuel Quantity Test Procedure

Preparation: (1) Detach the fuel line from the heater. (2) Insert the fuel line into a 100 ml graduated cylinder. (3) Switch the heater ON to bleed air from the fuel system. (4) Switch the heater OFF and empty the graduated cylinder. Measurement: (5) Switch the heater ON. (6) Wait 5 minutes for the heater to reach full power. (7) Run for exactly 300 seconds (5 minutes), then switch OFF. (8) Record the fuel collected.

Pre-Start Safety Checks Before First Ignition

Before starting the heater, check whether the fuel duct and circuit connections are correct, whether the air inlet and outlet pipe and exhaust pipe are arranged normally, and whether there is any foreign body entry. No inflammable or explosive goods should be placed near the heater.

Annual Maintenance Check

When using the heater for the first time each year, check the heater status to ensure smooth air inlet and outlet, and smooth combustion air inlet and exhaust. Clean these passages if necessary and check for any abnormal operation.

Hydronic (Coolant) Heaters: Orientation and Antifreeze

The HLN Aquano hydronic heater must be installed horizontally, within ±5° of level, in an area free from vibration. If installed outside the cabin, a shroud above the heater is recommended. Antifreeze solution must be rated for the local ambient temperature — unsuitable antifreeze may freeze and stop circulating. When replacing coolant, remove the discharge plug and completely bleed air from the circulatory system before refilling.

Minimum AC Power Supply Wattage

When powering the heater from AC mains, a stabilized voltage power supply of more than 400 W is recommended. The power supply must exceed the heater's ignition power consumption, or the heater may not work normally.

Do Not Drag the Heater by the Wire Harness

Do not move the heater by dragging the harness.

Installation kits and parts: fuel pump, WiFi controller.

About HLN — For 50+ years HLN has built diesel air and hydronic heaters as original equipment for major truck, bus and RV manufacturers (YuTong, SANY, XCMG and two Fortune-500 truck makers), with CE / ECE R122 / R10 certification. Shop the heaters this guide covers: Aerolyn 2kW, Aerolyn 4kW, Aquano 5K hydronic. Questions? Email kevin@hlnind.com — real engineers answer.