Espar Heater Installation

The Espar Airtronic S3 D2L is the single most popular heater in the van conversion industry — and for good reason. Designed specifically for the diesel platform, the D2L taps directly into your Sprinter's factory fuel tank, drawing a fraction of a gallon per hour to produce reliable, thermostat-controlled cabin heat in any condition. From a sub-zero night in the Colorado Rockies to a damp November morning on the Oregon coast, the D2L delivers consistent warmth without touching your battery bank or requiring you to carry a separate fuel source.

The S3 generation represents Espar's latest engineering — quieter combustion, improved fuel atomization, and a more refined startup sequence that reduces the brief smoke puff older models were known for. The integrated controller allows you to set a target temperature and let the heater manage itself, cycling between low and high output to maintain your comfort level without overshooting. At low output, the D2L is virtually inaudible inside the cabin. At full output, it produces enough heat to keep a Sprinter's interior comfortable when it's well below freezing outside.

This is the heater we install on Mercedes Sprinter builds more than any other. The diesel fuel system integration is clean and straightforward on the Sprinter platform — our team has routed hundreds of these fuel pickups and knows exactly where to tap the line, how to route the exhaust, and where to position the unit for optimal heat distribution and minimal noise transmission into the living space.

Not every van runs on diesel. The Ford Transit and Ram ProMaster — two of the most popular platforms in the van conversion world — are gasoline-powered vehicles. The Espar Airtronic S3 B2L brings the same German-engineered, fuel-fired heating performance to gasoline platforms that the D2L delivers on diesel. Same sealed combustion. Same whisper-quiet operation. Same programmable thermostat. Same negligible electrical draw. The only difference is the fuel it burns.

The B2L taps into your Transit's or ProMaster's gasoline fuel system, drawing fuel directly from the tank your engine already uses. There's no separate fuel canister to fill, no propane tank to swap, and no electric element draining your batteries. You pull into a gas station, fill your van like you normally would, and you've just refueled your heating system too. On a full tank, the B2L provides enough fuel for weeks of overnight heating — the fuel consumption at low output is measured in fractions of a gallon per hour.

For Ford Transit and Ram ProMaster owners, the B2L is the correct choice — not because it's better or worse than the D2L, but because it's engineered for the fuel your van carries. Gasoline combustion has different characteristics than diesel, and the B2L's burner assembly, fuel pump, and control logic are all tuned specifically for gasoline atomization and ignition. Installing a diesel heater on a gasoline van (which some shops attempt with a separate diesel tank) creates unnecessary complexity, adds weight, and introduces a second fuel type you have to manage. The B2L eliminates all of that.

The Espar Hydronic takes a fundamentally different approach to heating your van. Instead of blowing heated air directly into the cabin like the Airtronic models, the Hydronic heats your vehicle's engine coolant — the same fluid that circulates through your engine block and factory heating system. This creates two benefits in one unit: cabin warmth through the factory heater core and engine preheating that makes cold-morning starts dramatically easier on your drivetrain.

For van owners who spend time in genuinely cold climates — the kind of cold where your engine oil turns to molasses overnight and your diesel fuel starts to gel — the Hydronic is a dual-purpose investment. Set it on a timer to warm the coolant thirty minutes before your alarm goes off, and you wake up to a warm cabin and an engine that starts like it's been idling all night. No cold-start wear. No waiting for the engine to warm up. No scraping ice off the inside of your windshield. The Hydronic turns a bitter-cold morning into a non-event.

The Hydronic integrates with your vehicle's existing coolant loop, which means cabin heating is distributed through the factory vents rather than a single point source. This creates more even heat distribution throughout the van and allows the system to leverage the factory blower motor and ductwork that's already built into the vehicle. For builds where even heat distribution matters — or where the dual benefit of cabin heat plus engine preheating justifies the additional installation complexity — the Hydronic is the premium choice in the Espar lineup.

A heater by itself is a component. A heater integrated with ventilation, insulation, and air circulation is a climate system. At OZK, we don't just bolt an Espar under the van and hand you the keys — we design the heater installation as part of your van's complete climate architecture. The ducting route, the thermostat placement, the heat outlet positioning — all of it is planned to work with your interior layout, your insulation package, and your ventilation system.

The Espar pairs naturally with a MaxxAir fan for air circulation. The heater produces warm air; the MaxxAir moves it. On a cold night, the fan running on low intake pulls fresh air into the van while the Espar keeps the temperature stable — giving you both warmth and ventilation without opening a window and losing heat. In shoulder-season weather, the MaxxAir alone handles the climate. In summer, an AC unit takes over. The Espar handles winter. Together, they cover every month of the year.

Because the Espar draws less than one amp of electrical power, it has virtually no impact on your battery bank — leaving your full electrical capacity available for lighting, refrigeration, water pumps, and electronics. This is the integration advantage of fuel-fired heating: it operates on a completely independent energy source from the rest of your van's systems. Your solar panels and lithium batteries power your life. Your fuel tank powers your heat. No competition, no compromise, no cold nights because you ran the heater too long and killed the batteries.