The Ultimate Guide to Diesel Heaters for Campervans: Stay Warm Off-Grid

Staying warm turns “endure” into “enjoy.” A well-installed diesel air heater keeps your van cosy, dries condensation, and sips both power and fuel, perfect for British winters and damp shoulder seasons. This UK-specific guide covers safety, sizing, installation principles, troubleshooting and seasonal tips.

There’s nothing more morale-boosting than stepping into a warm, dry van after a day in the British drizzle. A properly installed diesel heater for campervan turns endure into enjoy: it dries kit, drives away condensation, and sips both fuel and battery power. This guide is UK-specific, plain-English, and safety-first. It covers how heaters work, what size to choose, real-world power/fuel use, installation principles, noise and smell fixes, troubleshooting, and ready-to-buy kit bundles.

Safety first (read this bit)

• Sealed combustion only. Diesel air heaters draw combustion air from outside and exhaust outside via a stainless pipe. Inside the van, a separate clean airstream passes over a heat-exchanger. The two streams never mix.

• CO alarm + smoke alarm. Fit a BS EN 50291 carbon-monoxide alarm and a smoke alarm; test every month.

• Wiring & fusing. Provide a dedicated, fused 12 V supply direct from your leisure battery or distribution bus. Keep voltage drop under ~3 % at 12 V (typical cable 2.5–4 mm² for common run lengths; check your heater manual).

• Fuel take-off. Use the vehicle’s auxiliary pickup or a proper standpipe. Don’t T-piece into return lines unless the vehicle manufacturer explicitly allows it.

• Exhaust & intake. Stainless exhaust sloping downwards with a silencer; combustion intake with a silencer/filter. Terminate well away from doors, windows, vents, or any LPG locker outlet. Use heat shields near anything heat-sensitive.

• Paperwork. Prefer units with E-marking and UNECE R122 (heating) and R10 (EMC) compliance. Buy from reputable sellers that supply manuals, parts and support.

• Know your limits. Cutting the floor and routing an exhaust is not a first-ever DIY job. If in doubt, use a professional who knows leisure vehicles.

How diesel air heaters work

A low-power metering pump feeds tiny pulses of diesel into a burn chamber. A glow plug lights the fuel; the chamber heats a sealed heat-exchanger. A separate fan moves cabin air across that exchanger and out through ducts. The controller modulates output from low to high, so the heater can tick over quietly or ramp up to warm the shell fast.

Why they’re ideal for UK vans

• Dry heat fights damp and condensation.

• Low electrical draw compared to electric heating.

• Works whether you’re on a campsite or wild-camping.

What size heater do I need? (2 kW vs 5 kW)

• 2 kW (e.g., Webasto Air Top 2000 STC, Eberspächer/Espar D2/S2, Autoterm/Planar 2D): best for small/medium vans and well-insulated LWB builds with modest duct runs. Quieter, thriftier, and happiest running in the middle of its range.

• 5 kW: for large LWB/H3 vans, long duct splits (front + rear), sparse insulation, or very cold camping. Louder and more prone to sooting if idled on “low” for long periods.

Rule of thumb: Insulate properly and pick 2 kW unless your interior volume/ducting genuinely needs 5 kW. A right-sized heater spends more time in the clean, efficient mid-range.

Real-world power and fuel use (UK numbers)

Electrical (12 V)

• Start/glow: 8–10 A for 1–3 minutes.

• Running: about 0.8–1.2 A (2 kW on low) to 2–3 A (2 kW high / 5 kW mid).

• Overnight (8 h): typically 8–20 Ah. A 100 Ah LiFePO₄ bank handles several cold nights without stress.

Fuel

• 2 kW: roughly 0.10–0.24 L/h (low → high).

• 5 kW: roughly 0.12–0.50 L/h (low → high).

• A 10 L day tank comfortably covers a chilly long weekend at moderate output.

Installation principles (overview, not a step-by-step)

• Location. Under a seat box is common; underfloor cradles work if weather-proofed. Keep ducts short and smooth with gentle bends (60 mm duct for 2 kW; 75 mm for 5 kW).

• Through-floor. Cut a clean aperture, treat bare metal against rust, use the supplied mounting plate and gasket, and seal for water ingress.

• Combustion path. Stainless exhaust with a downward fall and a silencer; intake with silencer/filter. Use heat shields where the exhaust approaches anything vulnerable.

• Fuel system. Use the OEM aux pickup or a standpipe. Mount the metering pump close to the tank, at ~15–35° inclination on a rubber isolation mount to reduce the “tick”. Use the supplied hard nylon microline and an inline filter; avoid kinks and long unsupported spans.

• Electrics. Dedicated fused feed (often 10–15 A fuse) and controller wiring per the manual. Size cable to minimise voltage drop; poor supply is the number 1 cause of failed starts and lock-outs.

• Controls. Basic rotary, digital thermostat, or brand “smart” controller. Keep any temperature sensor out of direct heat or sun.

Noise, smell and condensation: quick wins

• Pump ticking. Rubber-isolate the pump and clip both fuel line and loom to stop panel drumming.

• Fan whine / airflow hiss. Use decent ducting, gentle bends, and avoid crushed flexi hose. Closeable vents help balance flow.

• Diesel smell outside. Check exhaust joints and slope; keep the outlet clear of spray and away from any opening.

• Condensation. Diesel air heat is dry. Crack a window and run the heater on high for 10 minutes to purge moisture and dry kit.

Altitude, winter diesel and maintenance

• Altitude. Air is thinner at height; rich mixtures soot. Premium heaters include altitude compensation. Some budget units offer a controller “CO₂ offset”. If you’ll camp above ~1,500–2,500 m, choose a heater with proper support.

• Fuel in winter. UK forecourts switch to winter-grade diesel seasonally. If you use a separate day tank, fill with winter diesel before a cold snap. Only use blends/additives the manufacturer permits.

• Keep it clean. Give the heater an Italian tune-up (10–15 min on full power) weekly in the colder months. Inspect the glow-plug screen, intake/exhaust clamps and ducts each season.

Worked bundles (small van → full-timer)

Below are complete shopping lists, lists assume you already have a leisure battery and basic 12 V distribution.

A) Small van / weekender (quiet & frugal)

• 2 kW premium heater kit (Webasto / Eberspächer / Autoterm 2D)

• Fuel pickup: standpipe or OEM adapter

• Inline fuel filter + pump isolation mount

• Stainless exhaust + silencer

• Combustion intake silencer + filter

• 60 mm ducting + 1–2 outlets

• CO alarm

• Electrics: 12 V blade fuse holder, 10–15 A fuses, correctly sized cable, grommets, heat-shrink

B) LWB / family tourer (two outlets, mild winter)

• 2 kW premium or 5 kW budget 

• Y-piece + extra outlet

• Duct insulation 

• Underfloor mounting plate

• Noise kit:

• Ducting + 1–2 outlets

• CO alarm

• Electrics: 12 V blade fuse holder, 10–15 A fuses, correctly sized cable, grommets, heat-shrink

C) Full-timer / alpine-curious (quiet + altitude support)

• Premium 5 kW with altitude mode/compensation

• Programmable controller / thermostat

• Upgraded stainless exhaust, heat shields/wrap

• 10 L diesel day tank

• Service spares

• CO + smoke alarm

• 2 kg dry-powder extinguisher

• Electrics: 12 V blade fuse holder, 10–15 A fuses, correctly sized cable, grommets, heat-shrink

Recommended parts

Premium heaters (E-marked / R122)

• Webasto Air Top 2000 STC (2 kW)

• Eberspächer/Espar Airtronic S2 D2L (~2.2 kW)

  
  

Budget kits (12 V)

• 2 kW/5 kW” complete kit with controller

Ducting & outlets

• 60 mm duct kit

• 75 mm duct kit

• Y-piece & closeable vents

Combustion & noise control

• Stainless exhaust + silencer

• Intake silencer + filter

• Pump isolation mounts

Fuel system

• Standpipe or OEM pickup adapter

• Inline micro fuel filter

• Hard nylon microline + clips

• 10 L day tank

Electrics & installables

• 12 V fuse gear & cable

• Hole saw set (60–75 mm) & step drill

• Heat shield / exhaust wrap

• Sealant

• Rust treatment

• Grommets

Safety

• CO alarm

• Smoke alarm

• 2 kg dry-powder fire extinguisher

Troubleshooting (fast fixes that actually work)

Won’t start / keeps flaming out

• Low voltage at the heater. Thicker cable, shorter run, clean terminals; check the fuse.

• Restrictions in intake/exhaust or a kinked fuel line. Clear and re-prime.

• Sooted burn chamber from days on “low”. Run on full power for 15 minutes.

Loud ticking (fuel pump)

• Re-mount on a rubber isolation block and clip fuel line firmly. Avoid bolting directly to resonant panels.

Diesel smell

• Outside: leaky exhaust joint or poor slope. Reseat clamps, maintain a downward fall.

• Inside: very rare on reputable units; check ducts near the exchanger and stop the heater if you suspect a combustion leak.

Overheating / shutdown

• Blocked outlet, crushed duct, or recirculating hot air. Open the flow, smooth bends, move the temperature sensor.

Altitude sooting

• Enable altitude mode/CO₂ offset if available. Without it, avoid long periods at high altitude.

Diesel Heater For Campervan FAQs

Is it safe to run a diesel heater overnight? Yes, when correctly installed (sealed combustion), maintained, and with a working CO alarm. Many owners run them all night.

Can I tap the van’s main fuel tank? Yes. Use the vehicle’s auxiliary pickup or a standpipe. Avoid T-pieces on returns unless the OEM says it’s acceptable.

What battery bank do I need? A 100 Ah LiFePO₄ bank comfortably covers typical overnight use (8–20 Ah). Larger banks help in deep winter.

Does a 5 kW unit burn five times the fuel of a 2 kW? No. On low, consumption is similar; on high a 5 kW can be roughly ~2× a 2 kW. Size your system so you operate mid-range most of the time.

Can I mount the heater under the van? Yes, with a weather-proof cradle and protected ducting, but servicing is harder. Many people fit them under a seat box inside for easy access.

Seasonal tips for the UK

Summer & shoulder seasons

• Ten minutes on high dries wetsuits, muddy boots and bedding.

• Draw intake air from a cooler area; avoid sucking from a hot locker.

Winter

• Expect longer runtimes; budget fuel accordingly.

• Protect lithium batteries from charging below 0 °C (heater draw is fine; charging is the issue).

• If you run a separate day tank, fill with winter-grade diesel before a cold spell.

All year

• Ventilate: a roof vent plus a cracked window helps purge moisture.

• Give the heater a weekly full-power burn to stay clean.

Thanks — and please share

If this guide helped you get your heating plan sorted, share it in your favourite UK vanlife group or send it to a mate who’s mid-build. It really helps others stay safe and warm. Got questions or a tricky install? Drop them in the comments and we’ll try to help. Stay toasty and travel well! 🔥🚐🇬🇧