The ESI install manual for a 5 kW diesel air heater — to ABYC, not the box pamphlet. The parts & how it works, mounting, combustion air, the marine exhaust (high & aft, wrapped), fuel & dosing pump, ducting, the no-kill-switch electrical, the three controllers & priming, commissioning with the break-in & CO test, and hydronic for boats over 40′.
Before you start
The ESI install manual for a 5 kW diesel air heater — done to ABYC, not the box pamphlet. The parts and how it works, mounting, combustion air, the marine exhaust (mounted high & aft, wrapped — not ‘downhill’), fuel & the dosing pump, ducting, the no-kill-switch electrical, the three controllers and priming, commissioning with the break-in and CO test, hydronic for boats over 40′, and a component testing & fault-finding reference. ABYC alerts throughout; a final exam unlocks your certificate.
Stainless, double-wrapped, mounted high, aft of the cockpit. No downhill.
Off at the controller — it must complete its shutdown cycle.
Three controllers; sea-level altitude; it idles, doesn't shut off.
Chapter 1
A diesel heater is a fuel + exhaust + CO system, not a plug-in.
These 5 kW “Chinese diesel” air heaters are clones of the Webasto / Eberspächer parking heater: a metered diesel mist burns in a sealed chamber, a fan blows cabin air across the heat exchanger, and the exhaust vents overboard. To standard they're safe and excellent; off the box pamphlet they're a CO hazard. We install them to ABYC.
| Standard | Covers |
|---|---|
| ABYC A-7-2021 | Boat heating systems — combustion air, exhaust, clearances, fuel, controls. |
| ABYC A-24-2025 | Carbon-monoxide detection — a marine CO alarm where people sleep. |
| ABYC H-33-2021 | Diesel fuel systems — pickup, line, connections. |
| ABYC E-11-2025 | The DC wiring — fused, sized, supported. |
Chapter 2
Know the parts and you diagnose instead of guess.
One small burner, one fan, two air paths. The fan drives combustion air into the chamber and cabin air across the outside of the heat exchanger at the same time. The diesel never touches the cabin air.
| Part | What it does |
|---|---|
| Glow plug | Silicon-nitride ceramic igniter — heats fast to light the fuel mist on start-up (and during low burn). A wear item (M8/M10/M12). |
| Burner screen / gauze | Wicks and vaporizes the metered fuel in the chamber for a clean burn. Carbons up over time — a service item. |
| Combustion chamber | High-temp 2520 stainless can where the fuel burns. |
| Metering orifice / dosing pump | The pump delivers a fixed tiny dose (~0.02 mL) per pulse; the pulse rate (Hz) sets the burn. A 5 kW uses roughly 0.16–0.52 L/h. |
| Heat exchanger, fins & case | The finned body the burner heats inside and the fan cools outside — the air shroud / case ducts cabin air across the fins. |
| Blower fan | One motor drives both the combustion-air impeller and the heating-air fan. |
| Fuel filter | Inline — protects the pump and orifice from grit/water. |
Chapter 3
Solid, accessible, ports clear.
The heater body sits inside (a locker, lazarette, under a settee); its intake, exhaust and fuel ports pass through the mounting plate.
Chapter 4
Clean outside air in — never cabin air.
The heater pulls a small amount of combustion air through its own ~25 mm intake hose — separate from the cabin air. The manufacturer ships a set length: keep it that length, unblocked, and don't shorten or extend it (it's tuned to the burner).
Chapter 5
The highest-stakes run. Forget ‘downhill’.
On a vessel this size you almost never get a downhill exhaust run — and you don't try. Marine diesel-heater exhaust is built to run up to a high outlet, double-walled and wrapped, terminating where fumes can't blow back aboard.
Chapter 6
Clean diesel, metered, and a quiet pump.
The heater sips fuel — the dosing pump meters it (Chapter 2). Two things make or break the fuel side: a clean pickup, and a properly mounted pump.
Chapter 7
Move the heat; recirculate where you can.
Separate from combustion air, the heater pulls heating (cabin) air across the heat exchanger and blows it back warm.
It is preferred to provide a cabin recirculation airflow — draw the heating-air intake from the cabin and return it warm; that's the most efficient and warms the boat fastest. Where a cabin recirc pickup isn't practical, draw fresh outside air instead — but recirculate when you can.
Chapter 8
Fused, sized — and NEVER on a kill switch.
A 5 kW heater pulls a big surge at start-up (the glow plug) then little while running. The wiring is easy; the control philosophy is the part people get dangerously wrong.
When you turn a diesel heater off, it runs a shutdown / post-purge cycle: the burner stops but the fan keeps running to cool the chamber and burn off the glow plug. This takes a couple of minutes.
Chapter 9
The common controls — set up, programmed, and primed.
For all the rebadging, these ship with only a handful of controller families. They are not interchangeable and the menus differ — verify against the unit — but the logic is shared. Below is the initial setup, programming and priming for each.
1 · Rotary knob + LCD — the simplest.
2 · Multi-button LCD panel (+ remote) — the most common.
3 · 3-button LCD — a cut-down version of #2.
4 · Bluetooth / app — phone-controlled (e.g. Vevor).
Controller setup & priming compiled from the common rotary-knob, multi-button LCD (incl. the 1688 advanced menu and H-on prime), 3-button and Bluetooth/app units (VEVOR, rvheater, general LCD-panel manuals). Always confirm the exact buttons against the switch manual for the controller installed.
Chapter 10
Prove it safe — and warn about the first hour.
The install isn't done until it's proven safe — and the owner is told what the first run looks like.
Chapter 11
When air ducting isn't enough — the coolant system.
The single most important reason to step up to hydronic isn't boat length on its own — it's that an air heater is practically limited to about two warm-air outlets. Split the air duct more than that and you choke the airflow, drop the temperature at each register, and trip the over-temp lockout. So once a boat needs heat in more than two places — roughly over 40 feet, multiple cabins, or where you also want domestic hot water — the air heater runs out of outlets and we fit a hydronic (coolant) diesel heater. The marine standard is Webasto Hydronic / Thermo Top (Eberspächer Hydronic is the equivalent). Work from their manuals.
The diesel burner heats a coolant (water/glycol) loop instead of air — like a small engine. A circulation pump drives that hot coolant around the boat to fan-matrix heat exchangers in each cabin (each with its own blower and thermostat), to a calorifier (hot-water tank) for domestic hot water, and it can pre-warm the engine. One burner, many zones, through small coolant hoses instead of big air ducts.
| Component | Role |
|---|---|
| Hydronic heater (burner) | Burns diesel to heat the coolant loop (its own combustion air + exhaust like the air heater). |
| Circulation pump | Pumps the hot coolant around the loop. |
| Fan-matrix heat exchangers | One per cabin/zone — a small radiator + blower + thermostat that puts the heat into the cabin. |
| Calorifier | Hot-water tank heated off the loop (and usually a shore-power immersion element too). |
| Expansion tank, drain & bleeds | The sealed-loop bits — fill, bleed out air, and an exhaust condensation drain + silencer. |
Chapter 12
Test the part, replace the part — not the whole heater.
When a heater won't light, smokes, or shuts down, work it like any system: watch the start-up sequence to find the area, then meter the suspect. Almost every fault is the glow plug, the fan, the fuel side, or a sensor — and each has a number you can check.
On a normal start, in order, you should see and hear: the temp / overheat sensor check, the glow plug energize (it pulls roughly ~8 A), the fan spin up slowly, the chamber heat, the fan speed up, then the dosing pump start ticking and the burner light. Where the sequence stalls tells you where to test.
| Component | How to test | Pass / spec |
|---|---|---|
| Glow plug | Power off, disconnect it, meter (Ω) across the two terminals. Inspect for cracks / heavy carbon. | ~0.6–1.2 Ω. OL/open or > ~6 Ω = failed. Draws ~8 A when energized. |
| Fan / blower motor | Power off, spin the impeller by hand. Check it clears the housing. | Must spin free — no rub, no rough/notchy bearing, no drag. A dragging motor over-draws current and trips the heater. |
| Fuel dosing pump | Meter the coil (Ω) across its terminals. Listen for a steady tick when commanded. Output test: prime into a measuring cup and count pulses. | ~8–12 Ω. OL = burnt winding; ~0 Ω = shorted. ~0.02 mL/pulse (verify by model). |
| Overheat / flame / temp sensors | Meter for continuity / resistance per the unit. | An open overheat sensor or a failed flame sensor will stop the start — replace. |
| Burner screen / gauze | Pull and inspect. | Heavy carbon = hard starting & sooting. Clean or replace; confirm the glow plug seats and the screen is in place. |
| Combustion chamber | Visual. | Cracked or warped = condemn — it can leak exhaust into the cabin air. |
| Fuel filter & line | Inspect / blow through. | Clear, no water or air. A clogged filter starves the pump and mimics a pump fault. |
| Wiring / connectors / voltage | Meter battery voltage at the unit during the glow-plug surge. | Clean, tight, full voltage under load. Low voltage looks exactly like a dead glow plug. |
| Symptom | Likely cause | Check first |
|---|---|---|
| Won't light, no fuel tick | Pump, filter/air, no fuel | Pump Ω (8–12), filter, fuel level, prime |
| Glow-plug fault / no glow | Glow plug or low voltage | Glow plug Ω (0.6–1.2), leads, voltage at unit |
| White smoke then dies | Unburnt fuel — weak glow / rich / carbon | Glow plug, burner screen, restricted exhaust |
| Black smoke / sooting | Too much fuel for the air | Hz too high, choked intake/ducting, carbon screen |
| Shuts down hot (over-temp) | Choked air side or dragging fan | Recirc/ducting restriction, spin the fan, sensor |
| Rough / loud fan, won't spin up | Worn motor bearing | Spin-free test → replace the motor |
Test values: glow plug ~0.6–1.2 Ω (fail >6 Ω / OL); dosing-pump coil ~8–12 Ω (OL = open, ~0 = short); glow-plug draw ~8 A; fan must spin free — per common Eberspächer/Webasto and Chinese-heater service data. Confirm against the unit's manual where given.
Chapter 13
How we work is part of the work. This applies to every job.
Skill gets the job right; discipline gets it done profitably and hands the customer a boat that's better than we found it. These habits run through every ESI field job.
Before you walk to the boat, plan the job and gather the tools, parts and equipment you'll need. Think it through end to end and stage it. A planned job is a fast job; a forgotten tool is a trip you didn't have to make.
Use a cart for each job. Stage your tools, parts and consumables on it so everything travels with you to the boat and stays in one place — not scattered, and not back in the shop.
Every trip back to the shop is unbillable time the customer doesn't pay for and the job eats. Walking costs money. Keep your tools organized and within reach so you're working, not searching or fetching.
Count the extra trips you make to the shop and record those numbers. Trips per job, tracked over time, show where pre-planning is slipping and where we can tighten up. Honest numbers, every job.
No job is done until it's to spec, cleaned, and inspected by the lead. Leaving the engine room or cockpit dirtier than we found it is never acceptable.
ESI runs on Kaizen — continuous improvement. Small better-ways found on the boat, captured every day, compound into a faster, sharper shop. That only works if you write it down.
Field reference
Field-tested: the symptom, the usual cause, and the fix. Always diagnose before you replace parts.
| Symptom | Likely cause | Fix |
|---|---|---|
| Won’t light / error on first run | Air in the fuel line, a weak glow plug, or low supply voltage | Re-prime, test glow-plug resistance (≈0.6–1.2Ω), confirm >11–12 V at the unit |
| Heavy smoke at start-up | Normal exhaust-wrap break-in, or over-fuel / wrong altitude | If it persists: set altitude to sea level for ocean, check intake & exhaust for restriction |
| Shuts down with a fault mid-run | Over-temp from a blocked outlet, flame-out, or low voltage | Clear the outlet/return air, check the fuel pickup, confirm battery voltage under load |
| Sooting / coking up | Wrong altitude setting or a restricted exhaust | Set sea-level altitude for ocean use; clean the burn chamber, screen and exhaust |
| Loud ticking dosing pump | Pump hard-mounted to the structure | Re-mount on a rubber/suspension bracket, outlet angled up |
| No fuel reaching the unit | Blocked tank pickup, air, or a weak pump | Check the standpipe, re-prime, test the pump-coil resistance |
| Fumes / CO concern | Exhaust leak or an unsealed penetration | Seal and run the exhaust high & aft, re-check the penetration, test the CO alarm |
Final certification
A short check ran at the end of each chapter. Pass this final at 80% to unlock your certificate.