{"product_id":"diesel-water-heater-12kw","title":"12KW Diesel Water Heater 12V — Apollo-C3 Coolant Heater for Trucks, RVs, Caravans and Boats","description":"\u003cstyle\u003e\n.c3-wrap{font-size:16px;line-height:1.7}\n.c3-wrap h2{margin:32px 0 12px;font-size:24px;line-height:1.3}\n.c3-wrap h3{margin:22px 0 8px;font-size:19px;line-height:1.35}\n.c3-wrap p{margin:0 0 14px}\n.c3-wrap ul{margin:0 0 16px 20px}\n.c3-wrap li{margin-bottom:7px}\n.c3-spec{width:100%;border-collapse:collapse;margin:16px 0;font-size:15px}\n.c3-spec th,.c3-spec td{border:1px solid #d8d8d8;padding:9px 12px;text-align:left;vertical-align:top}\n.c3-spec th{background:#f4f4f4;width:38%;font-weight:600}\n.c3-fit{width:100%;border-collapse:collapse;margin:16px 0;font-size:15px}\n.c3-fit th,.c3-fit td{border:1px solid #d8d8d8;padding:9px 12px;text-align:left;vertical-align:top}\n.c3-fit th{background:#f4f4f4;font-weight:600}\n.c3-note{border-left:4px solid #c8102e;background:#fbf4f5;padding:12px 16px;margin:18px 0}\n.c3-cta{background:#f4f4f4;padding:18px 20px;margin:26px 0;text-align:center}\n\u003c\/style\u003e\n\n\u003cdiv class=\"c3-wrap\"\u003e\n\n\u003ch2\u003eOne Heater, Two Jobs: Engine Preheat and Cabin Heat\u003c\/h2\u003e\n\n\u003cp\u003e\u003cstrong\u003eThe Apollo-C3 is a 12KW diesel water heater that warms your engine coolant and your cab at the same time, with the engine switched off.\u003c\/strong\u003e It burns diesel from the tank you already have and circulates hot coolant through the engine block and your existing heater core.\u003c\/p\u003e\n\n\u003cp\u003eYou get a warm cab before you climb in, and an engine that turns over like it is a mild autumn morning. No idling, no extension cord, no shore power.\u003c\/p\u003e\n\n\u003cp\u003eThe economics are simple. A heavy diesel engine burns \u003cstrong\u003e0.8–1.0 gallons per hour\u003c\/strong\u003e just sitting there making heat. A fuel-fired coolant heater does the same job on a small fraction of that, because it heats the coolant loop instead of spinning an entire engine.\u003c\/p\u003e\n\n\u003cp\u003eThere is a legal side too. More than 30 US states cap how long you may idle, with fines running from \u003cstrong\u003e$100 to $25,000\u003c\/strong\u003e. Cold-weather exemptions usually apply only when you have no other way to make heat — so the heater is what keeps you both warm and compliant.\u003c\/p\u003e\n\n\u003cp\u003eTruck, bus, coach, boat, car, caravan or generator set: if it runs a large diesel with a coolant loop, the Apollo-C3 installs the same way.\u003c\/p\u003e\n\n\u003ch2\u003eWhat 12KW Actually Buys You\u003c\/h2\u003e\n\n\u003cp\u003e\u003cstrong\u003e12KW is roughly 40,900 BTU per hour delivered into a coolant loop.\u003c\/strong\u003e That is truck, bus, boat and generator territory, not van territory.\u003c\/p\u003e\n\n\u003cp\u003eOne thing to sort out before you buy: search results for a 12 kW diesel heater mix two completely different machines. A 12KW \u003cem\u003ewater\u003c\/em\u003e heater and a 12KW \u003cem\u003eair\u003c\/em\u003e heater do not do the same job.\u003c\/p\u003e\n\n\u003cp\u003eIf you are shopping for a 12KW diesel heater to blow hot air straight into a living space, this is not that product — look at a \u003ca href=\"https:\/\/www.rvheater.com\/products\/diesel-air-heater\"\u003ediesel air heater\u003c\/a\u003e instead. This one plumbs into a coolant circuit.\u003c\/p\u003e\n\n\u003cp\u003eThat extra step is what lets one burner preheat your engine, defrost your windshield through the vents you already have, and warm the cab. You will also see this class of unit sold as a liquid parking heater or a night heater — same machine, different name.\u003c\/p\u003e\n\n\u003ch2\u003eIs the Apollo-C3 the Right Size for Your Vehicle?\u003c\/h2\u003e\n\n\u003cp\u003e\u003cstrong\u003eBuy the C3 if you are heating a large diesel engine or a big coolant loop. Buy something smaller if you are heating a van or a camper.\u003c\/strong\u003e\u003c\/p\u003e\n\n\u003cp\u003eOversizing a coolant heater is a real problem, not a theoretical one. A heater with more output than the loop can absorb reaches its setpoint fast, shuts down, and restarts — over and over. That short-cycling is hard on the glow pin and encourages carbon buildup in the burner.\u003c\/p\u003e\n\n\u003ctable class=\"c3-fit\"\u003e\n\u003ctr\u003e\n\u003cth\u003eYour setup\u003c\/th\u003e\n\u003cth\u003eWhat to get\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eHeavy truck, bus, coach, tractor, marine engine, generator set\u003c\/td\u003e\n\u003ctd\u003e\n\u003cstrong\u003eApollo-C3 — 12KW\u003c\/strong\u003e (this page)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCampervan, caravan, motorhome, pickup, small boat\u003c\/td\u003e\n\u003ctd\u003e\u003ca href=\"https:\/\/www.rvheater.com\/products\/diesel-water-heater\"\u003eApollo-C1 diesel water heater — 5KW\u003c\/a\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eYou only want warm air in a living space, no engine preheat\u003c\/td\u003e\n\u003ctd\u003e\u003ca href=\"https:\/\/www.rvheater.com\/products\/diesel-air-heater\"\u003eDiesel air heater — 2.5KW or 5KW\u003c\/a\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eYou park where there is mains power every night\u003c\/td\u003e\n\u003ctd\u003e\u003ca href=\"https:\/\/www.rvheater.com\/products\/truck-engine-block-heater-titan-p3\"\u003eTitan-P3 electric engine block heater\u003c\/a\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/table\u003e\n\n\u003cp class=\"c3-note\"\u003e\u003cstrong\u003eNot sure which side of that line you fall on?\u003c\/strong\u003e Send us your engine displacement and coolant capacity at \u003ca href=\"mailto:info@vvkb.com?subject=Apollo-C3%2012KW%20Sizing%20Check\"\u003einfo@vvkb.com\u003c\/a\u003e and we will tell you honestly whether the C3 or the 5KW C1 is the better fit. We would rather talk you down a size than take a return.\u003c\/p\u003e\n\n\u003ch2\u003eSpecifications\u003c\/h2\u003e\n\n\u003ctable class=\"c3-spec\"\u003e\n\u003ctr\u003e\n\u003cth\u003eModel\u003c\/th\u003e\n\u003ctd\u003eApollo-C3\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eType\u003c\/th\u003e\n\u003ctd\u003eDiesel water heater \/ coolant heater (hydronic)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eHeat output\u003c\/th\u003e\n\u003ctd\u003e12KW — approx. 40,900 BTU\/hr\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eFuel\u003c\/th\u003e\n\u003ctd\u003eDiesel (also runs on winter and arctic grade)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eVoltage\u003c\/th\u003e\n\u003ctd\u003e12V DC\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eOperating temperature\u003c\/th\u003e\n\u003ctd\u003e-40°F to 140°F (-40°C to 60°C)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eDimensions\u003c\/th\u003e\n\u003ctd\u003e14.2 × 4.9 × 7.1 in (360 × 125 × 180 mm)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eShipping weight\u003c\/th\u003e\n\u003ctd\u003e26.5 lb (12 kg)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eWarranty\u003c\/th\u003e\n\u003ctd\u003e1 year, extendable\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eShips from\u003c\/th\u003e\n\u003ctd\u003eUS, Canada, Europe or Australia warehouse\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/table\u003e\n\n\u003ch2\u003eFuel Supply: The One Thing That Causes Most Failures\u003c\/h2\u003e\n\n\u003cp\u003e\u003cstrong\u003eDo not tap the heater into your vehicle's existing fuel line. Fit a dedicated standpipe into the tank.\u003c\/strong\u003e This single decision separates the installs that run for years from the ones that fight air locks every cold morning.\u003c\/p\u003e\n\n\u003cp\u003eThe reason is the metering pump. It moves a very small amount of fuel per stroke, and it cannot clear an air bubble the way an engine lift pump can. Tapped into a return line or a shared feed, it loses prime, fails to light, and locks out after three attempts.\u003c\/p\u003e\n\n\u003cp\u003eA standpipe drops straight into the tank with its own pickup, so the heater always draws clean fuel from its own point. Fitting one takes an afternoon and a careful hole.\u003c\/p\u003e\n\n\u003cul\u003e\n\u003cli\u003e\n\u003ca href=\"https:\/\/www.rvheater.com\/products\/heater-fuel-stand-pipe\"\u003eFuel standpipe\u003c\/a\u003e — the part that prevents the problem above\u003c\/li\u003e\n\u003cli\u003e\n\u003ca href=\"https:\/\/www.rvheater.com\/products\/vvkb-fuel-pump-for-webasto-diesel-heater-12v-24v-air-parking-diesel-truck-boat-bus-caravan\"\u003eMetering fuel pump\u003c\/a\u003e — spare, 12V and 24V\u003c\/li\u003e\n\u003cli\u003e\n\u003ca href=\"https:\/\/www.rvheater.com\/products\/diesel-heater-glow-plug\"\u003eKyocera ceramic glow plug\u003c\/a\u003e — the wear part on any diesel heater\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eTwo more fuel rules worth following. Switch the heater off before you refuel, and after you change to winter or arctic diesel, run it about \u003cstrong\u003e15 minutes\u003c\/strong\u003e so the line fills with the new fuel.\u003c\/p\u003e\n\n\u003ch2\u003ePlumbing the Coolant Loop\u003c\/h2\u003e\n\n\u003cp\u003e\u003cstrong\u003ePlumb the C3 across your coolant loop, not in series with a single hose.\u003c\/strong\u003e The most common first-draft mistake is drawing it inline in a way that starves the circuit.\u003c\/p\u003e\n\n\u003cp\u003eThree rules that decide whether your install self-bleeds or gives you an air pocket:\u003c\/p\u003e\n\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eRoute hoses upward toward the heater\u003c\/strong\u003e so trapped air can rise out on its own.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eNever point the coolant inlet and outlet fittings downward.\u003c\/strong\u003e Air collects there and stays.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eKeep the coolant line to a rear-mounted heater below the highest point of the loop\u003c\/strong\u003e, or it will hold a bubble you cannot chase out.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eFit the heater ahead of your heat exchanger inlet where you can. Start the first run with the coolant below \u003cstrong\u003e86°F (30°C)\u003c\/strong\u003e.\u003c\/p\u003e\n\n\u003cp class=\"c3-note\"\u003e\u003cstrong\u003eSetpoint tip:\u003c\/strong\u003e holding the loop around \u003cstrong\u003e167°F (75°C)\u003c\/strong\u003e keeps the engine thermostat closed, so your heat stays in the block and cab instead of going out through the radiator.\u003c\/p\u003e\n\n\u003ch3\u003eExhaust and Air Intake\u003c\/h3\u003e\n\n\u003cp\u003eThe exhaust must terminate outside the vehicle, pointing down or up to 20° rearward, and never into the direction of travel. Keep the outlet at least \u003cstrong\u003e0.8 in (20 mm)\u003c\/strong\u003e away from brake lines, wiring and anything else heat-sensitive.\u003c\/p\u003e\n\n\u003cp\u003eRun the \u003ca href=\"https:\/\/www.rvheater.com\/products\/free-shipping-air-exhaust-muffler-for-webasto-heater-parking-heater-2kw-2-5kw-5kw\"\u003eexhaust muffler\u003c\/a\u003e at least \u003cstrong\u003e7.9 in (200 mm)\u003c\/strong\u003e from the heater body. It is not optional equipment.\u003c\/p\u003e\n\n\u003ch2\u003eBuying a Chinese-Built Coolant Heater Without Getting Burned\u003c\/h2\u003e\n\n\u003cp\u003e\u003cstrong\u003eYes, the internals of this class of heater are broadly similar across brands. What is not similar is who is still there in year three.\u003c\/strong\u003e We would rather say that plainly than pretend otherwise.\u003c\/p\u003e\n\n\u003cp\u003eVvkb has been in business since 1996 and building diesel heaters in China since 2003. We watched this category go from a handful of workshops to hundreds of competing suppliers, and we know exactly which parts get swapped for cheaper ones when someone needs to hit a price.\u003c\/p\u003e\n\n\u003cp\u003eWhat you are actually paying for here:\u003c\/p\u003e\n\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eParts you can still buy in three years\u003c\/strong\u003e — glow plugs, fuel pumps, mufflers and standpipes are stocked and listed, not discontinued.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eA 1-year warranty you can extend\u003c\/strong\u003e, handled by the people who built the unit rather than a reseller.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eStock in four regions\u003c\/strong\u003e — US, Canada, Europe and Australia — so it ships without a six-week wait.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eReal answers by email\u003c\/strong\u003e, including the ones that talk you out of this model and into a smaller one.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eMaintenance That Actually Matters\u003c\/h2\u003e\n\n\u003cp\u003e\u003cstrong\u003eRun the heater once a month, even in July.\u003c\/strong\u003e A burner that sits unused all summer is the single most common reason a unit will not light in November.\u003c\/p\u003e\n\n\u003cp\u003eBeyond that, the list is short. Check the exhaust outlet is clear before the first cold snap. Replace the fuel filter on your normal service interval. Inspect the glow pin if start times get longer than usual.\u003c\/p\u003e\n\n\u003cp class=\"c3-note\"\u003e\u003cstrong\u003eFit a carbon monoxide alarm in any space where people sleep.\u003c\/strong\u003e The C3 keeps combustion sealed and vents exhaust outside the vehicle, and a working CO alarm is still non-negotiable. Clamps, seals and correct routing reduce risk — they do not replace a detector.\u003c\/p\u003e\n\n\u003ch2\u003eFrequently Asked Questions\u003c\/h2\u003e\n\n\u003ch3\u003eCan I tap the heater into the existing fuel line on my truck?\u003c\/h3\u003e\n\n\u003cp\u003e\u003cstrong\u003eYou can, and it is the number one source of problems.\u003c\/strong\u003e The metering pump on any diesel heater moves a tiny volume per stroke and cannot push past an air bubble. Tapped into a return line or shared feed, it loses prime, fails to ignite, and locks out after three attempts. Fit a dedicated standpipe into the tank instead. It gives the heater its own pickup point and clean fuel every start.\u003c\/p\u003e\n\n\u003ch3\u003eIs 12KW too much heater for a van or camper?\u003c\/h3\u003e\n\n\u003cp\u003e\u003cstrong\u003eAlmost certainly yes.\u003c\/strong\u003e The Apollo-C3 is sized for heavy trucks, buses, marine engines and generator sets. On a small coolant loop it hits setpoint quickly, shuts off, and restarts repeatedly. That short-cycling is hard on the glow pin and builds carbon in the burner. For a campervan, caravan, motorhome or pickup, the 5KW Apollo-C1 is the correct choice and costs less.\u003c\/p\u003e\n\n\u003ch3\u003eCan I use the Apollo-C3 to heat shower water?\u003c\/h3\u003e\n\n\u003cp\u003e\u003cstrong\u003eNot directly, and never by running potable water through it.\u003c\/strong\u003e People searching for a diesel hot water heater often land here, so it is worth being clear. The Apollo-C3 heats a closed coolant loop and holds it at a setpoint. It is not a tankless water heater and does not modulate for shower temperature. If you want domestic hot water, run the coolant loop through a calorifier or a marine water heater with a built-in coolant heat exchanger, and take the hot water from that tank.\u003c\/p\u003e\n\n\u003ch3\u003eHow much current does it draw from my battery?\u003c\/h3\u003e\n\n\u003cp\u003e\u003cstrong\u003eMost current is drawn in the first two to three minutes, while the glow pin is energized.\u003c\/strong\u003e Once combustion is stable the glow pin switches off and draw falls sharply, leaving the circulation pump and combustion fan running. If your only power source is a single starter battery and you park for short periods, add a dedicated battery or plan to drive afterward. Cold weather increases startup demand.\u003c\/p\u003e\n\n\u003ch3\u003eDo I need a carbon monoxide alarm?\u003c\/h3\u003e\n\n\u003cp\u003e\u003cstrong\u003eYes. Fit one in any space where people sleep.\u003c\/strong\u003e The combustion chamber is sealed and exhaust vents outside the vehicle, so cabin air and exhaust never mix in a correct installation. A CO alarm is what tells you when an installation stops being correct, such as a cracked pipe, a loose clamp, or a blocked outlet. Exhaust clamps and seals are not a substitute for a detector.\u003c\/p\u003e\n\n\u003ch3\u003eWill it still start after sitting all summer?\u003c\/h3\u003e\n\n\u003cp\u003e\u003cstrong\u003eIt will if you run it monthly.\u003c\/strong\u003e Ten minutes once a month keeps the fuel line wet, clears the burner, and confirms the glow pin still works while it is still warm enough to fix. Units that sit from March to November are the ones that fail on the first cold morning.\u003c\/p\u003e\n\n\u003ch3\u003eCan I install it myself?\u003c\/h3\u003e\n\n\u003cp\u003e\u003cstrong\u003eYes, if you are comfortable cutting into a coolant circuit and drilling a fuel tank.\u003c\/strong\u003e Budget a full day. The three jobs that decide whether it works are the standpipe, plumbing across the loop rather than in series, and an exhaust that exits outside pointing down or rearward. If any of those make you uneasy, have a diesel shop do the install.\u003c\/p\u003e\n\n\u003ch3\u003eWhat warranty comes with it, and can I get parts later?\u003c\/h3\u003e\n\n\u003cp\u003e\u003cstrong\u003eOne year as standard, extendable, handled directly by the people who built it.\u003c\/strong\u003e Glow plugs, metering fuel pumps, exhaust mufflers and standpipes are all stocked as separate items, so a wear part does not turn into a dead heater. Units ship from our US, Canada, Europe or Australia warehouse.\u003c\/p\u003e\n\n\u003cdiv class=\"c3-cta\"\u003e\n\u003cp\u003e\u003cstrong\u003eReady to stop idling for heat?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eThe Apollo-C3 12KW diesel water heater ships free from a regional warehouse with a 1-year warranty.\u003c\/p\u003e\n\u003cp\u003eStill deciding between 12KW and 5KW? Email \u003ca href=\"mailto:info@vvkb.com?subject=Apollo-C3%2012KW%20Sizing%20Check\"\u003einfo@vvkb.com\u003c\/a\u003e with your engine size and coolant capacity, and we will tell you which one to buy.\u003c\/p\u003e\n\u003cp\u003e\u003ca href=\"https:\/\/www.rvheater.com\/collections\/vvkb-hydronic-coolant-heater\"\u003e\u003cstrong\u003eSEE ALL COOLANT HEATERS →\u003c\/strong\u003e\u003c\/a\u003e\u003c\/p\u003e\n\u003c\/div\u003e\n\n\u003c\/div\u003e\n","brand":"vvkb","offers":[{"title":"12V","offer_id":37190432267,"sku":"","price":928.56,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/1623\/1847\/files\/Vvkb12KWDieselEngineHeaterApollo-C3.jpg?v=1715846991","url":"https:\/\/www.rvheater.com\/products\/diesel-water-heater-12kw","provider":"Vvkb","version":"1.0","type":"link"}