I Turned a Diesel Heater Into a Condensing Boiler… and Got 95% Efficiency!

Video Description

Last week, I pushed HLN’s 20kW diesel hydronic heater through a brutal 100-gallon torture test, and it delivered 19.4 kW at 71% efficiency — the most efficient stock hydronic heater I’ve ever tested. But during that test, one thing kept nagging at me: The exhaust was HOT. Really hot. Enough heat to warm a room on its own. So today I’m doing something nobody recommends (including HLN)… Using a 3-inch air-to-water intercooler to scavenge exhaust heat from a diesel heater. The goal? Turn a 71% efficient heater into a near-condensing boiler. Did we break it? Did it work? Let’s find out. IT IS NOW AVAILABLE ON THE WEBSITE! https://www.hlnind-shop.com/products/hln-aquano-12k-coolant-heater-24v 🎁 HLN Heaters are expensive, Ive asked them for some help on the price. here is a Discount Code: Use %Jasonhurst for 20% off. — and support the channel at the same time. The air to water intercooler - https://amzn.to/3XlSDpJ These are affiliate links and support the channel if you use them. ⸻ 🔧 TEST SETUP • HLN 20 kW diesel hydronic heater (24V) • 3” large-core air-to-water intercooler • 10-gallon and 100-gallon water loads • Fuel measured by precision scale • Exhaust routed directly into the intercooler • Cold water hits the intercooler before the heater This is NOT how you would install a real system — this is strictly a proof of concept experiment. ⸻ 🧪 RESULTS — 10 Gallon Test • Start temp: 8.2°C • End temp: 75.5°C • Time: 8:49 • Fuel used: 284.8 g • Output: 17.2 kW • Efficiency: 74% Good, but the thermal mass was too small to tell us much. So… I ran the big one. ⸻ 🧪 RESULTS — 100 Gallon Intercooler Test • Start temp: 17.8°C • End temp: 61.3°C • Time: 45:43 • Fuel used: 2 liters And here’s where it gets wild: • Output: 25.1 kW • BTU/hr: 85,700 • Efficiency: 95% Yes — ninety-five percent!! The intercooler pulled so much heat out of the exhaust that the vapor actually condensed into liquid water, turning the system into a condensing boiler for most of the test. This was not a fluke — the numbers check out, and the fuel/lift data backs every bit of it. ⸻ ⚠️ BUT… There Are Consequences This system works incredibly well, but comes with major risks: • Condensate is acidic (carbonic acid) • Moisture inside the intercooler can lead to corrosion • If soot ever builds up → mud + acid + heat = failure • Potential freezing issues if water isn’t evaporated each cycle • Likely requires regular flushing and maintenance • Absolutely not recommended by HLN This is not a set-and-forget upgrade. This is an experiment. ⸻ 💭 Would I Use This in My Own Rig? As a secondary or supplemental heat system? Maybe. It’s fascinating and legitimately increases performance. As a primary heat source? Probably not — too many maintenance risks. Still, as a proof-of-concept: This worked WAY better than I expected. Want more info? see all the math on my blog post https://hangingwiththehursts.com/reviews/dieselcondensingboiler ⸻ 💬 Transparency & how to get one HLN sent me this heater to test, but: • This is not a paid review • HLN has no control over what I say • All opinions and test results are my own, and I stand by the math IT IS NOW AVAILABLE ON THE WEBSITE! https://www.hlnind-shop.com/products/hln-aquano-12k-coolant-heater-24v 🎁 HLN Heaters are expensive, Ive asked them for some help on the price. here is a Discount Code: Use %Jasonhurst for 20% off. — and support the channel at the same time. 👉 Contact Kevin at HLN: Tell him you saw Jason’s 20kW test and what you’re trying to heat. He can help spec a system for your application. [email protected] Use code %JasonHurst at checkout to save 20% on any HLN product at: https://www.hlnind-shop.com/collections/diesel-heater-water-heater He can spec a unit for your cabin, shop, bus, or off-grid setup. ⸻ 🙏 Thanks for Watching If you made it to the end of this video, you’re my kind of person. I love doing weird, deep-dive heater experiments like this — so if you want to see more: 👍 Hit Like 💬 Drop your questions 🔔 Subscribe so you don’t miss the next build See you in the next one. – Jason