The Finned-Tube Coil - Short #269
HVAC School - For Techs, By Techs
Bryan Orr
4.9 • 1K Ratings
🗓️ 9 December 2025
⏱️ 13 minutes
🧾️ Download transcript
Summary
In this short podcast episode, Bryan explores the history of the finned-tube coil, which is what we use for heat exchange in air-source air conditioners and heat pumps.
Air-source HVAC systems have copper tubes threaded through thin metal fins. This design was optimized to ensure the greatest possible surface area for heat exchange to occur. However, prior to the finned-tube coil, HVAC coils looked more like plumbing projects with bare copper loops, which were heavy, costly, and inefficient.
In the early 1900s, HVAC was essentially plumbing with higher expectations; capacity was dictated purely by size and charge. In the 1910s and 1920s, early air conditioning pioneers were already attempting to increase surface area with metal discs or pipes, which evolved to continuous sheet fins. The tube would move refrigerant, and the fins would collect heat from the air and pass it into the tube; the finned-tube coil was born. The added weight was minimal, but the contact area was increased by almost 3000%, meaning coils and charges could be smaller with added efficiency.
This move was necessary because while we already knew that heat can indeed move without touching molecules (radiant transfer), radiant cooling had a unique challenge: dew point. Finned-tube coils rely on convection and only have temperatures below the dew point in a small area, which allows us to have a small drain pan. Aluminum was also plentiful after WWII, enabling finned-tube technology to evolve to louvered fins and reach the masses. By the 1960s, finned-tube coils were in all sorts of applications. However, it became clear that aluminum was fragile, and we have since innovated to overcome that challenge.
There are three barriers that heat transfer must overcome: air-side film resistance (air is a poor conductor), wall conduction through the tube and fins, and refrigerant-side film resistance (oil inside or laminar flow). The fins help with air-side film resistance, so we want to clean and straighten them as much as possible.
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Transcript
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| 0:00.0 | Hello, this is the HVAC school podcast. I'm Brian. This is the podcast that helps you remember some things you might have forgotten along the way, as well as helps you remember some things you forgot to know in the first place. And today we're talking about the fin-tubed coil and the history therein or thereof or however you say that. But before we do that, |
| 0:21.9 | we want to thank our great brand partners. Carrier and Carrier.com. Carrier has been a long-term |
| 0:28.3 | sponsor of the podcast. They've made it possible very early on for us to do what we do, and they are |
| 0:33.6 | the products that we sell day in and day out, everything from single stage equipment |
| 0:37.5 | all the way up to the green speed extreme, one of the most efficient products on the market |
| 0:43.0 | today. Find out more about what Carrier has to offer and about becoming a carrier dealer |
| 0:47.7 | by going to Carrier.com. |
| 0:51.2 | Refrigeration Technologies at refrigetec.com. |
| 0:55.4 | Field piece in the Cat 85 Combustion Analyzer. |
| 0:59.3 | Cat 85 measures everything you need to keep your customers safe, O2, CO, CO2, and draft pressure. |
| 1:06.3 | It comes with a built-in monometer, so you have one less tool to carry and can knock out static and gas pressure readings in one fell swoop. |
| 1:14.9 | The real interesting thing about the CAD-85 is its sensor technology for better accuracy, longevity, and ease of use. |
| 1:21.7 | It automatically separates and returns accumulated water to the flu using the patent-pending hydrocycle pump technology. You know who |
| 1:29.8 | needs hydrocycle pump technology? Why, all of us? Sensors are field-replaceable, so you don't |
| 1:34.5 | have to wait on shipping timelines and can just change it right then and there to maximize uptime, |
| 1:39.2 | as well as patent-pending sensor vault technology, prolonging sensor life. |
| 1:45.9 | Sensors also come with a four-year warranty. |
| 1:51.5 | As with a lot of other FieldPiece tools, you can connect the Cat-85 with the JobLink System app to get all your readings in one place, and there's a 1,000-foot wireless range. |
| 1:56.7 | Find out more at FieldPiece.com, and be sure to check out the Cat 85 and the other handy combustion |
| 2:02.3 | analyzers and add-ons. That's fieldpiece.com. Don't miss the biggest annual North American |
| 2:09.7 | HVACR trade event in 2026, the AHR Expo, February 2nd through the 4th at the Las Vegas Convention Center, in Las Vegas, of course. |
| 2:20.4 | Whereas our symposium is a relatively tight-knit event, the AHR Expo is a huge event. It's huge. It's |
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