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One of the trends he’s not happy about at all is condensing coils that are made from aluminum (aluminum tube/aluminum fin). He notes that copper tubes with aluminum fins, which are the usual choice for condensing coils, are superior to aluminum because of copper’s superior strength, reliability, ease of maintenance, and excellent heat transfer characteristics.
Much to Forty’s dismay, some manufacturers continue to use aluminum for their condensing coils. He notes that two of the biggest problems are that aluminum coils are more difficult to maintain and almost impossible to repair in the field — which is why he’d like to see copper condensing coils made by every manufacturer.
ALUMINUM GETS A FOOT IN THE DOORThe aluminum tube/aluminum fin condensing coil first came about in the 1970s. General Electric was in the hvac business at the time, and had built an air conditioning system that used an aluminum condensing coil. “GE was the only company that did that. All the other manufacturers used copper tube with aluminum fins bonded to it. The indoor evaporative coil was always copper with aluminum fins,” explains Forty.
Prior to 1980, probably 80% of the homes didn’t have air conditioning; the equipment was expensive and many considered it to be a luxury they couldn’t afford. According to Forty, the market shifted in the Chicago area around 1980 to a busy add-on market for air conditioning systems caused by a tremendous building boom. Inflation was rampant then, and people’s homes were drastically increasing in value.
There was a difference, however, between the GE coil and the other manufacturers’. “The new aluminum coils were pretty cheap. GE had a real heavy-duty aluminum condensing coil,” says Forty. GE subsequently got out of the hvac business, while other manufacturers continued to produce the aluminum tube/aluminum fin condensing coil. And that’s where we are today.
SOME DRAWBACKSForty says that one of the biggest problems with aluminum is that leaks can occur where the aluminum meets the copper in the condensing unit due to galvanic action. “What started to happen in the mid-80s is the condensing unit started to leak where the copper tube and the aluminum tube met. It leaked and you couldn’t fix it. It was not repairable,” states Forty.
Leaks can still be a problem, even though manufacturers have used improved equipment so that oxygen doesn’t reach the condensing coil to cause the galvanic action.
“If somebody pokes a hole in an aluminum tube, you can’t easily fix it. You have to use a special fitting, and you have to cut out the bad part and put some kind of fitting in between there, and that’s a lot of rigmarole. Because of the time involved in the process, it’s not done very often. We’ve never done it. And if it’s inside five years, you get a new coil from the factory anyhow. If it’s after five years, it doesn’t make sense to fix it because usually it’s so clogged full of dirt, you just trash the unit and start over. It’s disposable,” says Forty.
Mike Williams, an applications engineer with LRC Coil, Santa Fe Springs, CA, notes that the inability to repair an aluminum tube condensing coil in the field can be a big problem. “You could have a leak in an aluminum-tubed coil and the average contractor cannot repair it. They don’t have a welding rig, and welding aluminum, particularly thin aluminum, is tricky. You can hit a brazing torch to a copper tube and you can fix it.”
Ken Kaye, sales and engineering manager for Super Radiator Coils, Phoenix (AZ) Division, notes that while his company occasionally manufactures an aluminum tube/aluminum fin condensing coil, it’s usually only for special applications. “Some of the larger residential companies have gone to aluminum tube/aluminum fins because of cost and weight. We don’t really recommend that,” he says.
“When we make aluminum coils here, we actually weld the joints. A lot of our competitors will braze aluminum joints. That’s where they get the problems. It’s a tricky business,” he notes.
Besides the fact that leaks are difficult to repair on all-aluminum coils, Forty says that they’re almost impossible to clean. That’s because the coil itself is more fragile than a copper tube coil, so manufacturers place a heavy-duty cabinet around it for protection.
“With the heavy cabinet these units are hard to clean and maintain, so nobody does it,” says Forty. “If they do, they do a cursory clean-up job. You have to charge a decent price, because you have to take the case apart to get at it; then you have to use some special chemicals on those units, not the high-pressure hose, just regular water to clean it off. That doesn’t happen,” he notes.
Roger Tessier, sales manager, LRC Coil, sums it up when he notes that most contractors think copper tube/aluminum fin coils are of higher quality. “They are perceived as being a better piece of equipment and longer lasting in the field. Aluminum tubes are just nightmares to work on, so why ask for trouble?”
Publication date: 02/18/2002