Your 20-year-old evaporative condenser is on its last legs. Maintenance has been called three times in the last week to address various problems, and the maintenance supervisor has noted extensive corrosion on many of the internal components. Still, with the economic environment heading into 2009 looking so uncertain, you’re not eager to invest the $20,000 or more that might be required to purchase and install a new unit. Can you buy yourself some time by overhauling your existing system? Or would you just be throwing money down the drain?
According to Gary Hudson, owner of G.R. Hudson Sales in Surrey, B.C., Canada, the answer to these questions depends on a number of factors related to the condition and location of the equipment, as well as the overall goals of the plant.
“Is the coil still in good shape? Is the equipment difficult to access? Does your plant need to increase cooling capacity or lower energy consumption? These are all questions to consider when evaluating whether to refurbish or replace an existing condenser,” Hudson says.
The Coil Is KeyHudson, whose firm provides consulting services to contractors and end users throughout western Canada as well as Washington and Oregon in the United States, is familiar with the challenges faced by engineers and plant owners. He has evaluated hundreds of evaporative condensers in his more than 40-year career, and most of the time he has been able to infuse new life into an aging unit. The key, he notes, is in the coil.
“The single most important factor in evaluating an existing evaporative condenser is the coil,” Hudson says. “If the coil is not corroded, you can probably refurbish the condenser and get several more years out of it at a substantially lower cost compared to installing a new one. However, if the coil is corroded, then you generally have to replace the unit.”
Hudson notes that most coils are supplied hot-dipped galvanized after fabrication. Users should be able to determine by sight inspection whether the galvanizing is corroded. If the results of the visual inspection are not clear, Hudson recommends hiring a metallurgist to X-ray the coil and verify that its condition is sound.
“You can repair the panels and all the other parts on a condenser, but if the coil has been attacked, then the condenser should be replaced. You’ll have leaks of refrigerant from the coil,” Hudson says.
In some cases, the location of the equipment can make condenser replacement difficult, if not impossible. According to Hudson, the coil itself can be replaced - either by disconnecting the piping, breaking the coil, lifting it off, and piping on a new coil; or by splitting the casing apart, taking the coil out of the casing, installing a new coil and replacing the casing. However, these options are expensive, and it generally is more cost-effective to replace the entire condenser coil casing section in cases where a coil failure has occurred.
Don't Overlook the Efficiency FactorIf an initial evaluation reveals that the condenser coil is in good shape, refurbishing the existing unit might be a viable option. But don’t overlook the efficiency factor. If the existing evaporative condenser is a centrifugal fan model that was built 20 or 30 years ago, it probably consumes a significant amount of energy.
“Compared to modern propeller fan condensers, centrifugal fan models nearly always will be double the horsepower due to the characteristics of the fan,” Hudson says. “With the high cost of energy today, it might be worthwhile to replace the old centrifugal fan unit with a lower-horsepower propeller fan unit and reap more efficient operation.”
You also should consider the designed condensing temperature of the system relative to the ambient wet bulb temperature. For example, in the Pacific Northwest and western Canada, where a 68°F (20°C) wet bulb design is standard, Hudson is a proponent of an 85°F (29°C) condensing temperature in order to provide maximum energy efficiency. “Thirty or forty years ago, units were designed for 95°F (35°C) condensing. The higher condensing temperature allowed for a smaller condenser, but it increased compressor horsepower, making the compressor work harder and consume more energy,” Hudson says.
Modern condensers are designed to optimize energy efficiency, so a plant that is seeking a significant reduction in energy costs might want to consider replacing its aging condenser with a newer model. However, Hudson notes that some inefficiencies can be addressed through a retrofit. “In many cases, an inefficient system can be refurbished to provide increased coil surface area and a lower condensing temperature, which will reduce the load on the compressor and subsequently reduce energy consumption,” he says.
Alternatively, plants with limited space that need increased capacity might want to consider resizing the coil to obtain greater cooling capacity at the same level of energy consumption. “As technology has advanced, the coils have become smaller,” Hudson explains. “As a result, a plant might be able to replace a six-row coil with a 10- or 12-row coil in the same box size to increase capacity by 10 to 20 percent at the same condensing temperature.”
Buying TimePlants that decide to pursue a repair and refurbishment of their existing equipment rather than a complete replacement ultimately are buying more than just parts and service - they’re buying time. According to Hudson, any repair and refurbish that adds another seven to 10 years to the life of your equipment is a good investment. But should you expect that kind of guarantee from a contractor?
“No one can guarantee how long a refurbish will last because so many different factors are involved,” Hudson says. “If you don’t have good water treatment and preventive maintenance programs in place, then it’s not going to last as long as expected.”
Hudson advises that plants work with experienced contractors that can provide a solid list of references. A one-year warranty on work is standard. Also, be sure to ask for - and implement - maintenance recommendations that can optimize the life of the equipment.
Regardless of the anticipated lifetime of the refurbished equipment, remember that this is only a temporary fix. Planning for a new condenser purchase now can help you budget appropriately and do sufficient research to identify the best replacement option.
G.R. Hudson Sales represents Baltimore AirCoil Co. in western Canada. For more information, contact Gary Hudson at (604) 538-2726 or email@example.com; or contact Steve Jaczun at Baltimore AirCoil, (410) 799-6200, firstname.lastname@example.org. BAC’s web site is at www.baltimoreaircoil.com.