Consulting-Specifying Engineer - March 2009 - (Page 49) Regarding refrigerants: Chill out! Speaking of Jan. 1, 2010, that also is the date after which manufacturers may not produce new HVAC equipment containing HCFC-22 refrigerant (sometimes referred to as R-22). HCFC-22 is one of the hydrofluorocarbon (HCFC) refrigerants developed as a transitional replacement to chlorofluorocarbons (CFC), which damage the ozone layer of the earth’s atmosphere. The section of the U.S. Clean Air Act that addresses ozone depletion mandates that all HVAC equipment sold from Jan. 1, 2010, onward must contain an alternative to HCFC-22. Though the law does not specify alternatives, the most widely recognized onefor-one replacement for HCFC-22 is 410A. While 410A has no effect on ozone, it is a “greenhouse gas” and therefore contributes to global warming if vented to the atmosphere. However, when the Montreal Protocol mandated the phaseout of HCFC22 to address the ozone depletion potential, global warming potential was not on the table. Understandably, this change has generated some anxiety in the industry, which must implement another refrigerant phaseout. However, the aggregated opinion of the experts interviewed for this article was “chill out.” Smith Seckman Reid’s Banse said, “I’ve had conversations with owners who were concerned [about switching to 410A]. But the equipment manufacturers are telling me they’re still going to support HCFC-22 for 10 years. I think you should have a plan for replacing your equipment, but you don’t necessarily have to do it today.” Matt Muhlada, Trane’s North American product manager for large RTUs, agrees. “Some people are saying, ‘I’m just going to go ahead and buy a 410A system today.’ But they don’t need to do that. Now that refrigerant reclamation is mandated, HCFC-22 will be available for use in older systems,” he said. The Clean Air Act approves the use of recycled HCFC-22 in existing machines. In addition to requiring an alternative to HCFC-22 in new equipment, the Clean Air Act mandates a gradual phaseout of HCFC22. According to the Act, effective Jan. 1, 2015, no one may produce HCFC-22 (or any other “class II substance”) in an annual quantity greater than the amount that same person (which of course can mean a corporation) produced in “the baseline year.” Though the baseline year has not yet been announced, reliable sources suggest that it is likely to be retroactively set to 2007 or 2008 and that, over a several-year period, there will be a gradual reduction in the amount that can be produced compared to the baseline. An engineer’s wish list Pat Banse from Houston-based Smith Seckman Reid expressed that there are a few features that exist and are not being widely applied, or that would make RTUs perform a lot better if they were developed by manufacturers. Feature 1: A choice between exposed insulation and a solid liner on the inside of the RTU enclosure. “This is an indoor air quality issue,” said Banse, “because it’s hard to keep the units clean and a lot of dust and belt particles are conveyed into the space.” Many manufacturers have recognized this need and are offering options for double-wall construction in their larger packaged rooftop equipment and modular rooftop unit product lines. Hopefully, as owners and end users recognize the indoor environmental quality benefits associated with the ability to keep their equipment clean, market pressures will bring doublewall construction options to the smaller equipment sizes. Feature 2: Better quality seals on outdoor air dampers and return dampers. Banse said, “I’d like to see a damper that is actually leakage-rated like a true smoke control damper. Smoke dampers have edge seals and are leak-tested in a closed position for various static pressures and velocities.” This is another area where the necessary infrastructure is in place and simply needs to be embraced by the market. For example, Air Movement and Control Assn. International (AMCA) Publication 511-07 - Certified Ratings Program - Product Rating Manual for Air Control Devices includes damper leakage requirements very similar to the UL 555S requirements for smoke dampers. And at least one manufacturer uses a rated double-skin, ultra-low-leak airfoil design with blade and jamb seals as the standard offering in its modular RTU product line. It’s likely that others will follow suit and that the higher quality products will penetrate the smaller packaged equipment sizes as consumers become increasingly aware of the advantages (see sidebar, “Damper leakage limits free cooling” on page 50) driving demand up and prices down. Feature 3: Better acoustical data on the fans as applied in the RTU. According to Banse, “You have to be careful with the discharge component in particular to avoid fan noise going down your ductwork. You have to pay attention to the location of the fan and to the static pressure you’re designing to.” While manufacturers of AMCA-certified fans publish certified fan discharge sound levels for their fans under AMCA 311, these ratings do not take into account the impact of the installed configuration of the fan when it’s applied in a RTU. “When a fan is operating in an inefficient part of its curve, the lost power could result in increased noise and vibration,” said Joe Brooks, director of engineering for AMCA. “ASHRAE is sponsoring several research projects to not only increase their database of air system effects, but to include sound system effects. Anecdotally, it is logical that any adverse system design that would cause an aerodynamic system effect w also ould cause an acoustic system effect. One purpose of these ASHRAE Research Projects is to quantify the acoustic system effects.” Consulting-Specifying Engineer • MARCH 2009 49
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