Finally, more reduced refrigerant dehumidifiers and environmentally friendly options are entering the market.
Indoor pool mechanical dehumidifiers have been large refrigerant users since the late ’70s, but a recent design development has reduced their refrigerant use by as much as 90%.
Mechanical dehumidifiers were an instant hit when they were introduced more than three decades ago. They were a new product that effectively controlled the space conditions and used considerably less energy than other approaches used to condition indoor pool spaces at the time. A significant green innovation was the use of the compressor waste heat to provide essentially free pool water heating. This energy recovery was also used for reheating the air up to space temperature set point after cooling it to condense moisture out of the return air stream. This helped to reduce operating costs and delivered more stable space and water conditions.
Change in the Industry
Although it wasn’t an initial concern then, these dehumidifiers also used dozens, even hundreds, of pounds of refrigerant for a moderately sized indoor pool. Refrigerant use didn’t become a concern until the Montreal Protocol international treaty was formed in 1987, bringing attention to the refrigerants that deplete the ozone layer. Ozone-depleting chlorofluorocarbon (CFC) refrigerants such as R-12 and R-11 have already been phased out. Their alternative—hydrochlorofluorocarbon (HCFC) refrigerant R-22—posed less environmental risk at the time but began to be phased down in 2010; it’s scheduled for complete phase-out in 2020.
Most dehumidifiers built prior to 2010 probably operate with R-22, which threatens indoor pool facility owners with looming financial liabilities if the unit loses most or all refrigerant due to a leak. R-22 prices have already skyrocketed since the EPA mandated its phase-out, and supplies have subsequently diminished. Therefore, total loss of hundreds of refrigerant for a moderately sized dehumidifier could result in a repair bill of more than $20,000 in service labor and refrigerant replacement costs.
Since 2010, dehumidifier manufacturers have used the HFC refrigerants R-410A and R-407C instead, but these refrigerants aren’t perfect either and have objectionable GWP (Global Warming Potential). They too are being examined for phase down. Owners of systems with larger refrigerant charges must face the facts that they may always be saddled with future refrigerant liabilities.
The best solution so far has been the pool dehumidifier industry’s recent move toward refrigerant reduction designs. A refrigerant charge can now be reduced as much as 90% compared to conventional dehumidifiers. This represents hundreds of pounds of refrigerant per dehumidifier that’s no longer needed.
New technology substitutes propylene glycol for refrigerant in parts of the system. Typically, conventional split system dehumidifiers transport refrigerant through copper piping to a remote air-cooled condenser for heat rejection. Conversely, reduced refrigerant systems reject heat into a glycol fluid loop, which is then transported outdoors through PVC or CPVC piping to an air-cooled heat exchanger called a dry-cooler, or fluid cooler. Glycol is environmentally friendly and 95% less expensive than today’s refrigerants. Furthermore, a glycol piping leak is less damaging than leaking refrigerant into the atmosphere.
Recent innovations by manufacturers have made these systems competitively priced with conventional systems regarding coolant and installation costs. These systems can perform at 5 to 7% higher efficiencies than conventional systems on normal days and equal efficiencies on the hottest summer days.
There are some significant side benefits to these systems, too:
• The unit’s refrigeration circuit used for dehumidification is factory sealed and poses less chance of job site errors that could lead to leaks. Thus, there’s no expensive site refrigeration work required by EPA-certified technicians when installing these systems.
• All challenges historically associated with large system refrigerant charges and field charging are totally eliminated.
• No copper pipes and soldering are needed to connect the dehumidifier to the dry cooler because less expensive PVC or CPVC piping is used. Therefore, there are no copper pipes subject to leaks or theft.
• Reducing refrigerant charges onsite can also add to LEED credits in new construction projects.
Protecting the Environment
Aside from environmental risks, refrigerants also subject building owners with additional considerations regarding compliance to ANSI/ASHRAE Standard 34-1010 (Designation and Safety Classification of Refrigerants) and ASHRAE Standard 15-2010 (Safety Standard for Refrigeration Systems) regarding safe refrigerant concentration limits in occupied spaces.
Split system refrigeration unit manufacturers can take a lesson from dehumidifier manufacturers that produce designs that substitute a majority of a unit’s refrigerant with glycol. Reducing refrigerant cuts costs in materials, installation labor, and maintenance, and it helps protect the environment.
Ralph Kittler is vice president of sales at Dehumidified Air Solutions (DAS). He is an ASHRAE Distinguished Lecturer and the reviser responsible for Chapter 25 (“Mechanical Dehumidifiers and Related Equipment”) for ASHRAE’s 2012 Systems and Equipment Handbook.