McQuay RPR User Manual

System Solutions From McQuay
McQuay Evaporative Condenser Rooftop System
How can I benefit from the substantial energy savings of evaporative condensing in a cost-effective, factory-packaged rooftop system?
McQuay RoofPak™ applied rooftop systems can be specified with an evaporative condenser, allowing you to benefit from substantial energy savings at the reduced design and installation costs of a factory-packaged system. Evaporative condensers can save as much as 40% on energy versus air­cooled alternatives, and they often draw less energy than any alternative HVAC system.
Features
• Seven sizes from 75 to 150 tons.
• Blow through (Model RPE) or draw through (Model RDE) cooling.
• Modular flexibility with multiple filter, fan, coil, heating and specialty equipment options to match strict application requirements.
• Factory assembled and tested units minimize field labor for installation and commissioning.
• Walk-in service vestibule with raised floor grate and drain pan contains water connections and most electrical, water treatment and refrigerant service components.
Benefits
Reduced Energy Consumption
• Up to 40% savings in condensing unit energy consumption versus air-cooled alternatives.
• Reduced peak electrical demand at design conditions allows unit electrical service to be downsized for lower installation costs and electrical demand charges.
• Airfoil fan selections require up to 20% less energy than competitive forward curve fans.
• Patented UltraSeal™ low leak dampers minimize losses (0.5% at 1.5” external static pressure).
• Factory-installed variable frequency drives further reduce energy consumption.
Designed For Long Life and Easy Maintenance
• Stainless steel spray enclosure and sump, copper tube bundles and polypropylene spray tree provide superior corrosion resistance.
• All refrigerant service can be performed inside the walk-in service vestibule – away from compressor noise and outdoor conditions.
• Sufficient space is available inside the service vestibule to house water treatment equipment required to prevent scale build-up and microbial growth.
• Easy removal and replacement of spray nozzles, condenser tube bundles and sump reduce service costs and down time.
McQuay RoofPak™ Evaporative Condenser Rooftop System
Model RPE (shown) – 75 to 150 tons (blow through cooling) Model RDE – 75 to 150 tons (draw through cooling)
Evaporative Condensing Reduces Energy Consumption
Air-cooled condensers reject heat to the ambient dry bulb (typically 95°F design) as air passes over the condenser surface. Evaporative condensers use a water spray that coats the condenser tubes (Figure 1). As air passes over the tubes, the spray evaporates and cools the tubes down toward the ambient wet bulb (typically 75°F). The lower condensing temperature reduces compressor work and energy consumption, resulting in lower electrical demand and consumption. In addition, the electrical service to the unit can be sized for lower amps to reduce installed costs.
Air-Cooled Condenser Evaporative-Cooled Condenser
Figure 1 – Evaporative condensers use the cooling effects of evaporation to reduce compressor work and electrical demand and consumption.
Typical Savings Versus Air-Cooled Rooftop Systems*
To illustrate the savings generated by evaporative condensing, consider a two-story shopping mall using several 125-ton VAV rooftop units and occupied 365 days a year. Tables 1 to 3 show the McQuay RPE condensing unit savings if the mall is located in Los Angeles, New York and Las Vegas.
Table 1 – McQuay RPE versus a typical air-cooled rooftop unit for a Los Angeles area mall.
Conditions Air-Cooled
Design Ambient Dry Bulb/Wet Bulb 95°F/72°F 95°F/72°F Electrical Consumption Rate (per kW Hour) $0.15 $0.15 Electrical Demand Rate (per kW) $24 $24
Efficiency (kW/ton) 1.15 0.85
Condensing Unit
Electrical Cost $30,200 $22,100
Percent Savings 27%
McQuay
RPE
Table 3 – McQuay RPE versus a typical air-cooled rooftop for a Las Vegas area mall.
Conditions Air-Cooled
Design Ambient Dry Bulb/Wet Bulb 110°F/72°F 110°F/72°F Electrical Consumption Rate (per kW Hour) $0.07 $0.07 Electrical Demand Rate (per kW) $8 $8
Efficiency (kW/ton) 1.40 0.85
Condensing Unit
Electrical Cost $19,042 $11,351
Percent Savings 40%
McQuay
RPE
Tables 1 to 3 show evaporative condensing savings of $5,500 to $8,100 (or 27% to 40%) of your annual condensing unit energy costs versus air-cooled systems.* The superior design of McQuay RoofPak applied rooftop air handling section can significantly increase these savings with features that include:
• More efficient airfoil fan selections versus commonly- used forward curved fans.
• Blow through cooling coil selection and Optimal Air Temperature systems reduce design cfm and fan energy costs.
McQuay RPE Energy Costs Are Competitive With Any HVAC System – Even Water-Cooled Chillers
Using the 0.85 kW/ton condensing unit efficiency, Figure 2 shows a comparison of a McQuay RPE evaporative condenser rooftop system with a 0.55 kW/ton water-cooled chiller system.* In this case, we assumed that the chiller system would have constant flow pumps and that it unloads to 0.46 kW/ton.
The energy performance of the two systems is very comparable (Figure 2). The RPE offers a significant part load advantage and the chiller offers a small full load advantage. Given that most air-conditioning systems operate at 60% load or less over the great majority of a typical year, the McQuay RPE may be the best equipment choice for energy savings and installed costs.
Chiller Offers Minor Full Load Advantage
Table 2 – McQuay RPE versus a typical air-cooled rooftop for a New York area mall.
Conditions Air-Cooled
Design Ambient Dry Bulb/Wet Bulb 95°F/75°F 95°F/75°F Electrical Consumption Rate (per kW Hour) $0.11 $0.11 Electrical Demand Rate (per kW) $18 $18
Efficiency (kW/ton) 1.15 0.88
Condensing Unit
Electrical Cost $17,860 $12,375
Percent Savings 31%
McQuay
RPE
RPE Offers Significant Part-Load Advantage
Figure 2 – McQuay RPE unit versus a 0.55 kW/ton water­cooled chiller system.
Designed For Long Life And Easy Maintenance
Corrosion Resistant
Stainless Steel Fan Decks With Severe Duty Motors and Corrosion-Resistant Fans
Stainless Steel Sump Copper Tube
PVC Spray Tubes
Bundles
Easy Maintenance and Service
Replaceable Nozzles
With 150
o
Spray Arc
Replaceable, Slide Out Tube Bundles
Polymer Tube Sheets
Stainless Steel Spray Enclosure
Walk-In Service Compartment
Perform Most Refrigerant Service In Comfort, Away From Compressor Noise
Access To Most Electrical Components
Marine Lights
Exhaust Fan
Access Doors On Both Sides
Replaceable Sump
Walk-In Service Compartment
Easy Compressor Access
Charging, Suction, Discharge and Liquid Schrader Connections
Solenoid, Sight Glass and Filter Drier
Raised Floor Grate and Drain Pan
Hot Gas Bypass Valves
Space For Water Treatment Equipment
* All energy analysis and comparison charts provided in this document are estimates and have been generated using McQuay Energy Analyzer™ software. Actual customer results may vary. For access to Energy Analyzer software, contact your local McQuay Representative. To locate your local McQuay Representative, visit www.mcquay.com or call (800) 432-1342.
McQuay RoofPak™ Applied Rooftop Systems
Total Indoor Environment Control, Only From McQuay
The evaporative condenser system is among the many innovative solutions for rooftop systems from McQuay that help you deliver a superior indoor environment at lower installed, operating and maintenance costs. Other innovations include:
• MicroTech II™ controls with our Protocol Selectability™ feature for easy, low cost integration with the building automation system of your choice.
• Patented DesignFlow™ precision outdoor air control system for precise measurement and control of outdoor air in support of ASHRAE Standard 62.1-1999.
• Patented SuperMod™ 20:1 turndown gas burner for precise temperature control in conventional or high minimum outdoor air applications.
• Fully integrated energy recovery wheel that recovers both heat and moisture from exhaust air for maximum energy and humidification savings, and to comply with ASHRAE Standard 90.1 efficiency guidelines.
• A liquid refrigerant subcooling reheat system for improved dehumidification control.
• Available with alternative non-HCFC refrigerant.
Contact your local McQuay sales representative for more information on how your building environment can benefit from innovative McQuay rooftop systems, or visit www.mcquay.com.
Air-Cooled Packaged Rooftop Systems
Model RPS (shown) – 15 to 135 tons (blow through cooling) Model RDT – 45 to 135 tons (draw through cooling)
Packaged Air Handlers
Model RAH – 12,000 to 50,000 CFM Model RDS – 5,000 to 20,000 CFM
Packaged Energy Recovery Systems
Model RPR (shown) – 15 to 60 ton packaged rooftop systems Model RAR – 5,000 to 15,000 CFM rooftop air handler
McQuay International delivers engineered, flexible solutions for commercial, industrial and institutional HVAC requirements with reliable
products, knowledgeable applications expertise and responsive support. McQuay products and services are provided through a worldwide network
of dedicated sales and service offices. In addition to Applied Rooftop Systems and air handlers, McQuay is your source for value-added HVAC
systems including Centrifugal, Screw and Scroll Compressor Water Chillers (10-2,500 tons), Evaporative Cooled Chillers (60-240 tons), Packaged
Chiller Plants, Skyline™ Outdoor Air Handlers (900-25,000 cfm), Destiny™ Indoor Air Handlers (600-15,000 cfm), Vision™ Customized Indoor Air
Handlers (900-50,000 cfm), Vertical Self-Contained Floor-By-Floor Units (15-125 tons), Coils, Fan Coils, Unit Ventilators, Water Source Heat Pumps,
Packaged Terminal Air Conditioners and Ductless Split Systems. For more information or the name of your local McQuay representative, call
1-800-432-1342 or visit www.mcquay.com.
©2004 McQuay International (800) 432-1342 www.mcquay.com ASP 31-791 (6/04)
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