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Evaluation of the Freus Residential Evaporative Condenser System in PG&E Service Territory Maintenance requirements: Additional maintenance (relative to air-cooled systems) is essential to maintain the Freus performance advantage over time, and to ensure system components do not fail prematurely. Hard water, common to many Central Valley cities, contributes to excessive scale build up in systems that evaporate water. Basic maintenance, performed either by homeowners or HVAC technicians, is essential for product reliability. Long-term reliability: The Freus unit has been on the market since 2000, with most of the units sold over the past three or four years. With added maintenance requirements for the system, product reliability and service life are certainly real issues. Education in the Marketplace: Builders, homeowners, and HVAC contractors need to be educated on the benefits and issues related to evaporative condensers. Contractors in particular need to understand the design, sizing, and installation issues related to the technology. California Title 20 Appliance and Title 24 Building Standards Requirements “Evaporatively-Cooled” air conditioners (with cooling capacities less than 65,000 Btu/hour) are required by the California Title 20 Appliance Standards to achieve a minimum EER of 12.1 at the standard rating conditions of 95°F dry bulb and 75°F wet bulb. Currently the six Freus models shown in Table 1 are listed in the Title 20 database 4 . In October 2006 the Energy Commission approved a compliance option 5 for evaporative condensers. The compliance option includes algorithms for modeling of evaporative condenser performance. Evaporative condensers provide Title 24 cooling compliance credits of roughly 30-40%, with savings increasing in the hotter climate zones. Water Use Issues Table 1: Current Freus Title 20 Listings Model Capacity (Btu/hr) EER 10M0318 19,800 14.1 10M0327 26,000 14.5 10M0336 35,400 15.1 10M0342 41,500 15.1 10M0348 48,500 14.5 10M0360 59,000 14.5 In the past ten years evaporative condensers and other evaporative technologies have received increasing interest as concerns about energy efficiency and peak electrical demand has increased. At the same time, water agencies and environmental groups have started to express concerns 4 http://www.energy.ca.gov/appliances/appliance/excel_based_files/central_air/ 5 http://www.energy.ca.gov/2006publications/CEC-400-2006-003/CEC-400-2006-003-SF.PDF © Copyright, 2008, Pacific Gas and Electric Company. All rights reserved. Page 6
Evaluation of the Freus Residential Evaporative Condenser System in PG&E Service Territory about products that consume water, especially during peak periods when water demand is high. This tension between water vs. energy efficiency is an important issue in dry Southwestern climates where water resources are limited, but evaporative technologies also have the greatest energy savings potential. A compliance option approach proposed by Freus to the California Energy Commission under the Title 24 Residential Building Standards was delayed at least partially due to water use concerns expressed by the California Urban Water Conservation Council (CUWCC). These issues were finally resolved with the key evaporative condenser requirement being manufacturer certification that system water use does not exceed 9.0 gallons per ton-hour of cooling capacity. Water use is dependent on several factors, including the method used by the cooler to refresh water and prevent scale (mineral) build-up on evaporative media, outside air temperature and humidity, and system operating hours. The Freus application requires that an eligible system must use a pump down system to fully purge the sump on an eight hour run-time interval. Product Warranties The current Freus residential product warranty is 15 years on the fiberglass cabinet, ten years on the compressor and copper condenser coil, and five years on other parts. Labor is not included under the warranty terms. The warranty terms are consistent with conventional air-cooled equipment. Prior Research The Freus unit and its predecessors (the AC2 and AC2000) have been around for over ten years. Several recent studies are highlighted below: “Freus Water-Cooled Air Conditioners”, SMUD Customer Advanced Technologies Program Technology Evaluation Report. April 20, 2006. This report provides an overview of how the Freus system works in contrast to conventional aircooled air conditioners. The report also presents EER measurements completed on six Freus retrofit installations tested in 2003 (ranging from 7.7 to 11.8 at outdoor temperatures ranging from 91° to 101°F), all of which were determined to have insufficient supply air flow. Lower than expected EER’s were partially attributed to installation defects. The study also summarizes results of field inspections of 16 units. The units were inspected for mechanical issues and also evaluate the level of scale deposits on the copper heat exchanger. Homeowner satisfaction surveys indicated general satisfaction with their systems. The report can be found at: http://www.smud.org/education-safety/images-safety/cat_pdf/Freus%20(SMUD%20Report).pdf “Evaluation Project for Freus Evaporative Condenser Air Conditioners”, Prepared for SMUD by ADM Associates, March 2006. This report presents energy use simulation projections for the Freus system relative to three conventional system alternatives: a standard 13 SEER unit, a “typical” efficiency existing unit (7 EER assumed), and a premium efficiency 16 SEER unit. Simulations were completed on a 1,600 ft 2 house in Sacramento. Simulation results indicate annual cooling energy savings of 50.5% (764 kWh) and SMUD operating cost savings of $95 a year relative to the standard 13 © Copyright, 2008, Pacific Gas and Electric Company. All rights reserved. Page 7
Page 1 and 2: Pacific Gas and Electric Company Em
Page 3 and 4: Evaluation of the Freus Residential
Page 5 and 6: Executive Summary Residential evapo
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Page 17 and 18: Temperature (deg F) Evaluation of t
Page 29: Appendix A: Freus Product Brochure
Page 37 and 38: Start Date: August 01 00:00 Site: S
Page 39 and 40: RH Relative Humidity 100 90 80 70 6
Page 41 and 42: Sump Sump Water 90 18 85 16 14 80 1
Page 43: Equations 1 through 6 are a non-ite

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