自20世纪90年代初以来，日本和世界其他地方已经有了使用二氧化碳作为制冷剂的热泵热水器，并且已经安装了许多设备。然而，它们尚未在美国出现。一个主要原因是成本:热泵系统的成本将高于同等的电阻热水器，而二氧化碳系统往往具有更高的功能和成本。美国缺乏二氧化碳热水器的另一个原因是，现有型号与美国市场上常见的传统热水设备存在很大差异。在EcoCute标签下开发的型号通常有一个带室外热泵的室内水箱，并具有远程控制、洗澡水再循环回路等功能。 本研究考察了一家日本制造商开发并在欧洲销售的新型集成式二氧化碳热泵热水器，该热水器去除了二氧化碳系统的许多常见功能，适用于室内单位置安装。在实验室中，在各种条件下对集成的二氧化碳系统进行了测试，以确定性能。它在气候控制环境室内进行了各种环境空气条件的测试，也进行了近似的能量因数测试。被测试的系统有两种模式:舒适模式，压缩机功率高，系统总是充满电；以及一种经济模式，在这种模式下，压缩机功率较低，并且系统在预处理期间充满电- 设置（通常为夜间）小时，并在另一个预设时间段内仅部分重新加热。在两种模式下都进行了测试。该系统还被安装在田纳西州的一个测试家庭中，该测试家庭具有模拟职业和详细的数据监控功能。该系统安装在车库中，允许在不同的时间以各种操作模式运行。根据典型的负荷曲线，在家中控制取水。本文将概述测试和监控方法。将显示已完成的实验室测试和正在进行的现场测试的结果。引文:美国丹佛市ASHRAE会议论文

Heat pump water heaters using CO2as a refrigerant have been available in Japan and elsewhere in the world since the early 1990s, withmany devices already installed. However, they have yet to emerge in the United States. One major reason is cost: heat pump systems will costmore than an equivalent electric resistance water heater, and CO2systems tend to be have premium features and costs. Another reason for thelack of CO2water heaters in the US is that existing models have differed strongly from the conventional water heating equipment seen in the USmarketplace. Models developed under the EcoCute label often have an indoor tank with an outdoor heat pump, and features such as remotecontrols, bath water recirculation loops and others. This study examines a new, integrated CO2heat pump water heater developed by a Japanesemanufacturer and marketed in Europe, which removes many of the features common to CO2systems and is meant for indoor, single-locationinstallation. The integrated CO2system was tested in the laboratory at a variety of conditions to map performance. It was tested in climatecontrolledenvironmental chambers for a variety of ambient air conditions and also in an approximated Energy Factor test. The system tested hastwo modes: a comfort mode in which compressor power is high, and the system always charges to full capacity; and an economy mode in which thecompressor power is low, and the system charges to full capacity during pre-set (generally overnight) hours and reheats only partially during anotherpre-set time period. It was tested in both modes. The system was also installed in a test home in Tennessee which features simulated occupancyand detailed data monitoring. The system was installed in the garage and allowed to run in each of the operating modes at different times. Thewater draw was controlled in the home to a typical load profile. This paper will outline the testing and monitoring approach. Results for both thecompleted laboratory testing and ongoing field testing will be shown.