The "HE-KU37CQS." The human presence sensor is located in the upper left part of the remote control for the bathroom.
The "HE-KU37CQS." The human presence sensor is located in the upper left part of the remote control for the bathroom.
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Panasonic Electric Works Co Ltd announced 16 models of heat pump water heaters (Eco Cute) including the "HE-KU37CQS," which saves energy used for keeping bathwater temperature constant by utilizing a human presence sensor.

By stopping keeping the bathwater temperature constant when no one is in the bathroom, it can reduce power consumption by up to 35% in winter, according to the company. The 16 models will be released July 10, 2009, in Japan. The "HE-KU37CQS," whose tank capacity and hot water supply pressure are 370L and 280kPa, respectively, will be priced at ¥819,000 (approx US$8,211).

The remote control will be sold separately. Panasonic plans to produce a total of 10,000 units of the 16 models per month.

The human detection function, which was introduced for the first time, consists of a "bathwater temperature learning function" and the human presence sensor. The former is a function to control the timing of heating bathwater based on the amount of decrease in bathwater temperature per hour calculated from heat retention properties that differ depending on bathtub type and season.

Panasonic's existing products measure bathwater temperature and reheat the water every 15 minutes regardless of the rate of heat decrease. In addition, water in the pipe flows into the bathtub every time bathwater temperature is measured, making it necessary to reheat the bathwater. With the learning function, the interval between heatings can be longer than 15 minutes, resulting in lower power consumption.

On the other hand, the company employed the human presence sensor not to affect comfort. Specifically, it is an infrared sensor equipped in a remote control installed on the wall of a bathroom. The sensor has a detection range of 120°.

When it detects a person coming into the bathroom, the HE-KU37CQS starts reheating the bathwater. And the water temperature becomes comfortable in about two minutes. The temperature is not high enough at the time the person steps into the bath, but s/he does not feel uncomfortable because his/her body is not warm enough either.

While the person is sitting in the bath, his/her body temperature and the water temperature are rising at the same time; therefore, s/he does not feel the bathwater is lukewarm.

As for other features of the HE-KU37CQS, Panasonic achieved an APF (annual performance factor of hot water supply) of 3.5 through enhancing the efficiencies of its heat pump unit and hot water storage unit. The APF of the existing product, "HE-KU37BQS released in 2008," is 3.3.

The company employed a back-pressure control mechanism with a small sliding loss for the compressor so that the heat pump has a higher efficiency in winter. In addition, by applying vacuum insulation material intensively to high-temperature portions in the storage unit, the radiation loss was reduced and the heat retention efficiency was improved by 10% compared with the existing product.