Hot Water in the Hereafter

Larry Acker demonstrates the Metlund system to water heating experts at a meeting in Sacramento.

The two-day seminar, organized by Jim Lutz of the Lawrence Berkeley National Laboratory and Gary Klein of the California Energy Commission, was focused primarily on developing solutions to the shortcomings of DHW systems. In addition, participants were shown a few innovative technologies while brainstorming ideas about the road ahead.

The Microtherm Instantaneous Water Heater, manufactured by Microtherm, Incorporated, also made an appearance. This device can heat cold water instantaneously and has no water tank. Unlike other instantaneous water heaters, the Microtherm device has a variable setpoint and optimizes the amount of electricity used to heat water to a given temperature. With high flow rates and very cold inlet water, the system can require up to 28 kW of electricity, and thus needs a fairly large electrical service for its operation.

Water circulation was also discussed at the session. Rick Burris, of Vanguard Industries, demonstrated his Manabloc distribution system, which has been on the market for ten years. Manabloc reduces the amount of water drawn from a hot-water tank, using small-diameter flexible plastic tubing and a manifold to separately feed every hot water tap in a house. The 3/8-inch lines hold much less water than a 3/4-inch main with 1/2-inch branches. Also, plastic piping draws less heat from the water than metal does, resulting in quicker hot-water delivery, while the flexible plastic makes for easy installation.

Carmine Vasile described his gray-water heat exchanger, which recaptures roughly half the heat that is usually lost from shower drain water (see Dampers, Reclaimers, and Pumps--Oh My!). Vasile emphasized that hot water systems can be configured in either closed or open loops. In the more common open-loop system, heated water leaves the drain as wasteful output. In a closed-loop hot-water system, heat, and potentially water, could be recirculated for reuse, thus reducing demand for both.

The Metlund system, another circulation device, was demonstrated by Larry Acker, president of Advanced Conservation Incorporated. The system saves time as well as water by delivering hot water 80% faster to the tap (see Dampers, Reclaimers, and Pumps--Oh My!).

So what about the future? Several obstacles currently stand in the way of building better water-heating systems. Among them are low consumer demand; lack of knowledge among builders, architects, and contractors; few financial incentives; inconsistencies in the code structure; and the lack of an accepted rating structure that evaluates the whole DHW system.

To begin the work of overcoming these hurdles, seminar participants discussed ways to evaluate the whole DHW system. They settled on a performance-based approach that relies on five key criteria. These were: measured performance at the fixture (for example, flow rate and waiting time); reliability; health and safety; environmental impact (including life cycle analysis and resource depletion); and system cost.

To simplify the existing regulatory structure, increase innovation and flexibility, and gain acceptance for a systems approach, it was suggested that residences receive a specified water-heating allowance. This allowance could be measured in watts per ft2 of living space, and, in effect, would set an efficiency floor.

This hot-water seminar was just the first in a series of meetings that will discuss the future of hot water. For more information or to find out about the next meeting, contact Gary Klein at the California Energy Commission. Tel: (916) 653-8555; E-mail: gklein@energy. state.ca.us.

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