Effect of Water Quality on Residential Water Heater Life Cycle Efficiency. Phase 1. Preliminary Investigation and Planning

摘要

The report presents the results of Phase I of a three-year field test to quantify the effect of scale build-up in residential water heaters and to determine the benefits and limitations of common water treatment methods. Phase I is a preliminary investigation of scale build-up in water heaters and heater performance. Phase II will involve a two-year field tests in several U.S. cities. Phase I results confirm the rapid rise in scaling rate as water temperature increases from 140 deg F to 180 deg F. The most effective method for monitoring scale buildup proved to be periodic visual inspection and physical removal of the scale for drying and weighing at the end of the tests. Ultrasonic monitoring of scale thickness did not prove feasible. Recovery efficiency measurements and service or operating efficiency measurements on the water heaters tested did not indicate any measurable degradation of heater efficiency due to scale build-up. Also, a small change in burner performance can have a significant effect on water heater efficiency. An experimental test facility that can operate up to 20 residential water heaters has been set up; it includes water treatment equipment for softening and polyphosphate treatment.