Lawrence Berkeley National Laboratory

The objective of this study was to determine if it was feasible to collect information regarding energy use and hot water delivery from tankless gas water heaters using the sensors and controls built into the water heaters. This could then be used to determine the water heater efficiency ? the ratio of energy out (hot water delivered) to energy in (energy in the gas) in actual residential installations. The goal was to be as unobtrusive as possible, and to avoid invalidating warranties or exposing researchers to liability issues. If feasible this approach would reduce the costs of instrumentation. This paper describes the limited field and laboratory investigations to determine if using the sensors and controls built into tankless water heaters is feasible for field monitoring. It was more complicated to use the existing gas flow, water and temperature sensors than was anticipated. To get the signals from the existing sensors and controls is difficult and may involve making changes that would invalidate manufacturer warrantees. The procedures and methods for using signals from the existing gas valves, water flow meters and temperature sensors will vary by model. To be able to monitor different models and brands would require detailed information about each model and brand. Based on these findings, we believe that for field monitoring projects it would be easier, quicker and safer to connect external meters to measure the same parameters rather than using the sensors and controls built into tankless water heaters.