Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
Although physically speaking an instantaneous water heater transfers energy from the boiler to the service water through a heat exchanger, a delve into the EnergyPlus Input/Output Reference guide shows using a WaterHeater:Mixed instead of the heat exchanger shown in the plant loop image in this question. The guide suggests setting the volume of the mixed water heater to 1 gal (0.003785 m3) and set the Heater Control Type to Modulate to model an instantaneous water heater. Heater Fuel Type can be chosen, such as Electricity or NaturalGas. The WaterHeater:Mixed can also be placed in a Boiler Plant Loop, replacing the heat exchanger shown in the image in this question.
When using the WaterHeater:Mixed object, I discovered that the Water Systems energy consumption is identified in the OpenStudio Results Report in the Annual Overview End Use table, as well as the accompanying Pie Chart.
