Validating the Linear Equations for Different Wd Values:
When the linear equations are used for different values of Wd, such as the ASHREA Wd profile for one day, one should consider the total operation cycle of the EWH (ton and toff). Generally, the linear equations are valid when the total operation cycle (ton+toff) occurred within the specific time interval (hour of day). This means that the duration of ton and toff should fall within this time interval. For example, at the beginning of the day, if the EWH is turned on and turned off within the time period (00:00 am to 1:00 am), the linear equations in this period are valid.
Table 3-4 shows the values of ton, toff, and ttotal for the 24 h ASHREA Wd profile. This table gives the baseline of the value of Wd by which one can use these linear equations.