By Gary Mann
The reason that Water Heaters are not featured in Cymap by default is because they are not specifically featured in the BSEN806 Standard, but they can easily be added to your Cymap job. To calculate the expected flow to the Water Heater either calculate, using Edit>Appliance list,
e.g. 7 x WHB = 7 x 1 LUs = 7 LUs
or modelled as below. Use Display>Calculate to determine the HW Loading units required. (You could use the flow rate l/s and insert as Continuous, but that would not allow for diversity).
Once the HW demand (LUs) is known, Insert>Special, so that the Draw-Off value can be entered. Remember to input the “Highest Single Value” ( 3 ) as this decides which graph is used to convert the Loading Units to a flow rate in kg/s. if the flow rate is less than 300 LUs.
Finally, Tee this “Special” into the CW Supply simply by Inserting a CW Distribution Pipe, single clicking onto the Draw-Off arrow outlet, following the pipe route and then double clicking on CW pipe at the appropriate level to tee into this existing run.
This results in both the Cold Water and Hot Water demand summated together and a suitable flow rate through the water heater based on the probable use of each Wash Hand basin hot & cold Draw-Offs, (Taps).
Hope you find this helpful, let me know if you have any suggestions for future blogs.