The system pressure does not normally called ESP. There are a couple methods to calculation the system pressure drop. The calculation of the system pressure drop help you to select a proper pump to deliver the chilled water to your designated equipment.
You should draw your single line system diagram first. Once you know the length of the pipe, numbers of elbows, fittings(valves and etc.) and elevation change in your system, you can start to do the calculation. The most accurate method is to base on the velocity of the water in each section to calculate the dynamic loss. For the fittings, you can find the pressure loss from industrial cutsheets or ASHRAE handbooks. As you will aware now that this method can be time consuming.
The another method is to use the equivalent length. For example, an elbow is equivalent to 2'. Once you add up all the length, you base on the designed pressure drop per 100' to estimate the total system pressure drop and select your pump. This method is much less time cosuming but somewhat less accurate. In addition, the actual installation may not reflect your actual design due to the conflicts on site. Thus, you should add the safety factor in your calculation.
Both methods are documented in the ASHRAE Handbooks. Hope this help and good luck.
