GENERATION Back it all W hen Renzo Rosso said “Diesel pioneered the idea of luxury denim, and we still drive this market. But it encompasses more: the consumers love the brand, the lifestyle, the mentality of Diesel”, it certainly had nothing in common with an equally sturdy, vintage, very widely distributed engine technology that was designed to operate originally from a vegetable oil. By this is meant the good old Diesel Engine (not the pants). This remarkable workhorse has been the backbone of the long haul and freight transportation network, as well as supporting the back-up generation system for decades. This longevity will amaze those who believe the late 1800s are prehistoric times, especially if viewed against the waves of disruptive technology of the latter part of the post WWII era. Diesel and gas generators for back-up power are nowadays easily accessible and come in an extensive variety of designs based upon the application and method of operation. Using diesel as fuel for standby generators costs less than equivalent gas generator models because of cheaper parts and components, including the starting framework, which does not need a spark ignition. 50 Diesel systems are viewed as more rough and dependable in extremely tough operating conditions and used to be prided on having longer working lives. Those who contemplate the sizing of a generator for business premises normally have to consider the following: the phase (either single or three); the power requirements; and the voltage requirements. Most business applications require a more prominent surge capacity, particularly when many motor loads are included or various sections perform work independently of each other and turn on and off as often as possible. Large motor inrush current control, typically above 150% of full load, is momentarily a daunting task and the generator has to be fit for purpose to handle this. The generator reserve capacity should be selected so that it can compensate for voltage drops across certain loads in such a way that a 30% voltage drop margin is maintained throughout. So now that we have established that size matters, what next? We all strive to be right, but hunches are by no means a replacement for good old empirical science. To do this, take out the meters and do some measurements. Here is a little procedure: Full load current measurements during peak usage = I total • Use a clamp on meter at the main distribution box, attach 3 phase clamps to all relevant phases and add the currents. V supply x (I total /3) x 1,000 (kW) for 3 phase • If the above was single phase then the current component is (I total /2) Use the calculations to estimate the capacity of the genset by measuring total current used by the plant, which, as explained earlier, is all about being in the ballpark for inrush estimation as well. Clamps on the meters are preferred in all the above, if you value life and limb! From here on a bit of reading is required, and for the sake of brevity the reproduction of the NEC, or equivalent emergency safety allocations for articles 700, 701, 702 and 708, are not reproduced here. If you already know the legally required emergency system requirements for ESI AFRICA ISSUE 1 2017