First, let me explain what ‘N’ is?
Explanation: In the accounting process of APC UPS design equipment, the letter “N” is generally used to refer to UPS design equipment. For example, the parallel redundant system is also known as N+1 design, while the dual system design can be represented by 2N. ‘N’ can be simply defined as the ‘need’ for critical loads. In other words, the power capacity that satisfies the power supply of the equipment being maintained. I device can be used to explain the purpose of ‘N’. For example, if the storage capacity requires 4 disks and the IT equipment contains exactly 4 disks, it is called an “N” design. On the contrary, if device I has 5 disks and only requires 4 disks for storage capacity, it is designed as “N+1”.
All along, when planning critical load power sources, it is necessary to fully consider future development so that the UPS system can provide 10 or 15 years of support for the load. It has been proven that planning according to this criterion is very difficult. In the 1990s, the concept of “watts per unit area” was proposed to facilitate the provision of a review framework and the comparison of various facilities. However, due to the lack of consensus on the meaning of “unit area”, this power measurement target has caused many misunderstandings. Recently, with the trend of skill simplification, people have gradually adopted the concept of “watts/rack” to represent system capacity. It has been proven that this measurement method has higher accuracy due to the simple calculation of the number of racks per unit space. Regardless of the choice of load “N”, it is important to select the equipment plan from the beginning to ensure that the design process proceeds in the correct direction. In short, the N system refers to a system composed of a single UPS module or a group of parallel UPS modules with a capacity equal to the critical load planning capacity. So far, this type of system is the most widely used equipment in the UPS profession. The small UPS under the desk belongs to N equipment. Similarly, for a calculation room with a planned design capacity of 400kW and an area of 500 square meters (5000 square feet), if a single 400KW UPS is selected or two parallel 200KW UPS are selected on the public bus, it is also classified as N equipment. Therefore, N equipment can be considered as the minimum requirement for supplying power to critical loads.