When replacing a transformer, how should the new transformer be sized in relation to the existing load?

The correct sizing of a new transformer when replacing an existing one involves considering not just the current load, but also potential future increases in demand. Sizing the new transformer at 125% of the existing load provides a safety margin that accommodates unexpected increases in load, as well as any additional equipment that may be added over time. This ensures that the transformer operates efficiently under varying conditions and reduces the risk of overload.

Transformers need to handle transient conditions and short-term load increases, which could otherwise lead to overheating or failures. By targeting 125%, the new transformer will have the capacity to manage such fluctuations without significant risk to its longevity or performance. This practice aligns with industry standards that recommend considering future load growth when selecting transformer capacity.

Size recommendations like 100% of the existing load don't allow for growth, while options like 150% and 75% could result in overcapacity or insufficient capacity, respectively, which can lead to inefficiencies or inadequacies in meeting demand.