When should Part IV NOT be used for farm load calculations?

Part IV of the NEC specifically addresses load calculations for agricultural and farm-related facilities. In the context of agricultural installations, it provides guidelines tailored to the unique operational requirements and electrical loads of farms. When farm and dwelling loads are supplied by a common service, it complicates the load calculation because the total demand may not reflect the true usage of electrical service as intended for either type of load. Each has distinct characteristics and usage patterns, which could lead to inaccuracies in load assessment if included together.

Using Part IV strategies under these circumstances could result in an underestimation or overestimation of the electrical load, impacting the performance, efficiency, and safety of the electrical systems serving both the dwelling and the farm. Therefore, to ensure proper load management and compliance with electrical codes, it's crucial not to apply Part IV when both services are combined, as it undermines the precision that the guidelines aim to provide.

In contrast, for agricultural buildings, new installations, or seasonal farms, the specific load calculation methods provided by Part IV are designed to accommodate the particular requirements of these entities, ensuring accurate assessments based on their operational needs.