What is a 30 Day Load Study and Why You Should Care?

Before you add more equipment to an existing electrical system, you should always do a 30 day load study. Why? Well, the National Electrical Code article 220.87 (see below) recommends all businesses do so to ensure you don’t cause a system overload, start a fire, and then burn down your building. A 30 day load study will give you the details about peak electricity demand to ensure your electrical panels have available capacity to add more equipment.

PMC-Rentals has a broad offering of test and measurement equipment available for rent. One of our most popular items is the DENT EliteProXC datalogger, primarily used for 30 day load studies. The Wireless Energy Datalogger is a complete solution for pinpointing electric usage and quantifying consumption by measuring, storing, and analyzing Volts, Amps, Watts, Volt-Amps (VA), Volt-Amps reactive (VAR), Kilowatts (kW), Kilowatt Hours (kWh), kVAh, kVARh, and Power Factor—up to 144 different parameters!  The perfect tool for 30 day load studies! In addition,  PMC-Rentals rents Power Quality Analyzers, Thermal Cameras, Ducters, Insulation Testers, and Fault Locators.

Per the National Electric Code, NFPA 70:

220.87 Determining Existing Loads. The calculation of a feeder or service load for existing installations shall be permitted to use actual maximum demand to determine the existing load under all of the following conditions:

  • The maximum demand data is available for a 1-year period.

Exception: If the maximum demand data for a 1-year period is not available, the calculated load shall be permitted to be based on the maximum demand (measure of average power demand over a 15-minute period) continuously recorded over a minimum 30-day period using a recording ammeter or power meter connected to the highest loaded phase of the feeder or service, based on the initial loading at the start of the recording. The recording shall reflect the maximum demand of the feeder or service by being taken when the building or space is occupied and shall include by measurement or calculation the larger of the heating or cooling equipment load, and other loads that may be periodic in nature due to seasonal or similar conditions.

(2) The maximum demand at 125 percent plus the new load does not exceed the ampacity of the feeder or rating of the service.

(3) The feeder has overcurrent protection in accordance with 240.4, and the service has overload protection in accordance with 230.90.

2016-12-14T14:31:51-06:00October 14th, 2016|