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Connected Load Studies are used to identify overall circuit loading, as well as peak usage. The load study data can offer insights into possible better management of load utilization that can result in significant reductions in energy costs. In addition, the National Electrical Code (NEC) requires a connected load study to determine whether new loads and breakers can be added to a panel. To meet NEC requirements, the study must be conducted in accordance with NEC 220.87.

Bruce sez, “When doing a connected load study, you are really concerned about two things.  One is the loading and ampacity of the breaker and the other is the continuous load, i.e., the max load for any 180-minute period over the study period.  With circuit breakers you have to be concerned about the max load with respect to the breaker rating, but the NEC also says that you cannot (should not) exceed 80% of the CB rating with a continuous load.  So, when doing a connected load study, you really have to look at the load’s maximum average demand (MAD) with respect to the circuit breakers rating as well as the continuous load not exceeding the 80% of the CB rating.”

Metsys_current_logger-demo2.jpgThe NEC 220.87 study is based on collecting average current data over 15-minute intervals, continuously recorded over 30-days. The ideal instrument for this type of study is the METSyS Current Datalogger, available exclusively in North America from POWERetc. The unit is equipped with a rechargeable battery providing a minimum of 72 hours of operation to accommodate the 72-hour OSHPD monitoring requirements and a 120-260V power supply for longer duration recording periods.

With POWERetc’s proprietary Excel macro software, the exported 15-minute increment data is used to calculate the maximum average (or peak average demand and  the moving average of 180-minute data required to determine the maximum connected load. Conducting a NEC 220 Conducted Load Study accurately will go a long way to avoiding oversizing or over loading of panels and circuits. 

Below is a sample of the results for a 30-day period. The POWERetc software can be used to provide a complete report, including details of seasonal loads, planned additional or removal/replacement of existing loads and other variants, to satisfy the most discerning electrical inspector.

Hire POWERetc for your load study:

POWERetc offers a complete service for Power Quality monitoring, or Load Studies, or both. Our consulting service includes installation and set up of monitoring equipment, data analysis and report preparation. Client reports and monitoring data can be posted on a password protected web site for access by the client or e-mailed directly.

Or, buy or rent monitors from POWERetc for your load study and we'll train and support you:

POWERetc sells and rents a variety of monitoring equipment configured for the clients' needs and provides training and application support. We can also review the data with you as part of the overall rental package. For specific information visit the Rental Equipment section of the web site.

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The METSyS Energy Logger was designed specifically for this application. This self-powered data logger measures 3 or 4 phase current complying with NFPA’s National Electrical Code NEC 220 Article 220.87 and creates uniform load calculations in accordance with the requirements of the California Electrical Code (CEC).


POWERetc Corporation

Corporate Headquarters
3350 Scott Blvd,
Bldg 55-03
Santa Clara, CA 95054

Phone: (408) 540-3199
Email: info@poweretc.com


Bruce B. Lonie
Phone:  (408) 666-6500
Email: BruceL@poweretc.com