Block ip Trap

Upgrading Your Project On Time and On Budget

14 Jul 2020

By Sam Daye

Adding alternative electrical energy production and storage systems can provide exceptional value to your facility. Often, this requires modification to your existing equipment and systems. However, any field modification made to listed equipment, including a switchboard line or load side bus tap interconnection, as covered in NFPA-70 article 230.82, means the modification to the switchboard may require an approval by the local utility company, or by the Authority Having Jurisdcition (AHJ). In most cases, the utility company or AHJ may request the installer to obtain field evaluation and labeling by an accredited Field Evaluation Body (FEB) prior to approval. 

Evaluating the interconnection requires ensuring that the switchboard still meets the requirements of both the subject electrical standards and applicable installation codes after the interconnection has been performed. Generally, investigation of the bus tap interconnections occurs during a utility shut down of electrical power to the facility; the evaluation must be completed before power is restored to the switchboard. Clear communication of the requirements for the installation, both prior to and during the shutdown, is critical for project success. 

Common procedures for field evaluation and labeling of switchboard bus taps 

The universal availability and use of electricity has come to define modern industrial life. Facilities looking to augment their use of energy with solar or fuel cell powered electricity and storage systems will realize exceptional value to their facility. The evaluation process will typically involve electrical drawings review, site inspection, and field testing. Pay particular attention to the following: 

  • Review of equipment drawings 
  • Suitability and compliance of installation 
  • Visual inspection of components 
  • Wiring methods and ratings 
  • Bus tap hardware ratings 
  • Proper hardware connection torque values
  • Electrical clearances 
  • Proper grounding 
  • Guarding of live parts 

The field evaluation for switchboard bus taps is generally completed in one site visit (during the utility shutdown, when the bus tap connections are installed). The typical steps taken during an evaluation include: 

  1. Drawings review: Electrical drawings are reviewed prior to shutdown to understand the scope of the project, and provide an initial review of the planned approach to tap the bus structure. 
  2. Utility Company and/or AHJ notification: Where required, a notification letter may be drafted and sent to the relevant utility company and/or the AHJ, informing them that a qualified FEB has been retained to perform the switchboard bus tap field evaluation.
  3. Installation plan review: On site, during shutdown, and prior to any switchboard modification, the overall installation plan is reviewed with the installer to evaluate compliance to the standards, and to assure that no changes will be made to the switchboard that would not comply. 
    1. During this review, any additional requirements pertaining to the installation that cannot be verified directly by drawings are reviewed with the installers to assure the installation will comply with all electrical standard requirements. 
    2. Typical requirements discussed usually include phase-to-phase and phase-to-ground creepage distances and proper spacings, bus ampacity, bus material type, electrical insulation, components and hardware ratings, wire sizing and insulation type, overcurrent protection, hardware torque values, and wire routing and bracing requirements. 
  4. Installation evaluation: As the installer proceeds to make the tap connections, the FEB will witness the proper torqueing of bolted connections to the bus structure, and complete their evaluation of the installation. 
  5. Electrical testing: Once the bus tap installation is complete, electrical testing will begin. This will generally include insulation resistance measurements of the bus tap interconnect. Additional tests could apply in unique situations. 
  6. FEB Label application: Following completion of the evaluation, and confirmation that the switchboard bus tap modifications comply with the applicable electrical standards and installation codes, the accredited FEB’s label will be applied to the compliant equipment before the switchboard is re-energized.
  7. Final documentation: A final evaluation report is issued to the end-user, the local utility company, and/or AHJ for their review and approval.  

The U.S. solar market is accelerating because of a growing understanding that renewable energy projects are sound investments. Augmenting existing energy in your facility can be cost efficient, but could also be costly if your electrical assets fail. Using accredited FEBs and partners that can support projects before and after installation. It helps to increase electrical reliability, and minimize the overall financial risk of the project.


Sam Daye is Supervising Engineer at eti Conformity. For more than 30 years, eti Conformity Services has been performing field evaluations and has completed more than 40,000 projects throughout the United States and around the globe.

eti Conformity Services |

Author: Sam Daye
Volume: 2020 July/August