Modified switchgear doesn’t stay listed on its own.
Tapping into existing UL-listed switchgear for solar, battery storage, EV charging, or a building addition alters the original listing. Before the utility will re-energize the gear, three separate parties typically have to sign off — the local building department, the utility, and a Field Evaluation Body. We are that third party.
Why This Comes Up
Bus taps have become routine. The compliance exposure hasn’t gone away.
Solar interconnections, battery backup systems, and property additions all tend to route through the same piece of equipment: the existing switchgear. Almost all switchgear installed in the U.S. is UL Listed, and altering it in the field is treated as a modification of that listed product — which can invalidate the original listing entirely.
The listing doesn’t travel with the intent
A tap made with good workmanship can still fall outside the original UL 891 evaluation the moment it changes clearances, bonding, or bus configuration.
Multiple authorities, multiple checklists
The building department, the utility, and the field evaluation body each look at the same modification through a different lens — and each has to approve it.
Shutdowns are expensive to get wrong
Utility de-energizations are scheduled events. Missing a requirement discovered on the day of the shutdown means rescheduling — and paying for it twice.
What Gets Checked
Three requirement sets. One evaluation.
Every modified-switchgear project we see gets measured against the same three frameworks. Understanding all three up front is what keeps a project moving instead of stalling at the shutdown.
Equipment Standard
UL 891 Compliance
Our core evaluation as a Field Evaluation Body
- Required air-gap clearances maintained from new taps to enclosure and adjacent bus
- Neutral disconnect link positioned on the load side of grounding connections
- Grounded source neutrals (solar, storage) tapped on the correct side of that link
- Tap hardware torqued to the switchgear manufacturer’s specification
- New tap sections properly bonded, barriered, and labeled
Electrical Code
NEC Requirements
How the installation is permitted to be wired
- Load-side taps and back-feed breakers held to the 120% busbar loading rule (705.12(B))
- Line-side parallel-power connections built to the gear’s design or routed through FEB review
- Service conductor raceway separation maintained when new sources tap the line side
- Neutral tap points located to preserve isolation for ground-fault testing
Utility
Utility Coordination
The party that ultimately re-energizes the gear
- Early notification before any physical modification begins
- Submittal package: room and section photos, nameplate data, marked-up modification location, single-line diagram
- Utility-jurisdiction sections (CT compartment, pull section) may require separate covers or barriers
- De-energized shutdown scheduled only once documentation is approved
How We Work
From single-line drawing to re-energized gear
Most surprises on switchgear modification projects happen because a requirement surfaces after the shutdown is already scheduled. Our process is built to surface it beforehand.
- Pre-tap documentation review
Send us the single-line diagram, nameplate data, and photos of the electrical room and the proposed tap location before construction starts. We flag UL 891 and NEC issues while they’re still easy to design around. - Utility & AHJ coordination
We help align your submittal package with what the utility and local building department expect, so the interconnection application and the field evaluation move on the same timeline. - On-site field evaluation
During the scheduled shutdown, we evaluate the completed modification against UL 891 and applicable NEC requirements — clearances, bonding, disconnect link placement, torque, and enclosure integrity. - Labeling & report
Compliant modifications receive a field evaluation label affixed to the equipment, backed by a written report the utility and AHJ can rely on for close-out. - Re-energization
Gear goes back into service with documentation in hand — no second shutdown, no open compliance questions.
FEB‑117
IAS-accredited Field Evaluation Body under ISO/IEC 17020:2012, covering power distribution equipment.
NFPA 790/791
Field evaluations performed to NFPA’s standard practice and recommended procedures for the field evaluation of electrical equipment.
SINCE 1994
Led by engineering staff with three decades in regulatory compliance across power distribution and industrial equipment.
EST. 1997
G&M Compliance, Inc. — Orange, California. Product safety testing, field evaluation, and certification.
Planning a tap, interconnection, or modification to existing switchgear?
Get us your single-line diagram and site photos before the shutdown is scheduled. We’ll tell you exactly what the field evaluation will look for.