Field Evaluation When a Product Has No Listing
Why this matters
Every few months a shop meets equipment with no listing behind it: a control panel a previous contractor built on site, an appliance a homeowner imported, a listed unit somebody modified until the listing no longer describes it. The inspector will not approve it as it stands, and the customer does not want to hear "rip it out". Field evaluation is the legitimate middle path, a recognized body inspecting that one unit on site and labeling it if it passes. It is also slower, narrower and less certain than most people expect, and the shops that use it well are the ones that ask the official first and know which equipment is worth evaluating at all.
What field evaluation is
A field evaluation is an inspection and limited testing of one specific piece of installed or ready-to-install equipment, at its location, by a qualified third-party field evaluation body (FEB), against the safety standard that would apply to that kind of equipment. If the equipment passes, or passes after corrections, the FEB applies a field label to that unit and issues a report.
Two consensus documents frame the practice. NFPA 790 sets out the competency requirements for third-party field evaluation bodies. NFPA 791 is the recommended practice for how unlabeled electrical equipment is evaluated. Neither is law by itself: an authority having jurisdiction (AHJ) may adopt them or refer to them, may keep its own list of FEBs it accepts, or may simply judge each request on its merits. Some testing laboratories that certify products also run field evaluation services, and other organizations are field evaluation bodies only.
What the field label covers, and what it does not
One unit. The label covers the serial number in front of the evaluator, not the model. A second identical unit needs its own evaluation.
As found, or as corrected. The evaluator assesses construction against the applicable standard: enclosure, spacings, component ratings and certifications, protection, grounding and bonding, markings. Where the unit falls short, the report lists corrections, which someone has to make before the label goes on. The evaluator does not redesign the equipment.
At that moment. A later modification puts the unit outside the field label exactly as it would put a listed product outside its listing. See related: Why a Field Modification Can Void a Listing.
Not the installation. The field label covers the equipment. The wiring to it, its location, clearances and protection remain the installer's job under the adopted code, inspected in the ordinary way.
Not approval. A field label is evidence the AHJ may accept. Approval is still the official's decision. See related: Listed, Labeled and Approved: Three Words That Are Not the Same.
When an official is likely to accept it
Acceptance varies by jurisdiction and by official, so the practical rule is to ask before you hire anyone. In general:
- Electrical equipment is where field evaluation is most established, and most electrical inspectors know the process and will accept a field label from an FEB they consider qualified, often one meeting NFPA 790.
- Gas-fired appliances are a harder case. Fewer bodies offer field evaluation for them, and many officials will not accept anything short of a factory listing for a combustion appliance. Ask before spending anything.
- A jurisdiction with its own list of accepted FEBs, which some large cities and some state electrical programs maintain, accepts only bodies on that list.
- Workplaces have their own route. Under OSHA's electrical rules, 29 CFR 1910.399 allows, in its definition of acceptable equipment, custom-made equipment shown safe by the manufacturer on test data the employer keeps, and equipment of a kind no NRTL certifies when inspected or tested by a state or local authority responsible for enforcing the electrical code. That duty runs to the employer for its own workplace, and it does not change what a building official requires on a permit. See related: What a Nationally Recognized Testing Laboratory Is.
When you ask, ask three things in one call: will you accept a field label for this equipment, from which bodies, and do you want to see the evaluation report before or at inspection.
What it costs in time
Field evaluation is scheduled work, not a same-day fix. A typical sequence:
- Request and documentation. The FEB wants nameplate photos, drawings or a wiring diagram if one exists, a component list, any manuals, and the intended use. A few days to assemble, longer if the equipment came with nothing.
- Scheduling. Days to a few weeks, depending on the body and your region.
- Site visit. Usually hours for a single piece of equipment. The evaluator inspects construction and runs tests appropriate to the standard.
- Corrections. If the report lists any, someone makes them and the evaluator verifies, sometimes by photo, sometimes with a second visit.
- Label and report. Applied at the final verification, report issued after.
From first call to label, two to six weeks is a reasonable planning range for a straightforward electrical item, with the low end where documentation is ready and no corrections are needed. Price it to the customer as a multiple of a few hours of the evaluator's time plus travel, and compare it honestly with the cost of a listed replacement. For a small appliance, a listed replacement almost always wins. For custom or high-value equipment that cannot be replaced off the shelf, evaluation often wins.
Equipment that ends up needing it
Custom control panels built on site, even entirely from certified parts. The assembly is a product category of its own and a box of listed parts is not a listed assembly.
Imported equipment carrying a foreign conformity mark rather than a US listing. A European conformity mark is a manufacturer's declaration under EU law, not third-party certification to a US standard.
Modified listed equipment, where the modification cannot be undone and a listed replacement is impractical.
Equipment whose listing cannot be established: old units with missing labels whose maker no longer exists. See related: How to Find Out Whether Old Equipment Was Ever Listed.
Worked example: two items, one house, opposite answers
A shop takes over service at a house with a backyard spa and a home sauna, both installed years ago by a contractor no longer in business. A remodel permit has the inspector looking at both, and neither carries a US listing.
Item 1, the spa equipment control panel. A metal enclosure built on site: a contactor, a timer, a GFCI breaker, terminal blocks and a small transformer. Every part inside carries a lab mark, and the enclosure itself is a listed empty enclosure. No label covers the assembly. The shop calls the inspector, who confirms a field label from an FEB meeting NFPA 790 will be accepted and asks to see the report before the final. Documentation: the shop photographs the nameplates and draws the wiring as found, about 2 hours. The evaluator's visit takes about 3 hours and finds two corrections: a missing bonding jumper on the door, and the transformer secondary lacking the overcurrent protection its own rating calls for. The shop makes both in about 1 hour, the evaluator verifies by photo, and the label goes on. Elapsed: about 3 weeks from first call. Shop labor: about 3 hours (2 documenting plus 1 correcting). The alternative was a listed replacement panel plus rewiring the equipment pad, which the shop estimated at about 2 days, so evaluation was the better answer for this customer.
Hazards on that job: the panel was worked de-energized only, locked and tagged at its supply breaker and proved dead on a tester checked on a known live source before and after, per NFPA 70E Article 120 (120.5 in the 2021 edition, renumbered in 2024); and on re-energizing, the tech stood to the side of the panel, closed the supply, and pressed the GFCI test button to confirm it tripped and reset before the spa ran, because a spa is exactly where a dead GFCI kills someone.
Item 2, the sauna heater. An imported electric heater designed for a three-phase supply at a European voltage, wired by the old contractor to the house's single-phase 240 V supply through a field-built adapter of conductors and a relay. It carries a European conformity mark and no US listing. The shop calls the same inspector, who says plainly that a field label on this heater will not be accepted because the unit is being operated on a supply it was not designed for, which no evaluation can cure. Field evaluation assesses the equipment against a standard; it does not convert it. The shop quotes a listed heater rated for the house's supply, and because a field-built adapter feeding a heater off its design supply is a fire risk today rather than a paperwork problem, it asks the homeowner's permission to switch the heater's breaker off and tag it out of service until the replacement goes in, and writes down the answer. Elapsed time to the decision: one phone call.
Why the two went opposite ways. The panel was ordinary construction that could be measured against a standard and corrected in place. The heater's problem was its design basis, and the evaluator would have had to approve a supply arrangement the manufacturer never intended. Asking the official before hiring anyone saved the cost of an evaluation that would have failed.
How to verify the field label will hold
Before you close the job, confirm four things and put each on the job record: the inspector's acceptance of field evaluation for this equipment, in writing or noted with name and date (see related: How to Document a Code Interpretation You Were Given); the FEB's name and the report number; the serial number on the field label matching the unit; and every correction in the report marked as completed and verified. If any one is missing, the next inspector or the next insurer will treat the equipment as unlisted.
References
- NFPA 790, Standard for Competency of Third-Party Field Evaluation Bodies, and NFPA 791, Recommended Practice and Procedures for Unlabeled Electrical Equipment Evaluation, in the editions your AHJ references, where it references them
- 29 CFR 1910.399, definition of acceptable equipment for workplace electrical installations
- NFPA 70E Article 120 (120.5 in the 2021 edition, renumbered in 2024), for proving equipment de-energized before working on it
- See related: What a Listing Mark Means and What It Does Not; How to Request Approval for an Alternative Method