Noncurrent-Carrying Wiring Device Manufacturing (U.S.) — NAICS 335932

An investor's primer. Figures marked as reported come from federal statistics and company filings; statements about where things are headed are labeled as judgments, not facts.

1. Overview

Every electrical system needs two kinds of parts: the pieces that carry current (wires, switches, outlets) and the pieces that don't — the boxes, conduit, fittings, faceplates, cable trays, hangers, and insulators that route, protect, support, and enclose the live wiring. NAICS (North American Industry Classification System) code 335932 covers U.S. factories that make that second group: noncurrent-carrying wiring devices [1]. "Noncurrent-carrying" describes the product's primary function, not whether it can ever conduct electricity: metallic conduit, boxes, and fittings may form part of a grounding or fault-current path [1][2].

Why an investor cares: this is an unglamorous but essential "picks-and-shovels" layer of construction and electrification. Conduit and cable management go into every data center, factory, warehouse, hospital, solar farm, and apartment block. Demand tracks how much building and grid work is happening, and the economics are a commodity-conversion business — turn steel, plastic resin, and aluminum into coded, listed parts and sell the spread. That makes it cyclical and, at times, extraordinarily profitable.

Public-market investors can own it through a handful of listed electrical manufacturers, one of which (Atkore) is close to a pure play. Private investors encounter it as family-owned pipe-and-conduit makers, private-equity roll-ups, and regional fabricators — a long tail of smaller companies that rarely trade publicly. Both routes are covered in Sections 4 and 10.

2. What it is and how it's structured

Scope. NAICS 335932 establishments primarily make noncurrent-carrying wiring devices, including [1]:

• Electrical boxes — junction, outlet, switch, and floor boxes (metal and nonmetallic)
• Conduit and fittings — the raceway tubing that protects and routes wire (steel EMT/IMC/rigid, PVC, aluminum, HDPE, fiberglass) plus couplings, connectors, elbows, and straps
• Faceplates and wall/outlet covers
• Transmission pole and line hardware — the brackets and mounting gear on utility poles
• Electrical insulators — except porcelain/ceramic and glass types

Manufacturing processes. The industry spans several distinct methods. Steel conduit, tubing, boxes, and covers require tube forming, stamping, welding, galvanizing, or coating. Plastic conduit and fittings use PVC or other resin extrusion and molding. Utility-line products employ formed galvanized or aluminum wire, castings, fasteners, and engineered assemblies. Preformed Line Products, for example, identifies galvanized wire, stainless steel, aluminum-covered steel wire, aluminum rod, resins, rubber compounds, and aluminum castings as principal inputs [3].

What it explicitly excludes — and the adjacent codes to know:

• Current-carrying wiring devices (switches, receptacles, plugs, connectors that conduct) → NAICS 335931 [1]
• Porcelain and other ceramic insulators → NAICS 327110 [1]
• Glass insulators → NAICS 32721 [1]
• Wire and cable itself → NAICS 335921/335929; metal stamping and plastics extrusion done for other end-uses sit in 332xxx / 326xxx

Ownership mix. The industry is a barbell: a small number of large, scaled manufacturers — several publicly traded, several family- or private-equity-owned — sitting on top of a long tail of small niche fabricators (flexible conduit, fiberglass conduit, specialty fittings). Products reach the jobsite almost entirely through electrical distributors (Graybar, Rexel, WESCO, Sonepar), and are specified by engineers and contractors according to safety codes and third-party listings, which matters a great deal for competitive positioning (Section 7). Breadth of catalog, immediate availability, code listings, and the ability to consolidate many products onto one order matter alongside unit cost. Atkore describes its model as serving contractors through the electrical-wholesale channel, supported by regional service centers, short order cycles, and co-loaded deliveries [4].

3. How big it is

Federal statistics for NAICS 335932 (U.S.):

That works out to roughly $70,700 in average annual pay per worker (payroll ÷ employees, 2023) [6], and about 1.4 plants per firm — a sign that several companies run multiple factories.

Concentration (2022 Economic Census) [5]:

• Top 4 firms = 42.8% of receipts (CR4)
• Top 8 = 62.5%; Top 20 = 89.3%; Top 50 = 98.6%
• Herfindahl-Hirschman Index (HHI, a market-concentration score) = 648

Read together, these say the structure is top-heavy but not a monopoly: the four biggest firms make nearly half of domestic output, ~50 firms account for essentially everything, and the remaining ~60 are tiny. An HHI of 648 sits well below the 1,500 mark U.S. antitrust regulators treat as "moderately concentrated," so no single firm dominates.

Undercount caveat — this figure understates the real U.S. market. Two reasons. First, the Economic Census counts only plants primarily engaged in 335932; diversified electrical majors (Eaton, ABB, Legrand, Schneider) make boxes, conduit, and cable management inside plants classified under other codes, so their output is partly invisible here. Second, "value of shipments" measures what U.S. factories ship, not what the U.S. consumes — and imports of steel conduit (notably from Mexico) and fittings (from Asia) supply a meaningful and growing share of domestic use [8][9].

Analytical warning. The most common error is to quote the much larger "wiring devices" market as though it were this industry. NEMA itself warns that some industry tables consolidate 335931 and 335932 [10]. That combined category includes current-carrying switches, receptacles, and related devices and is not a valid market-size proxy for noncurrent-carrying products. A second error is summing public-company electrical-segment sales to estimate market size: those segments contain cable, controls, switchgear, cooling, current-carrying connectors, and international sales belonging to other classifications.

4. The investable universe

There is no clean, single-name "conduit ETF." Public exposure comes through electrical-equipment manufacturers where noncurrent-carrying wiring devices are the whole business (Atkore) or a large slice of it (the rest). Scale below is total company revenue unless noted; for the diversified names, 335932-type products are only a fraction.

Major private and other owners — where much of the industry actually sits:

• Zekelman Industries / Wheatland Tube — the largest independent steel pipe-and-tube maker in North America and a leading steel-conduit (EMT/IMC/rigid) producer; family-owned [9].
• Southwire — large family-owned wire and conduit manufacturer.
• Cantex — PVC conduit, private.
• Robroy Industries — private, family-controlled manufacturer of conduit, raceway, and enclosures [15].
• IPEX / Aliaxis — PVC electrical conduit and fittings; parent Aliaxis is privately owned [16].
• Champion Fiberglass, Electri-Flex, Anamet Electrical — specialty (fiberglass, flexible) conduit, private.

Bottom line: only Atkore gives near-pure exposure; everyone else is a diversified electrical or industrial company where this industry is one line among several. Preformed Line Products offers the narrowest public exposure to utility transmission and distribution hardware specifically.

5. How the money works

This is a manufacturing spread business, and the metrics that matter are the manufacturing ones — input costs, pricing, capacity utilization, and volume — not anything resembling utility rate base or real-estate yields.

• The core equation. Buy commodities (hot-rolled and galvanized steel, PVC resin, aluminum, HDPE, fiberglass), convert them on high-fixed-cost mills and extrusion lines, and sell finished conduit/boxes/fittings through distributors. Profit ≈ (selling price − input cost) × volume − conversion cost. Because a large share of cost is fixed plant, capacity utilization swings margins sharply. Materials represent approximately half of cost of goods sold at companies like Hubbell [13].

• Pricing is the swing factor — and it mean-reverts. The clearest illustration is Atkore's Electrical segment. Pandemic-era supply shortages let selling prices run far above replacement cost, pushing adjusted EBITDA margins above 30%. As supply and imports returned, prices normalized hard — fiscal 2025 average selling prices fell 15.1% while volume rose only 0.2%, dropping the segment's adjusted EBITDA margin to 16.5% from 30.9% a year earlier [4]. Atkore's full-year FY2025 net sales dropped ~11% to $2.85 billion with adjusted EBITDA more than cut in half. The lesson for investors: windfall pricing above replacement cost is temporary; underwrite the through-cycle margin, not the peak.

• Commodity vs. engineered. Plain conduit is close to a commodity — low differentiation, price competition, and heavy import exposure. Value migrates toward engineered systems: cable-management systems, enclosures, fiberglass and specialty conduit, and code-listed fittings, where brand, being "spec'd in" by engineers, and third-party listings create stickiness and better margins. Preformed Line Products illustrates engineered-product economics with a 31.2% gross margin on its utility-line hardware [3].

• Inventory and working capital. Because metal and resin sit in inventory, reported margins carry holding gains and losses as commodity prices move — a source of quarter-to-quarter noise. Inventory made with expensive material can be sold after market prices have declined, and windfall spreads can reverse quickly. Channel destocking and restocking by distributors amplifies the underlying construction cycle. Atkore does not generally hedge raw-material purchases, increasing exposure to spot and inventory effects [4].

• Seasonality. Sales are normally stronger in fiscal third and fourth quarters because weather is more favorable for construction; maintenance and remodeling become a larger, stabilizing share during weak construction periods [4].

6. What drives demand

Demand is derived from construction and electrification activity:

• Nonresidential and industrial construction — factories, warehouses, offices, institutional buildings — the biggest single driver, and interest-rate sensitive [17].
• Data centers — a standout tailwind. Hyperscale campuses are conduit- and cable-management-intensive; industry estimates put roughly a quarter of a large data center's electrical budget into cable containment, and manufacturing, warehouses, and data centers together drove the majority of recent commercial/industrial construction growth [18][17].
• Utility capital spending — already substantial. EIA reported that real U.S. electric-distribution capital expenditure reached $50.9 billion in 2023, up $6.5 billion from the prior year. Within that total, utilities spent $17.4 billion on overhead lines, poles, and towers and $11.8 billion on underground lines; transmission capital expenditure was another $27.7 billion [19]. These figures are not 335932 revenue, but they describe the investment pools against which line hardware, conduit, and enclosures are sold.
• Electricity demand growth — EIA reports U.S. electricity demand grew approximately 1.7% annually from 2020 through 2025, compared with 0.1% annually from 2005 through 2019, with data centers a major cause. Forecasts call for 1.9% load growth in 2026 and 2.5% in 2027 [20].
• Manufacturing reshoring — chip fabs and battery/EV plants (spurred by federal incentives) create large, electrically dense buildings.
• Electrification and the grid — solar/wind "balance-of-system," EV charging, and utility transmission all consume conduit and pole-line hardware.
• Residential construction and renovation — boxes, faceplates, and nonmetallic conduit; rate-sensitive but a large steady base.
• Replacement/MRO — maintenance and retrofit demand provides a floor beneath new construction.

Counterpoint: "grid investment" does not translate dollar-for-dollar into new hardware. Dynamic line ratings and other grid-enhancing technologies can increase capacity on existing corridors and defer physical expansion. DOE cites one deployment that increased line capacity by 6–14% while reducing infrastructure-investment needs [21].

7. Regulation

Regulation here is mostly about safety codes, product listing, and trade — not price or entry controls.

• National Electrical Code (NEC / NFPA 70). The installation code, updated on a three-year cycle and adopted by states and local jurisdictions, dictates wiring methods, where raceway is required, box-fill limits, and acceptable materials [22]. Code changes directly move product demand and mix.
• Third-party listing (UL, Intertek/ETL). Products generally must be tested and listed to a safety standard before inspectors will accept them. Relevant standards include UL 514A for metallic outlet boxes, UL 514B for fittings, UL 514C for nonmetallic boxes, and UL 6 for rigid steel conduit [2][23]. This is a real barrier to entry and to low-cost imports — a listing is expensive and slow to obtain.
• OSHA requirements. OSHA requires conductors entering boxes and fittings to be protected from abrasion and openings to be closed, and requires covers on pull boxes, junction boxes, and fittings — evidence that these products are safety-critical rather than decorative hardware [24].
• Buy America / Build America, Buy America (BABA). Domestic-content rules on federally funded infrastructure favor U.S.-made conduit and fittings, and some states add public-works procurement preferences.
• Trade remedies. Steel and aluminum tariffs (Section 232) raise input costs but also protect domestic producers; antidumping and countervailing-duty actions target imported conduit. This is an active battleground: after a surge in Mexican steel-conduit imports, Zekelman/Wheatland Tube closed a Chicago plant (≈237 jobs) in 2024 and pursued legal and trade actions, winning a 2025 Pennsylvania ruling restricting Mexican-made conduit in that state's public works [8][9].
• Workplace safety. BLS reported a 2024 total-recordable injury rate of 1.7 cases per 100 full-time-equivalent workers and a 1.0 DART rate for NAICS 335932 [25].

8. Competitive dynamics and consolidation

The top of the industry has consolidated steadily, while the commodity tail stays fragmented:

• ABB acquired Thomas & Betts in 2012, folding a leading conduit/fittings/box franchise into its Electrification arm [14].
• Atkore was built from Tyco's Allied Tube & Conduit and Unistrut, owned by private equity (Clayton, Dubilier & Rice), and went public in 2016 [4].
• nVent was spun out of Pentair in 2018, then reshaped its portfolio: it bought ECM Industries (~$1.1B, 2023) and utility-enclosure maker Trachte, and in January 2025 sold its Thermal Management business (Raychem, Tracer) to Brookfield for $1.7 billion to focus on enclosures and electrical connections [11][12].
• Nucor bought Republic Conduit (steel conduit) in 2017, giving a mega-cap steelmaker a downstream conduit position [9].

Judgment: expect more of the same — scaled players using M&A to add engineered, higher-margin systems (enclosures, cable management, grounding), while plain conduit remains a price- and import-driven commodity where scale, freight geography, and low-cost operations decide winners.

9. Risks

• Pricing-cycle / margin normalization. The single biggest risk. Peak-cycle conduit margins mean-revert as supply and imports return — Atkore's swing from 30.9% to 16.5% segment EBITDA margin in a single year is the case study [4].
• Construction cyclicality and rates. Nonresidential construction is interest-rate sensitive and was softening into 2025–26 [17].
• Import competition and trade dependence. Mexican steel-conduit and Asian fittings pressure domestic volume and price; the industry leans on tariffs and AD/CVD actions for protection [8][9].
• Input-cost volatility. Steel, PVC resin, aluminum, and HDPE prices swing margins and inventory values in both directions; tariffs cut both ways (protection vs. higher input cost). The commercial risk is the delay between cost movement and repricing: a manufacturer can lose margin during inflation if price increases lag, or during deflation if high-cost inventory must be sold into falling market prices.
• Material and method substitution. PVC, steel, aluminum, fiberglass, flexible conduit, armored cable, cable tray, and open-supported cable can compete where code and application permit. Corrosion, fire performance, electromagnetic shielding, physical protection, installation labor, and local code determine the winner. A producer concentrated in one material may lose share even if total electrical construction rises.
• Channel amplification. Distributor destocking/restocking exaggerates the underlying demand cycle.
• Concentration on the data-center theme. A pause in hyperscale capex would remove a major recent growth engine.
• Code and listing changes. Regulation is both moat and risk — code or listing changes can obsolete tooling, require retesting, or favor a substitute material.

10. How to invest, and the outlook

Public routes.

• Atkore (ATKR) — the closest thing to a pure U.S. conduit/raceway play; also the most exposed to the pricing cycle, so its share price, dividend, and earnings multiple move with commodity spreads.
• Preformed Line Products (PLPC) — the narrowest listed exposure to transmission and distribution line hardware; global footprint and also sells fiber closures, solar, and EV-foundation products.
• nVent (NVT) — engineered enclosures, cable management, and fastening; a cleaner "systems" growth profile.
• Hubbell (HUBB) — wiring devices and rough-in boxes inside a broader electrical/utility franchise.
• Diversified electricals — Eaton (ETN), ABB (ABB), Legrand (LGRDY), and steelmaker Nucor (NUE, via Republic Conduit) all carry meaningful noncurrent-carrying lines but dilute the exposure across much bigger businesses. Broad electrical-equipment and industrial ETFs offer indirect exposure.

Private routes. Much of the industry is not listed: Zekelman/Wheatland, Southwire, Cantex, Robroy Industries, IPEX/Aliaxis, Champion Fiberglass, Electri-Flex, plus a churn of private-equity-owned fabricators and regional plants. Access comes through direct acquisition, private-equity vehicles, or as a supplier/distributor into the channel. The attractive targets tend to possess required listings, specified brands, tooling, distributor relationships, and short-lead-time domestic production. The central diligence questions are SKU-level price-cost history, replacement cost of certifications and tooling, distributor concentration, true maintenance versus new-construction demand, inventory accounting through raw-material cycles, and how much revenue genuinely belongs to 335932. These businesses are typically valued on through-cycle EBITDA given the commodity swings.

Near-term outlook (judgment, not fact). The secular volume story is favorable: data centers, reshored manufacturing, electrification, and grid investment all raise the amount of conduit, boxes, and cable management per project, and Buy America rules plus trade actions tilt work toward domestic capacity. But the easy margin tailwind is gone — conduit pricing has normalized off its 2021–22 peaks, so returns from here depend on volume growth and cost discipline rather than windfall prices. The variables to watch are nonresidential construction and interest rates, steel and resin costs, the pace of data-center capex, and the next moves in conduit trade cases. For public-market investors that argues for underwriting mid-cycle economics; for private investors it favors the engineered, listed, spec-driven niches over plain commodity conduit.

---

Sources

1. U.S. Census Bureau, "2022 NAICS Manual — NAICS 335932 definition," 2022. https://www.census.gov/naics/reference_files_tools/2022_NAICS_Manual.pdf
2. UL Solutions, "Mechanical Support and Assembly Services (wiring device testing and certification)," 2025. https://www.ul.com/services/mechanical-support-and-assembly-services
3. Preformed Line Products Co., 2025 Form 10-K (principal inputs, revenue, margins), 2026. https://www.sec.gov/Archives/edgar/data/80035/000008003526000007/plpc-20251231.htm
4. Atkore Inc., Fiscal 2025 Form 10-K (segment results, business model, hedging policy), 2025. https://www.sec.gov/Archives/edgar/data/1666138/000162828025054049/atkr-20250930.htm
5. U.S. Census Bureau, 2022 Economic Census, Concentration Ratios and Product/Firm Statistics for NAICS 335932 (receipts, firm count, CR4/CR8/CR20/CR50, HHI), 2022. https://data.census.gov/
6. U.S. Census Bureau, County Business Patterns (CBP), NAICS 335932 (establishments, employment, annual and Q1 payroll), 2023. https://www.census.gov/programs-surveys/cbp.html
7. U.S. Small Business Administration, Table of Small Business Size Standards (NAICS 335932 = 1,000 employees), 2023. https://www.sba.gov/document/support-table-size-standards
8. Crain's Chicago Business, "Company that shut Chicago steel-conduit plant sues Mexico," 2024. https://www.chicagobusiness.com/manufacturing-logistics/company-shut-chicago-steel-conduit-plant-sues-mexico
9. Global Market Insights, "Residential Metal Electrical Conduit Market" (leading U.S. conduit producers and shares), 2025. https://www.gminsights.com/industry-analysis/residential-metal-electrical-conduit-market
10. NEMA, "2024 Guide to the Electroindustry" (warning on combined 335931/335932 tables), 2024. https://www.nema.org/docs/default-source/nema-documents-libraries/2024-guide-to-the-electroindustry.pdf
11. nVent Electric plc, 2024 Annual Report / Form 10-K (segments and revenue), 2025. https://www.sec.gov/Archives/edgar/data/1720635/000110465925030568/tm258500d3_ars.pdf
12. Yahoo Finance / nVent Electric, "nVent Completes Sale of Thermal Management Business to Brookfield for $1.7 billion," 2025. https://finance.yahoo.com/news/nvent-completes-sale-thermal-management-211500871.html
13. Hubbell Incorporated, 2025 Form 10-K (Electrical Solutions segment net sales, COGS composition), 2026. https://www.sec.gov/Archives/edgar/data/48898/000162828026007500/hubb-20251231.htm
14. ABB, "Installation Products (formerly Thomas & Betts): conduit, fittings, boxes, cable protection," 2025. https://electrification.us.abb.com/products/installation-products
15. Robroy Industries, "About / History," 2025. https://robroy.com/about/history
16. Aliaxis Middle East, "About Us (ownership structure)," 2025. https://aliaxis-me.com/en/about-us/about-us
17. ConstructConnect / AIA Consensus Construction Forecast, "Nonresidential construction and reshoring drivers, 2025," 2025. https://www.aia.org/resource-center/january-2025-consensus-construction-forecast
18. IndexBox / industry analyses, "Electrical conduit and cable-management demand: data centers and infrastructure," 2025. https://www.indexbox.io/blog/electrical-conduits-market-demand-to-accelerate-by-2035-amid-global-infrastructure-modernization/
19. U.S. Energy Information Administration, "Electric utility distribution and transmission capital expenditures, 2023," 2024. https://www.eia.gov/todayinenergy/detail.php?id=63724
20. U.S. Energy Information Administration, "Electricity demand growth and forecast, March 2026," 2026. https://www.eia.gov/TODAYINENERGY/detail.php?id=67344
21. U.S. Department of Energy, "Smart Transmission Tools Modernize America's Power Grid (grid-enhancing technologies)," 2025. https://www.energy.gov/cmei/systems/articles/smart-transmission-tools-modernize-americas-power-grid
22. National Fire Protection Association, "NFPA 70, National Electrical Code (NEC)," 2023 edition. https://www.nfpa.org/product/nfpa-70-code/p0070code
23. NEMA, "Conduit Fittings standards and product roster," 2025. https://www.nema.org/membership/products/view/conduit-fittings
24. OSHA, "1926.405 — Wiring methods, components, and equipment for general use," 2025. https://www.osha.gov/laws-regs/regulations/standardnumber/1926/1926.405
25. U.S. Bureau of Labor Statistics, "Table 1: Incidence rates of nonfatal occupational injuries and illnesses by industry," 2024. https://www.bls.gov/web/osh/table-1-industry-rates-national.htm