Custom Building Electrical Insulation, Phase Barriers & Enclosure Gaskets

No, and no honest supplier will say otherwise. "Arc-rated" describes tested PPE (an arc rating in cal/cm²) and, in the assembly sense, tested equipment; it is never a property of a raw sheet. Arc-flash protection is the result of an arc-flash risk assessment under NFPA 70E, driven by system voltage, available fault current, equipment type, and clearing time, none of which a material possesses.

What a barrier legitimately carries is its own material-level documentation: a UL 94 flame class, a dielectric strength per ASTM D149, a thermal class, and a comparative tracking index, all on the maker TDS. The barrier supports gear whose arc-flash protection lives with the assembly and your facility program; H-O supplies the converted layers and the paperwork. [1]

By duty. Fish paper (vulcanized fibre) is the economical, foldable deadfront, cover, and wireway-liner barrier at low voltage (~400 V/mil at thin gauge, UL 94 HB). Polyester (PET) film is the thin flexible barrier when you want more dielectric than fish paper without stepping to polyimide. Mica is the non-carbonizing, high-temperature phase barrier where a surface can be contaminated or hot, because it cannot track.

FR4 glass-epoxy is the rigid, load-bearing phase barrier that also braces the bus and is UL 94 V-0. Choose on four numbers, dielectric strength, tracking resistance (CTI), flame class, and thermal class, all per the grade TDS. [7]

Die-cut insulation goes in wherever air clearance alone is not enough to hold the working voltage: phase-to-phase and phase-to-ground barriers around the bus, and a deadfront insulation layer behind the cover a worker touches. The barrier families are mica or FR4 where a surface can be contaminated or the barrier must brace the bus, and fish paper or polyester film for the economical deadfront and cover duty, with Nomex® 410 where a 220 °C class is needed near lugs.

The checklist builder on this page assembles the layer list; the working voltage, the creepage target, and the room environment fill in the numbers. [2]

Both are woven-glass / epoxy laminates (NEMA LI 1 grades) with similar dielectric strength (roughly 485 V/mil for G10 and 635 V/mil for FR4 by ASTM D149) and similar mechanical strength, so both make good rigid, load-bearing phase-barrier plates and standoffs. The defining difference is flame class: FR4 is a flame-retardant, self-extinguishing grade at UL 94 V-0, while plain G10 is UL 94 HB.

If the location requires a flame class, specify FR4; if it does not and you want G10's slightly different properties, plain G10 is fine. Both are cited by their material class per the grade TDS. [14]

Because mica is inorganic and does not carbonize. Many organic insulators, under repeated surface discharge across a contaminated film, carbonize into a permanent conductive track, and once a track forms the barrier has failed. Mica cannot form that track, and it holds its dielectric strength to far higher temperatures (muscovite to ~500 °C, phlogopite higher), so it is the barrier of choice where a surface is contaminated or hot and the consequence of a track is a flashover.

Where the surface is clean and cool, an organic film is often the better economic choice; the decision is the surface environment and the temperature, not the sticker price. [13]

Nomex® 410 is a UL-recognized 220 °C insulation material (that recognition belongs to DuPont as the material maker, not to a converter). It keeps meaningful dielectric strength at temperature, holding roughly 300 V/mil for hours at 400 °C per its TDS, and its room-temperature AC rapid-rise dielectric strength runs from about 430 V/mil at 2 mil up to about 830 V/mil in the mid gauges.

That thermal retention is exactly why you step up from fish paper (a 115 °C class) to Nomex® near lugs, terminations, and control transformers. Specify the gauge to the voltage; DuPont recommends keeping continuous working stress under about 40 V/mil to limit corona. [11]

Comparative tracking index (CTI) is the maximum voltage at which a material withstands 50 drops of contaminated water without forming a conductive track, per IEC 60112. A higher CTI means the material resists surface tracking better, which lets you use a shorter creepage distance. In a dusty, sometimes damp electrical room, pick a high-CTI barrier (Formex-class flame-retardant polypropylene is rated CTI 600 V) where an organic sheet is acceptable, or specify inorganic mica, which cannot track at all.

Creepage (the distance along the surface) and clearance (the distance through air) are set by the working voltage, the pollution degree, and the material CTI, on the IEC 60664-1 basis. [19]

EPDM foam is the economical default for a NEMA Type 12 dust-tight door gasket, with a compression class per ASTM D1056 and flame-retardant V-0 grades available. Move to closed-cell silicone foam when a wide temperature range or a flame class drives the joint, since silicone foam is available UL 94 V-0 and runs from about −55 to +200 °C.

Either way, match the gasket's compression class to the real door closure force so the seal neither bottoms out nor stays loose; a failed gasket lets in the dust and moisture that degrade the insulation inside. The full enclosure-sealing playbook is on the building-envelope-sealing sibling page. [9]

No. H-O is a die-cutting converter: we supply the dielectric barriers, insulators, and gaskets to your drawing, with the material TDS, a certificate of conformance, and lot-code traceability, as an ISO 9001:2015 certified organization. We do not design, test, list, or arc-rate the equipment assembly, and we do not run your incident-energy study. The assembly listing belongs to the equipment maker (the OEM that builds and lists the panelboard, switchboard, or MCC), and the arc-flash program belongs to your facility under NFPA 70E.

Our documentation is the material-level evidence that supports those; the certifications and listings are theirs. [1]

We supply converted material components, not firestop listings. Where conduit or cable penetrates a fire-rated wall or floor of an electrical room, NEC 300.21 requires the opening be firestopped, and the fire rating is a property of the complete tested firestop system (UL 1479 / ASTM E814), a specific combination of barrier, penetrant, annular space, and listed materials, not of any single loose product.

H-O can and convert non-combustible component materials such as glass-fiber paper for use near penetrations and hot surfaces, but the firestop system and its rating stay with the tested assembly and its installer. Treat these as fire-barrier-adjacent materials, never as a rated firestop on their own. [2]

Die-cut barriers between the bucket compartment and the vertical bus, and between adjacent compartments, so a starter is isolated from the bus and a fault in one compartment does not walk into the next. The families are rigid FR4 glass-epoxy where the barrier takes the mechanical duty of bucket insertion, glass-filled polyester and fish-paper sheet where a flexible barrier suits, and mica where a compartment runs hot.

The edge and fit matter because the barrier has to survive repeated racking without shifting into a clearance. On this page the MCCs are the building-side lineups in mechanical and electrical rooms; the OEM that lists the MCC as an assembly owns its internal-arc qualification. [5]

By part: for a phase or deadfront barrier, the working voltage, the creepage and clearance target, the location (panelboard, switchboard, MCC, deadfront, wireway), any flame-class and thermal-class requirement, and the gauge and footprint; for an enclosure gasket, the door closure force, the gap, the NEMA type, and any flame class. Plus quantities for prototype and production, and the standards language you need on the paperwork (material classes per TDS; the arc-flash program and any assembly listing stay with the gear and the facility).

"Recommend the barrier" is a valid callout, that is what the engineering review is for. Attach the drawing or a sample part and we come back with a manufacturable option and the TDS.