HVAC Electrical Insulation & EMI
H-O Products die-cuts and converts the electrical-insulation and EMI-shielding set inside HVAC equipment: flame-rated polypropylene phase barriers in the Formex™-class family, Nomex® aramid slot liners for blower and inducer motors, Kapton® polyimide dielectric layers, G10/FR4 and G11 capacitor-bank barriers, mica sheet for hot locations, and the nickel-graphite silicone gaskets, conductive foil tapes, and grounding pads that close the EMC story on a controls enclosure, built to your drawing.
Built for: VFD line- and load-side phase barriers, contactor and relay panel insulation, ECM and PSC blower-motor slot and layer insulation, EMI gasketing for VFD-dense controls enclosures, grounding and bonding pads, and capacitor and PFC bank barriers, supporting equipment designs evaluated to the customer's standards program, with every standard cited by designation.
To insulate and shield the electrical side of HVAC equipment, work job by job. VFD and motor-control phase barriers: flame-rated polypropylene barrier stock in the Formex™-class family (cited by family designation, UL 94 classes and CTI per the vendor TDS), die-cut Nomex® 410 where heat sits close, and Norplex FR4 (NP510) plate where the barrier must stay rigid.
Contactor and relay panel insulation: fish paper and PET film (family level) for economical liners, aramid insulation paper (Nomex®) near heat. Blower-motor slot and layer insulation: Nomex® 410/414 liners and wedges with Kapton® FN heat-sealable wraps, thermal-class context per IEC 60085 framing on the TDS.
EMI gasketing for controls enclosures: SSP502 nickel-graphite silicone, the SSP502-V0 series where a flame class rides along, and BISCO® EC-2130 soft conductive solid at low closure force, with emissions context per CISPR 11 and FCC Part 15 by designation. Grounding and bonding pads: conductive copper and aluminum foil tapes and BISCO® EC-2265 solid conductive silicone.
Capacitor and PFC bank barriers: G10/FR4 glass-epoxy, Norplex G11 (NP511), and muscovite mica where temperature crowds the laminates.
All standards by designation; values per the maker TDS on file; final material selection should be validated in the application. See the quote form for ordering details.
Panel-, equipment-, motor-, and EMC-level, by designation (the evaluation belongs to the customer's tested design or program): UL 508A (industrial control panels) · UL 60335-2-40 (heating and cooling equipment safety, successor context to UL 1995) · NEMA MG 1 (motors and generators, as motor-insulation design context) · IEC 60664 (insulation coordination for low-voltage systems) · CISPR 11 and FCC Part 15 (emissions frameworks behind VFD EMC work).
Material-level, per the maker TDS: UL 94 (flammability classes, including V-0 on the listed grades) · ASTM D149 (dielectric breakdown methods) · NEMA LI 1 (industrial laminate grade designations, G10/FR4/G11) · IEC 60085 (thermal class framework referenced on insulation TDSs).
- Folding phase barriers: Formex™-class flame-rated PP / Nomex® 410
- Rigid barrier plates: FR4 (NP510) / G11 (NP511)
- Panel liners on a budget: fish paper / PET film (family level)
- Slot & layer insulation: Nomex® 410 / 414
- Heat-sealable motor wraps: Kapton® FN
- Hot-location layers: ManniGlas® / muscovite mica
- EMI door & cover gaskets: SSP502 nickel-graphite / SSP502-V0
- Low-closure-force EMI seals: BISCO® EC-2130 sponge
- Seam bridging & ground paths: conductive foil tape
- Grounding contact pads: BISCO® EC-2265 solid
Where are you in the spec process?
This page serves engineers who already have insulation and EMI callouts on the drawing and engineers still deciding which family carries each job. Pick the path that matches where you are; you don't have to read the rest.
Send a drawing, get a quote
A barrier flat pattern, a Nomex® designation, a laminate grade, an EMI gasket profile, or a complete die-cut insulation and shielding kit on your drawing. Engineering reviews it against the maker TDSs and quotes it.
Skip to the quote form →Work the six jobs in order
Six numbered jobs from the VFD compartment out to the capacitor bank, each with engineering context, the material families that commonly carry it, and exactly what to put on the drawing.
Start with the VFD →
Where H-O parts do the work
Pick a job to see the exposure, the constraint, and the material families H-O converts for it.
VFD & motor-control phase barriers
Engineering context. The electrical heart of a modern rooftop unit, air handler, or chiller is its drive section: a variable frequency drive with 480 VAC three-phase on the line side, a switched PWM waveform on the load side, and contactor and overload hardware packed around it. Phase barriers separate input phases, isolate line from load, and stand between field-wiring lugs and the control wiring beside them.
The classic construction is a die-cut, scored, and folded flat pattern: a barrier that ships flat, folds into a channel or box at assembly, and holds its shape without fasteners. Control-panel work in this space is commonly framed by UL 508A practice (cited by designation; the panel evaluation belongs to the panel builder), and the spacing logic behind each barrier follows the equipment design's IEC 60664 insulation-coordination practice.
What H-O converts. Die-cut and scored flame-rated polypropylene barrier stock in the Formex™-class family, cited by family designation with flammability class, CTI performance, and dielectric data per the vendor TDS; Nomex® 410 barriers where thermal endurance drives the choice; and flat Norplex FR4 (NP510) barrier plates where the part must stay rigid across a span. Kiss-cut barrier sets ship on liner in assembly order for cabinet-level kitting through CNC knife cutting and kitting.
Material-family guidance. Flame-rated polypropylene barrier stock is the folding workhorse of this job: it scores and folds into self-supporting shapes, and the listed grades carry UL 94 V-0 classes per the vendor TDS [3], with comparative tracking index data that matters in the dusty, humid air a rooftop cabinet breathes. Aramid paper takes over where the barrier sits near heat sinks or braking resistors: Nomex® designations carry their thermal-class context per the maker TDS [5].
Glass-epoxy laminate is the rigid option where a barrier doubles as a mounting plate. Commonly specified by flat-pattern drawing with score lines called out; the fold radius and grain direction belong on the drawing, because a fold that fights the material is the most common barrier failure at assembly. Spacing decisions stay inside the equipment design's IEC 60664 practice [1].
Grade-level properties, standards and caveats for these families are in the material reference below — one card per family, with the TDS links.
The flat pattern with fold and score lines, material thickness, flammability class required on the part (UL 94 class per the vendor TDS), working temperature near the barrier, and quantities for prototype and production. If the barrier mounts with adhesive, note the substrate: adhesive performance depends on substrate, surface energy, temperature, exposure, dwell time, applied pressure, surface preparation, joint geometry, and the assembly process, and tape selections should be validated in the application.
Contactor & relay panel insulation
Engineering context. Around the drive sits the rest of the control section: contactor banks for compressors and fans, relays, terminal blocks, transformers, and the back panel everything mounts to. Its insulation work is quiet and constant: liner sheets behind back panels and subpanels, covers over terminal strips, separators between adjacent contactors, and insulating washers and spacers under hardware.
Contactors add their own concern, the switching arc, which puts a premium on materials that tolerate heat and do not track across a contaminated surface.
None of these parts is glamorous; all of them are the difference between a panel that passes its documentation review and one that collects field tickets.
What H-O converts. Die-cut vulcanized fibre (fish paper) and PET dielectric film liners, covers, washers, and spacers converted at the family level; aramid insulation paper (Nomex®) separators and covers where contactor heat sits close; muscovite mica sheet for arc-adjacent locations; and Kapton® HN film where a thin, thermally tough dielectric has to fit a gap budget measured in tenths of a millimeter.
Material-family guidance. Split the panel by stress. Fish paper and PET film carry the low-stress liners and covers economically, per the vendor TDS at the family level; where temperature, tracking, or mechanical load rises, the named families take over. Aramid paper holds its properties near switching heat, with dielectric methods per ASTM D149-class testing on the maker TDS [2].
Mica is the inorganic option beside arc chutes: thin, dimensionally stable at fault temperatures, and contributing no fuel. The panel-level framing is UL 508A practice, cited by designation [6]; the equipment-level framing for packaged units is UL 60335-2-40, also by designation [7]. The materials on this page support designs evaluated to those standards; the evaluation belongs to the panel builder or equipment maker.
Grade-level properties, standards and caveats for these families are in the material reference below — one card per family, with the TDS links.
Part geometry (a DXF is ideal), thickness, the working temperature at the location, any flammability class the panel documentation needs (per the vendor TDS), mounting method, and quantities. "Recommend the family" is a valid callout; the engineering review proposes one from the panel layout.
Slot & layer insulation for blower motors
Engineering context. HVAC moves air with motors: ECM and PSC blower motors in air handlers, draft-inducer motors on furnaces, condenser-fan motors on rooftops, and the compressor motors behind the refrigeration circuit. Their insulation is a layered system: slot liners between winding and stator core, phase insulation between winding groups, layer insulation between winding passes, wedges holding conductors in the slot, and wrappers over finished coils.
Every layer is specified by designation and thickness off the winding drawing, the insulation system's thermal class frames the materials that can live in it, and motor design practice is commonly framed by NEMA MG 1, cited here by designation as design context.
What H-O converts. Slit and Nomex® 410 slot liners, phase insulation, and layer insulation; Nomex® 414 where the higher-density grade suits the slot; Nomex® 818 pressboard for wedges and formed pieces; Kapton® FN heat-sealable polyimide for bonded wraps; and ManniGlas® glass-fiber paper where inorganic temperature endurance earns its place near hot spots. Narrow-width slitting and kitted winding sets run on slitting and flatbed die-cutting.
Material-family guidance. Aramid paper is the default for slot and layer duty: conformable, slittable to narrow widths, with thermal-class context per IEC 60085 framing on the maker TDS [5] and dielectric methods per ASTM D149-class testing [2]. Kapton® FN adds an FEP heat-seal layer for wraps that bond to themselves. Glass-fiber paper carries the hottest locations, draft-inducer duty among them.
The deep version of this playbook, across the full motor and transformer range, lives on the busbar, transformer & motor insulation sibling page; this section is its HVAC edition. Final material selection should be validated in the application against the insulation system's thermal class and the winding process.
Grade-level properties, standards and caveats for these families are in the material reference below — one card per family, with the TDS links.
The winding drawing or slot dimensions, material designation and thickness per layer, slit-width tolerances, any heat-seal or adhesive requirement, and the insulation system's thermal-class context. Slit-and-sheeted stock, liners, and kitted winding sets are all standard outputs.
EMI gasketing for controls enclosures
Engineering context. A VFD is a deliberate radio-frequency noise source: fast PWM edges couple onto motor leads, enclosure panels, and anything conductive nearby, and the building-automation controllers, wireless sensors, and communication buses living in the same cabinet are the first victims. The enclosure is the first line of EMC defense, and an enclosure shields only as well as its seams: every door, cover, and removable panel is a slot antenna until a conductive gasket closes it.
The regulatory framing is the emissions environment, commonly referenced through CISPR 11 and FCC Part 15 by designation; the EMC evaluation belongs to the equipment maker's tested design, and the gasket is the converted part that helps the design get there.
What H-O converts. Die-cut and strip-cut SSP502 nickel-graphite silicone door and cover gaskets; the SSP502-V0 series where the enclosure documentation also wants a flame class on the gasket (UL 94 class per the vendor TDS); BISCO® EC-2130 soft soft conductive solid silicone where sheet-metal doors close at low force; and the broader EMI shielding elastomer family for profiles the standard grades do not cover.
Material-family guidance. Pick by closure force first, conductivity second. Nickel-graphite silicone is the cost-effective conductive-elastomer default for HVAC enclosure work; the EC-2130 sponge construction trades some conductivity for a closure force that thin sheet-metal doors can actually deliver.
Galvanic pairing belongs on the drawing: a conductive gasket touches the enclosure metal by design, so note the mating finish (galvanneal, powder coat with masked lands, plated aluminum) and keep the pairing inside the corrosion guidance on the vendor TDS, particularly where the cabinet lives outdoors in condensing air.
The dedicated treatment of this family, fabric-over-foam and board-level options included, lives on the EMI shielding for switchgear, VFDs & racks sibling page; the parent EMI & EMC shielding application page carries the cross-industry overview.
Where the gasket is PSA-backed, the adhesive holds the part for assembly and the conductive path comes from compression: adhesive performance depends on substrate, surface energy, temperature, exposure, dwell time, applied pressure, surface preparation, joint geometry, and the assembly process, and tape selections should be validated in the application.
Grade-level properties, standards and caveats for these families are in the material reference below — one card per family, with the TDS links.
Gasket cross-section or groove dimensions, flange and door geometry, closure force available, mating-surface finish for galvanic pairing, the emissions context by designation (CISPR 11 / FCC Part 15) if the program names one, any flame-class requirement on the gasket, and the environment (indoor mechanical room vs. rooftop). Quantities for prototype and production close the loop.
Grounding & bonding pads
Engineering context. Every EMI strategy ends at the ground path. VFD installation practice wants low-impedance, high-frequency bonding between drive chassis, mounting plate, enclosure, and conduit, and a painted panel interrupts that path exactly where the drawing assumed it existed. The converter-side parts of this job are small and decisive: conductive contact pads under drive feet and ground lugs, foil-tape bridges across hinge lines and panel seams, and masks that keep powder coat off the lands where metal must meet metal.
A bonding strategy that lives only in the schematic fails at the first painted surface; one that is drawn as parts survives production.
What H-O converts. Die-cut conductive copper and aluminum foil tapes with conductive PSA, slit to width or as bonding straps and seam bridges; BISCO® EC-2265 electrically conductive solid silicone contact pads where a resilient conductive interface has to live under hardware; EC-2130 soft conductive solid where the joint needs more conformability than a solid pad gives; and masking shapes that protect grounding lands through the paint line, with surface-protection films handled on the same tooling.
Material-family guidance. Treat the foil tape as a manufactured electrical part, not shop tape: width, length, foil thickness, and adhesive system come off the drawing, and the conductive-PSA data on the vendor TDS is what the EMC reviewer will ask for. Conductive elastomer pads earn their place where vibration or repeated service would loosen a hard joint; they maintain contact through movement that would crack a soldered strap.
Galvanic pairing applies here too: copper against aluminum in a condensing rooftop environment is a documented-corrosion question, so name both metals on the drawing and keep the pairing inside the vendor guidance. And because every one of these parts bonds through an adhesive at assembly: adhesive performance depends on substrate, surface energy, temperature, exposure, dwell time, applied pressure, surface preparation, joint geometry, and the assembly process; tape selections should be validated in the application.
Grade-level properties, standards and caveats for these families are in the material reference below — one card per family, with the TDS links.
Pad and strap geometry, both mating metals and finishes, whether the joint sees vibration or service access, the masking outline if H-O is cutting paint masks, and the EMC program context by designation. Send the panel finish spec with the drawing; half of grounding-pad engineering is knowing what the surface really is.
Capacitor & PFC bank barriers
Engineering context. Two capacitor populations live in HVAC equipment, and both deserve barriers. Inside the VFD, the DC bus capacitor bank holds charge after power-down, and service practice puts insulating covers and barriers between technicians and the bus structure. At the equipment level, power-factor-correction banks and motor run/start capacitors cluster in their own compartments, where a failing can vents energetically and a barrier keeps the event local.
The insulation job combines dielectric duty with mechanics: covers that survive service handling, barriers that take fastener torque, and liners that keep clearances honest in a compartment that was sized before the capacitors grew.
What H-O converts. Machined and G10/FR4 glass-epoxy barrier plates and covers; Norplex G11 (NP511) where elevated temperature rides with the electrical duty; Durostone® composite laminate for structural insulating covers; muscovite and phlogopite mica sheet where inorganic behavior at fault temperatures is wanted on the same part; and fish paper / PET film liners for the low-stress surfaces between. Thick laminate sections cut clean on waterjet cutting.
Material-family guidance. The laminate grades are specified by NEMA LI 1 designation [4], with dielectric methods per ASTM D149-class testing on the maker TDS [2]; comparative tracking index feeds the material-group decisions in the equipment design's IEC 60664 spacing practice [1]. FR4 is the default; G11 steps in where the compartment runs hot; Durostone® where the cover is frankly structural; mica where the barrier sits beside stored energy and the design wants a layer that does not melt or contribute fuel.
A barrier that survives bolt torque without cracking is a mechanical spec as much as an electrical one, so fastener loads belong on the drawing next to the dielectric note.
Grade-level properties, standards and caveats for these families are in the material reference below — one card per family, with the TDS links.
Part geometry (DXF or STEP), laminate grade and thickness if chosen, required creepage dimension and material-group note from the equipment design, fastener loads, working temperature in the compartment, and quantities. H-O converts the parts to drawing; the insulation-coordination analysis itself stays with the equipment designer.
The decisions that drive an electrical-insulation & EMI spec
Insulation and EMI parts are chosen in order: the voltage and spacing, the temperature, and whether the part isolates or shields.
Decide whether the part isolates (dielectric) or grounds (conductive) first, then size it to the voltage, temperature, and documentation the review asks for. Grades carry their own dielectric and thermal class per TDS.
Show all 5 selection factors tap to expand
Specification Tools
Two tools to take you from "we're building an HVAC control section" to here's the insulation and EMI checklist for the drawing set: a job-driven checklist builder that assembles the layer list with its citation language, and a side-by-side comparison of every family on this page.
1. HVAC electrical insulation & EMI checklist builder
Check the jobs your design carries. The builder assembles the corresponding material layers into a checklist with the family, what to send with the drawing, and the citation language (material classes per the maker TDS; panel, equipment, motor, and EMC standards by designation). The default selection is pre-built for a typical VFD-equipped control section; every layer is also printed in the material reference section, so nothing here exists only behind a script.
Insulation & EMI checklist: 3 layers selected
Each checked job adds its layer below. The list is the starting bill of materials for the engineering review, not a certification: material classes (UL 94) come from the grade TDS, and panel, equipment, motor, and EMC standards (UL 508A, UL 60335-2-40, NEMA MG 1, IEC 60664, CISPR 11) are cited by designation with the evaluation belonging to the customer's tested design or program.
- Phase barriers: flame-rated PP (Formex™-class) or Nomex® 410Send: flat pattern with fold/score lines, thickness, flame class. Cite: UL 94 class and CTI per the vendor TDS.
- Panel insulation: fish paper / PET liners, Nomex® near heatSend: geometry, thickness, working temperature, mounting. Cite: properties per the vendor TDS at the family level.
- EMI gaskets: SSP502 nickel-graphite or EC-2130 spongeSend: cross-section, closure force, mating finish. Cite: emissions context per CISPR 11 / FCC Part 15 by designation.
2. Side-by-side: HVAC insulation & EMI family comparison
Every family called out on this page, with construction, the property that drives its selection, the standards its TDS cites, and the job it serves. Click a column header to sort. Click any material name to jump to its accordion entry.
| Material | Construction | Selection driver | Standards on the TDS / by designation | Job | |
|---|---|---|---|---|---|
| Films & papers (bend, wrap, fold, line) | |||||
| Flame-Rated Polypropylene Barrier Stock (Formex™-class)Family designation | Scored & folded PP sheet | Folds into self-supporting shapes | UL 94 classes & CTI per vendor TDS | VFD / motor-control phase barriers | |
| Nomex® Aramid Paper (410 / 414 / 818)Aramid designations | Calendered aramid paper | Thermal endurance, conformability | IEC 60085 thermal-class context; D149-class methods per TDS | Slot/layer insulation, hot barriers | |
| Kapton® HN / FN Polyimide FilmThin-gauge designations | Polyimide film | Thin, thermally tough dielectric | ASTM D149-class methods per maker TDS | Motor wraps, tight-gap dielectric | |
| Fish Paper / PET Dielectric Film (family level)Films, papers & laminates family | Vulcanized fibre / polyester film | Economical low-stress liners | Per vendor TDS at the family level | Panel liners, covers, spacers | |
| Laminates & inorganics (bear load, sit near energy) | |||||
| G10/FR4 & G11 Glass-Epoxy (NP510 / NP511); Durostone®NEMA LI 1 grades | Glass-epoxy laminate | Carries load; CTI-rated creepage duty | NEMA LI 1 designations; D149-class methods per TDS | Capacitor barriers, rigid plates | |
| Muscovite & Phlogopite Mica Sheet + ManniGlas®Inorganic grades | Mica laminate / glass-fiber paper | Inorganic; stable at fault temperatures | Per maker TDS, method named per grade | Arc-adjacent & hot locations | |
| Conductives (close the seams, bond the chassis) | |||||
| SSP502 Nickel-Graphite Silicone + SSP502-V0 + EC-2130 SpongeConductive elastomers | Filled silicone / soft conductive solid | Shielding at the available closure force | UL 94 on the V-0 grades per vendor TDS; emissions context per CISPR 11 / FCC Part 15 (by designation) | Enclosure door & cover EMI gaskets | |
| Conductive Foil Tape + BISCO® EC-2265 Solid Conductive SiliconeGrounding set | Cu/Al foil with conductive PSA / solid conductive silicone | Low-impedance bonding through joints | Per vendor TDS; pairing per galvanic guidance | Grounding pads, seam bridging | |
Skip ahead and request your engineering review now
If your drawing set already calls out a barrier flat pattern, an aramid designation, a laminate grade, or an EMI gasket profile, send it over for engineering review against the TDSs and the standards language.
Electrical-insulation & EMI failures you can prevent at spec
These failures surface as a dielectric flashover, a hot-spot breakdown, or an enclosure that fails emissions — all decided in the material callout.
Insulation and EMI parts sit in a safety- and compliance-critical path. Confusing isolation with grounding, or under-sizing creepage, is where these specs go wrong.
Show all 5 failure modes tap to expand
1. Insufficient creepage on a phase barrier
Fix — size the barrier to IEC 60664 creepage and clearance for the working voltage and pollution degree.
2. Elastomer where slot or layer insulation runs hot
Fix — use mica or MannIGlas® glass-fiber matched to the IEC 60085 thermal class.
3. A conductive gasket used as an insulator (or the reverse)
Fix — separate EMI grounding (conductive) from dielectric isolation and specify each explicitly.
4. Undocumented dielectric strength
Fix — specify dielectric per ASTM D149 and the grade TDS so the barrier clears the UL 508A review.
5. EMI leak at an unsealed enclosure seam
Fix — bond the seam with a conductive EMI gasket to hold CISPR 11 emission limits.
Material reference
Detailed notes for the families referenced on this page: the films and papers (flame-rated polypropylene barrier stock, Nomex® aramid, Kapton® polyimide, and the family-level fish paper and PET films), the laminates and inorganics (G10/FR4, G11, Durostone®, mica sheet, ManniGlas® glass-fiber paper), and the conductives (nickel-graphite EMI silicones with the EC-2130 sponge, and the foil-tape and EC-2265 grounding set).
Values are per the maker TDS on file for each grade with the method named; panel, equipment, motor, and EMC standards are cited by designation only, with the evaluation belonging to the customer's tested design.
H-O die-cuts, kiss-cuts, slits, scores, and kits every family to drawing.
Flame-Rated Polypropylene Barrier Stock (Formex™-Class Family)Folded phase & section barriers · UL 94 classes and CTI per vendor TDS · cited by family designation
Converted at the family level; properties per the vendor TDS for the selected grade. Where the barrier sits near heat, the aramid family takes over; final material selection should be validated in the application.
Nomex® Aramid Insulation Paper (410 / 414 / 818 Pressboard)Slot & layer insulation, hot barriers, separators · thermal-class context per IEC 60085 framing on the TDS
Specify designation, thickness, and slit-width tolerance. The full voltage-range version of this family's story lives on the busbar, transformer & motor insulation sibling page.
Kapton® HN / FN Polyimide FilmHeat-sealable motor wraps, tight-gap dielectric layers · dielectric methods per maker TDS
Specify gauge, geometry, and any heat-seal need. Die-cut edges replace field trimming, which is where most film-liner failures start.
Vulcanized Fibre (Fish Paper) & PET Dielectric Film (Family Level)Economical panel liners, covers & spacers · converted at the family level per vendor TDS
Commonly used for cost-driven liner duty; may be suitable depending on temperature and stress. Final material selection should be validated in the application.
G10/FR4 & G11 Glass-Epoxy Laminate (NP510 / NP511) + Durostone® CompositeCapacitor-bank barriers, rigid plates, covers · NEMA LI 1 grade designations
Specify grade designation, thickness, fastener loads, and working temperature. G11 steps in where the compartment crowds the FR4 ceiling; Durostone® where the part is frankly structural.
Muscovite & Phlogopite Mica Sheet + ManniGlas® Glass-Fiber PaperArc-adjacent locations, hot spots, capacitor compartments · inorganic
Edges, tabs, and tolerances come off the drawing, not the shear; a barrier earns its keep only if it covers the footprint and survives assembly handling.
SSP502 Nickel-Graphite Silicone + SSP502-V0 Series + BISCO® EC-2130 SpongeControls-enclosure EMI gaskets · UL 94 on the V-0 grades per vendor TDS
Pick by closure force first, conductivity second. The dedicated EMI playbook, fabric-over-foam and board-level options included, lives on the EMI shielding for switchgear, VFDs & racks sibling page.
Conductive Foil Tape (Cu / Al) + BISCO® EC-2265 Solid Conductive SiliconeGrounding pads, bonding straps, seam bridging · conductive PSA per vendor TDS
Treat foil tape as a manufactured electrical part: width, foil thickness, and adhesive system come off the drawing, and the conductive-PSA data is what the EMC reviewer asks for.
HVAC electrical insulation & EMI: engineer-grade FAQ
Ten of the questions we hear most from RTU, AHU, chiller, and HVAC controls teams. If your question isn't here, send a drawing or call, engineering picks up.
Are these insulation and EMI materials UL-listed for HVAC equipment?
Equipment and panel listings belong to the tested equipment, not to the materials inside it. What the materials on this page carry is their own documentation: flammability classes such as UL 94 V-0 on the listed grade TDSs, dielectric and conductivity data with the method named, and lot-code traceability. They support panels framed by UL 508A practice and equipment framed by UL 60335-2-40, both cited by designation.
H-O supplies converted layers and paperwork as an ISO 9001:2015 certified organization; the panel builder or equipment maker owns the evaluation. [3]
What is a phase barrier in a VFD or motor-control compartment, and what is it made of?
A die-cut, scored insulating sheet that folds into a channel, box, or cover at assembly, separating input phases, line from load, and field-wiring lugs from control wiring. The folding workhorse is flame-rated polypropylene barrier stock in the Formex™-class family, with UL 94 classes and CTI data per the vendor TDS; aramid paper takes over near heat, and FR4 plate handles spans that must stay rigid. [3]
Flame-rated polypropylene vs aramid paper vs glass-epoxy: how do I choose a barrier material?
By temperature and mechanics. Flame-rated polypropylene folds into self-supporting shapes and is the economical default at modest working temperatures. Aramid paper holds its properties near heat (thermal-class context per IEC 60085 framing on the maker TDS) and folds well but does not hold a crease as crisply. Glass-epoxy laminate is rigid, carries fastener loads, and serves where the barrier doubles as structure. Each family's flammability class and CTI come off its own TDS; final material selection should be validated in the application. [5]
What insulation goes inside an HVAC blower motor?
A layered system specified off the winding drawing: Nomex® 410 or 414 slot liners between winding and core, phase insulation between winding groups, layer insulation between passes, 818 pressboard wedges, and Kapton® FN heat-sealable wraps over finished coils, with ManniGlas® glass-fiber paper at the hottest locations. The insulation system's thermal class (IEC 60085 context on the maker TDSs) frames which materials can live in it, and motor design practice is commonly framed by NEMA MG 1, by designation. [5]
Why does a VFD enclosure need an EMI gasket?
Because the drive's fast PWM switching edges make the enclosure part of the EMC design, and an enclosure shields only as well as its seams: an ungasketed door or cover behaves like a slot antenna at the frequencies a drive generates. A conductive elastomer gasket (nickel-graphite silicone, or soft conductive solid at low closure force) closes the seam electrically as well as environmentally. The emissions framing is commonly CISPR 11 or FCC Part 15, cited by designation; the EMC result belongs to the equipment maker's tested design. [8]
Nickel-graphite solid vs soft conductive solid: which EMI gasket fits an HVAC cabinet?
Pick by closure force first. SSP502 nickel-graphite solid silicone is the cost-effective conductive-elastomer default where the door structure can compress it; the SSP502-V0 series adds a UL 94 V-0 class per the vendor TDS where the enclosure documentation wants one. BISCO® EC-2130 soft conductive solid trades some conductivity for a closure force thin sheet-metal doors can actually deliver. Either way, note the mating finish on the drawing so the galvanic pairing stays inside the vendor guidance, particularly on rooftop cabinets in condensing air.
How do I bond a VFD chassis through a painted panel?
Draw the path as parts: a paint mask that keeps powder coat off the bonding land, a conductive contact pad or foil-tape bridge across the joint, and hardware that clamps metal to metal. Conductive foil tapes with conductive PSA handle seam and hinge bridging; EC-2265 solid conductive silicone pads keep contact through vibration and service cycles.
Adhesive performance depends on substrate, surface energy, temperature, exposure, dwell time, applied pressure, surface preparation, joint geometry, and the assembly process; tape selections should be validated in the application.
What barriers go around a capacitor or PFC bank?
Rigid insulating plates and covers, usually G10/FR4 by NEMA LI 1 designation, stepping to G11 where the compartment runs hot and to Durostone® composite where the cover is structural, with mica sheet where the design wants an inorganic layer beside stored energy. Specify the grade, thickness, fastener loads, and the required creepage note from the equipment design's IEC 60664 practice; a cover that cracks under bolt torque is the most common failure in this job. [4]
Does H-O supply materials with UL 94 V-0 ratings?
Yes, materials are available with UL 94 V-0 ratings per the vendor TDS: the flame-rated polypropylene barrier grades, the SSP502-V0 EMI gasket series, and other listed grades across the families on this page. The class belongs to the listed material grade per its TDS; H-O converts the material and supplies the documentation, and does not independently certify materials. Name the required class on the drawing and the review confirms the grade carrying it. [3]
What should I put on the drawing set so the quote comes back right the first time?
By job: for phase barriers, the flat pattern with fold and score lines plus the flammability class; for panel insulation, geometry, thickness, and working temperature; for motors, the winding drawing with designations and slit tolerances; for EMI gaskets, the cross-section, closure force, and mating finish; for grounding parts, both metals and the masking outline; for capacitor barriers, the grade, thickness, fastener loads, and the required creepage note.
Plus quantities for prototype and production. "Recommend the family" is a valid callout: that is what the engineering review is for.
Glossary: terms used on this page
Quick reference for the drive, insulation, EMC, and standards terminology used throughout. Each entry links to the relevant standard or test method where applicable.
VFD (variable frequency drive)
The power-electronics controller that varies motor speed by synthesizing a PWM waveform. In HVAC it runs fans, pumps, and compressors for part-load efficiency, and it defines both the insulation problem (line/load barriers, DC bus) and the EMI problem (fast switching edges) of the modern control cabinet.
Phase barrier
An insulating sheet separating phases, sections, or field-wiring terminations inside power equipment. In HVAC gear it is typically a die-cut, scored flat pattern that folds into a self-supporting channel or box at assembly.
Creepage distance
The shortest path between two conductors along an insulating surface. Required creepage grows with working voltage, pollution degree, and material group per the equipment design's IEC 60664 [1] practice; barrier plates and liners lengthen the path where the layout cannot.
Clearance
The shortest distance between two conductors through air. Barriers placed between conductors force the air path around them, which is how a plate buys clearance in a crowded control section.
CTI (comparative tracking index)
A measure of an insulating material's resistance to surface tracking under contamination, reported on the maker TDS. CTI assigns the material group used in IEC 60664-based spacing tables: better tracking resistance permits shorter creepage for the same conditions, which matters in the dusty, humid air HVAC cabinets breathe.
IEC 60664 (by designation)
Insulation coordination for equipment within low-voltage systems: the framework that sets creepage and clearance from working voltage, pollution degree, overvoltage category, and material group, per [1]. It governs the equipment design; the materials on this page are what those decisions get built from.
UL 508A (by designation)
The standard for industrial control panels, per [6]. It frames the panel builder's spacing, barrier, and component practice; cited here by designation, with the panel evaluation belonging to the panel shop and its program.
UL 60335-2-40 (by designation)
The safety standard for electrical heat pumps, air conditioners, and dehumidifiers: the equipment-level framework succeeding UL 1995 for much of the packaged-HVAC space, per [7]. Cited by designation; the equipment evaluation belongs to the maker's tested design.
NEMA MG 1 (by designation)
The NEMA standards publication for motors and generators: the design framework behind motor insulation systems, thermal classes, and inverter-duty considerations. Cited here by designation as design context for the blower-motor insulation job; the motor evaluation belongs to the motor maker.
NEMA LI 1 / G10 / FR4 / G11
The industrial-laminate classification defining the glass-epoxy grades, per [4]. FR4 adds a flammability class to the G10 construction; G11 holds its mechanical properties at higher temperature. Specified by grade designation on the drawing.
UL 94 (per the grade TDS)
The flammability classification for plastic materials (HB, V-2, V-1, V-0, 5V classes), per [3]. The class belongs to the listed material grade per its TDS at the tested thickness; it is a material property, not an equipment listing.
Thermal class (IEC 60085 context)
The temperature classification framework for electrical insulation systems referenced on insulation TDSs, per [5]. The class attaches to the evaluated insulation system; individual material TDSs cite their thermal context within it.
Shielding effectiveness
The attenuation an enclosure or gasketed joint provides against electromagnetic energy, reported in dB on conductive-gasket TDSs under defined test conditions. A laboratory value measured on a fixture, not a field result: the installed joint's geometry, closure force, and surface condition govern what the cabinet actually achieves.
Galvanic pairing
The corrosion relationship between a conductive gasket's filler or a foil tape's metal and the enclosure surface it touches. Dissimilar pairings in condensing outdoor air corrode the very contact the EMC design depends on; name both metals on the drawing and keep the pairing inside the vendor TDS guidance.
CISPR 11 / FCC Part 15 (by designation)
Emissions frameworks for industrial, scientific, and medical equipment (CISPR 11) and for unintentional radiators in the US regulatory context (FCC Part 15), per [8]. Cited here by designation as the EMC context behind VFD enclosure work; the emissions result belongs to the equipment maker's tested design.
Last updated · Reviewed by H-O Products engineering (ISO 9001:2015 certified converter, Winsted, CT).
Standards, test methods & technical references
The standards, test methods, and maker technical data sheets cited throughout this page. Panel, equipment, motor, and EMC standards are cited by designation: they evaluate designs, panels, and programs, and the evaluation belongs to the customer's tested design. Standards editions current as of June 2026; verify against the publishing body before final spec. H-O converts materials tested to the material-level methods on the source maker's TDS; H-O does not certify systems or independently certify materials unless explicitly stated on the quote.
[1] IEC 60664 (by designation)
Insulation coordination for equipment within low-voltage supply systems: the framework behind creepage, clearance, pollution degree, and material-group decisions in the equipment design. Cited by designation; the analysis belongs to the equipment designer. webstore.iec.ch (IEC 60664-1)
[2] ASTM D149
Standard test method for dielectric breakdown voltage and dielectric strength of solid electrical insulating materials at commercial power frequencies. The method behind the dielectric values on the film, paper, and laminate TDSs cited on this page. store.astm.org (ASTM D149-25)
[3] UL 94 (per the grade TDS)
Standard for tests for flammability of plastic materials for parts in devices and appliances. Classes (HB through V-0 and 5V) attach to the listed material grade at the tested thickness per the maker TDS; they are material properties, not equipment listings. ul.com/services/combustion-fire-tests-plastics
[4] NEMA LI 1 (by designation)
NEMA standards publication for industrial laminating thermosetting products: the grade-designation system (G10, FR4, G11, and related grades) used to specify the glass-epoxy laminates on this page. Cited by designation, by name only.
[5] IEC 60085 (by designation)
Electrical insulation: thermal evaluation and designation. The thermal-class framework referenced on aramid and film insulation TDSs; the class attaches to the evaluated insulation system. webstore.iec.ch (IEC 60085)
[6] UL 508A (by designation)
Standard for industrial control panels: the framework behind panel-shop spacing, barrier, and component practice for HVAC control sections. Cited by designation, by name only; the panel evaluation belongs to the panel builder and its program.
[7] UL 60335-2-40 (by designation)
Standard for the safety of electrical heat pumps, air conditioners, and dehumidifiers: the equipment-level safety framework succeeding UL 1995 for much of the packaged-HVAC space. Cited by designation, by name only; the equipment evaluation belongs to the maker's tested design.
[8] CISPR 11 / FCC Part 15 (by designation)
Emissions frameworks for industrial, scientific, and medical radio-frequency equipment (CISPR 11) and for unintentional radiators in the US regulatory context (FCC Part 15). Cited by designation, by name only, as the EMC context behind VFD enclosure shielding and bonding work; the emissions result belongs to the equipment maker's tested design.
Updated . Standards editions and links current at publication; verify against the publishing body before final spec. H-O converts materials tested to the methods cited; H-O does not certify systems. Lot-specific documentation available on request.
Get an HVAC insulation & EMI engineering quote
Send a drawing set, flat pattern, or winding drawing. We typically respond within one business day with a material recommendation, prototype lead time, and TDS verification against your flammability classes, dielectric requirements, EMC context, and standards language.
See also: related H-O application pages
Engineering content for the adjacent insulation and EMI sub-applications, the parent application, and the owning industry hub. Each page covers material selection, failure modes, and converter-side process detail for its application family.
Sibling sub-application
Busbar, transformer & motor insulation
The full laminate, mica, aramid, and film story this page's motor and barrier jobs draw from, across the voltage range.
Read the page
Sibling sub-application
Smart HVAC, IoT & electronics
Thermal, sealing, and dielectric parts for HVAC sensors, controllers, and connected IoT modules.
Read the page
Sibling sub-application
HVAC fire & high-temp protection
High-temperature and flame-resistant barriers for HVAC heat sources and electrical compartments.
Read the page
Sibling sub-application
Power electronics & drive insulation
The dielectric-and-TIM playbook inside the drive itself, at inverter and converter scale: insulating thermal pads, module barriers, and bus structures.
Read the page
Sibling sub-application
EMI shielding for switchgear, VFDs & racks
The dedicated EMI playbook behind this page's gasket and grounding jobs: conductive elastomers, foil tapes, and ground-contact hardware.
Read the page
Application overview
EMI & EMC shielding
The cross-industry shielding overview: gasket families, seam strategy, and the conductive-material catalog this page's EMI jobs draw from.
Read the page
Industry hub
Industrial HVAC
The full HVAC application family: sealing, vibration, thermal, electrical, fire protection, and the converter-side process detail behind each.
Read the page
Parent application
Energy, power & high voltage
The cross-industry power overview: insulation systems, creepage logic, and the material catalog this page's jobs draw from.
Read the page
Send the drawing set for your HVAC insulation & EMI parts
Barriers, liners, slot insulation, EMI gaskets, grounding pads, and capacitor-bank covers, in Winsted, Connecticut with material traceability and lot-code TDS records. Typical response in one business day.
Material data & standards. All dielectric, thermal, flammability, and conductivity values on this page are taken from the source maker's technical data sheets with the method named (ASTM D149-class dielectric methods, UL 94 classes per the listed grade TDSs, NEMA LI 1 grade designations, shielding and conductivity data per the vendor TDSs).
Panel, equipment, motor, and EMC standards (UL 508A, UL 60335-2-40, NEMA MG 1, IEC 60664, IEC 60085, CISPR 11, FCC Part 15) are cited by designation only: they evaluate designs, panels, and programs, the evaluation belongs to the customer's tested design, and the materials on this page support designs evaluated to them.
Performance depends on grade, geometry, compression, adhesive system, and environment; final material selection should be validated in the application. H-O converts materials; H-O does not build control panels, perform insulation coordination or EMC analysis, or certify systems, and does not independently certify materials against the standards unless explicitly stated on the quote. Verify against the maker TDS and your equipment-level evaluation plan.
Conversion scope. H-O and converts sheet, roll, and laminate stock to drawing in Winsted, Connecticut: die-cut and scored barrier flat patterns, slit films, papers, and foil tapes, waterjet-cut thick laminate sections, kiss-cut gasket sets on CNC knife cutting, and kitted insulation and EMI sets, with material traceability and lot-code TDS records. H-O does not mold or extrude in-house; molded or extruded profiles are coordinated through a partner network.
Lead-time and MOQ details are in the quote form above. Renderings and diagrams on this page are representative illustrations, not product photographs.