UL 44 Cable
UL 44 Cable refers to wires and cables covered by UL 44, Thermoset-Insulated Wires and Cables. This standard applies to electrical conductors with thermoset insulation and covers a range of wire types used in power distribution, building wiring, switchboards, and other electrical installations. Common types include RHH, RHW, RHW-2, XHHW, XHHW-2, and SIS wire.
UL 44 is important because it provides a consistent framework for key cable characteristics, including conductor construction, insulation, voltage rating, temperature rating, and suitability for wet or dry locations, depending on the specific wire type. This helps engineers, contractors, distributors, and buyers identify a wire that matches the requirements of a particular electrical installation.
The designation of each wire type provides useful information about its intended characteristics. For example, RHW-2 and XHHW-2 are commonly rated for 90°C in both wet and dry locations, while RHW and XHHW have different wet-location ratings. SIS wire is commonly used for internal wiring in switchboards and electrical panels.
When choosing a UL 44 cable, it is important to look beyond the standard name. The right product depends on factors such as voltage, conductor material and size, temperature rating, installation environment, and application. UL 44 provides the product requirements, while the actual installation should also follow the applicable electrical codes and project specifications.
UL 44 Cable Testing and Performance Requirements
UL 44 includes a series of performance requirements used to evaluate the safety, reliability, and suitability of thermoset-insulated wires and cables. The requirements cover both electrical and physical characteristics. The specific requirements may vary according to the cable type, construction, voltage rating, and intended application.
| Test / Evaluation Area | What It Evaluates | Why It Matters |
| Conductor Requirements | Conductor material, size, construction, and electrical characteristics | Helps ensure the conductor can deliver the required electrical performance |
| Insulation Performance | Insulation integrity and electrical insulating properties | Helps prevent insulation failure and unwanted current leakage |
| Dielectric Withstand | Ability of the insulation system to withstand specified electrical stress | Provides a basis for evaluating insulation reliability under electrical conditions |
| Insulation Resistance | Resistance of the insulation against current leakage | Helps assess the effectiveness of the insulation system |
| Physical Properties | Strength and other relevant physical characteristics of insulation materials | Helps ensure the insulation remains suitable during handling and service |
| Heat Resistance | Performance of insulation under specified temperature conditions | Supports the cable’s designated temperature rating |
| Environmental Performance | Applicable performance under conditions such as wet or dry locations | Helps ensure the selected wire is suitable for its intended installation environment |
| Flame and Safety Requirements | Applicable fire and safety characteristics | Helps reduce risks associated with electrical wiring installations |
UL 44 Cable
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Frequently Asked Questions
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Continuous Operating Rating: Standard UL 44 wires are rated for 75°C (167°F) or 90°C (194°F) continuous operation. Types ending with “-2” (such as XHHW-2 and RHW-2) maintain a 90°C rating in both wet and dry environments.
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Emergency Overload Rating: Up to 130°C (266°F) for short-term thermal overload conditions.
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Short-Circuit Rating: Maximum temperature tolerance up to 250°C (482°F) before structural insulation failure occurs.
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UL 44 (Thermoset Wires and Cables): Focuses on individual single-conductor or multiconductor wires insulated with thermoset polymers (XLPE or EPR). It covers conductors used primarily in conduits, raceways, and internal equipment wiring (such as XHHW-2, RHW-2, and SIS).
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UL 854 (Service-Entrance Cables): Covers complete cable assemblies specifically manufactured for main power service entry (Type USE, USE-2, SER, and SEU). While UL 854 cables often use UL 44-certified insulated conductors inside, UL 854 governs the overall cable construction, outer jackets, ground/neutral configurations, and direct-burial ratings required to link utility lines to main service panels.
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Scope and Voltage: Covers single- and multiple-conductor thermoset-insulated power and lighting cables rated for 600V, 1000V, and 2000V under the National Electrical Code (NEC / NFPA 70).
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Insulation Requirements: Specifies performance rules for cross-linked polyethylene (XLPE) and ethylene propylene rubber (EPR) insulation, ensuring the material will not melt or flow under excessive thermal stress.
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Product Line Coverage: Governs common industrial wire types including XHHW, XHHW-2, RHH, RHW, RHW-2, and SIS switchboard wire.
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Application Scope: Covers power distribution, main feeder circuits, branch wiring, industrial plant connections, and control cabinet/switchgear internal wiring.
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