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Last updated: April 8, 2026

Quick Answer: Yes, you can generally put BX cable (also known as Armored Cable or AC cable) in a plastic electrical box, provided the box is rated for the application and you use the appropriate connectors. Standard PVC or thermoplastic electrical boxes are commonly used with BX cable. The critical factor is ensuring a secure and code-compliant connection between the BX cable's metal armor and the plastic box.

Key Facts

BX cable (AC cable) can be installed in plastic electrical boxes.
Appropriate BX connectors designed for plastic boxes are essential.
The metal armor of the BX cable must be properly grounded through the connector.
Plastic boxes must be UL-listed and suitable for the type of installation.
Local electrical codes may have specific requirements for using BX cable with plastic boxes.

Overview

The question of whether BX cable can be housed within a plastic electrical box is a common one for electricians and DIYers alike. Historically, BX cable, also known as Armored Cable (AC), was predominantly used with metal boxes. This was partly due to its construction, which features a flexible metal conduit encasing insulated conductors, and the traditional grounding methods that relied on the metal armor and box. However, modern electrical codes and materials have evolved, allowing for more flexibility. The key to a successful installation lies in understanding the specific requirements for connectors and ensuring proper grounding and mechanical protection of the cable within the plastic enclosure.

Plastic electrical boxes, often made from polyvinyl chloride (PVC) or other thermoplastics, have become increasingly popular due to their cost-effectiveness, ease of installation, and resistance to corrosion. When combining these with BX cable, careful attention must be paid to the method of connection. The BX cable's armor provides inherent grounding properties, and this grounding must be maintained when transitioning to a plastic box, which itself is not conductive. Therefore, the connector plays a pivotal role in bridging this gap and ensuring electrical safety.

How It Works

Connector Type is Crucial: The primary mechanism for connecting BX cable to a plastic box is through a specialized connector. These connectors are designed to grip the metal armor of the BX cable and provide a threaded or clamp-on interface that securely attaches to the plastic box. Importantly, these connectors are engineered to establish a continuous ground path from the BX cable's armor to the box. Standard metal BX connectors designed for metal boxes will not work directly with plastic boxes and may not provide the necessary grounding. Look for connectors specifically labeled for use with plastic boxes.
Grounding Through the Connector: The metal armor of BX cable acts as an equipment grounding conductor. When using a proper connector with a plastic box, the connector physically bites into or clamps onto the armor, creating a robust electrical connection. This connection then transfers the ground to the box's mounting system or a dedicated ground screw within the box, ensuring that any fault current has a safe path to ground. Without this proper grounding through the connector, the safety benefits of the BX cable's armor are negated.
Mechanical Protection: BX cable offers a degree of physical protection to the insulated conductors within its metallic sheath. When installed in a plastic box, the box itself must also provide adequate mechanical protection for the wires. Plastic boxes are generally designed to protect wiring from minor impacts, but care should still be taken during installation to avoid crushing or damaging the cable where it enters the box. The BX connector helps secure the cable and prevent it from being pulled or chafed.
Code Compliance: Electrical installations must adhere to local and national electrical codes, such as the National Electrical Code (NEC) in the United States. The NEC outlines specific requirements for the types of boxes, cables, and connectors that can be used together. While the NEC permits the use of AC cable in non-metallic boxes under certain conditions, it emphasizes the need for proper grounding and that all components must be listed by a recognized testing laboratory (like UL) for the intended application. Always consult the latest edition of your local electrical code and the product listings of the components you are using.

Key Comparisons

Feature	BX Cable in Plastic Box	BX Cable in Metal Box
Grounding Method	Relies on specialized connector to bond armor to box	Direct bond between armor and box, often with a grounding locknut
Connector Requirement	Specific BX connectors for plastic boxes with grounding provisions	Standard BX connectors (metal to metal contact)
Corrosion Resistance	Plastic box is corrosion-resistant; cable armor can still corrode in harsh environments	Metal box can corrode in damp or corrosive environments
Installation Ease	Plastic boxes can be lighter and easier to cut; connector installation is key	Metal boxes can be heavier; cutting and finishing edges requires care
Cost	Generally more economical due to plastic box and potentially simpler connectors	Can be more expensive, especially for heavier-duty metal boxes
Durability	Plastic boxes can be brittle under severe impact; BX armor provides protection	Metal boxes offer superior impact resistance

Why It Matters

Safety: The primary concern is electrical safety. Improperly grounded wiring is a significant fire hazard and increases the risk of electric shock. Using the correct connectors for BX cable in plastic boxes ensures that the grounding path is maintained, protecting occupants and property. A failure in this regard could lead to dangerous situations where metal parts of appliances or the electrical box itself become energized during a fault.
Code Adherence: Following electrical codes is not just a recommendation; it's a legal requirement. Building inspectors will verify that installations meet these standards. Correctly installing BX cable in plastic boxes ensures your work is compliant, avoiding costly rework and potential legal issues. Non-compliant installations can also impact insurance claims.
Longevity of Installation: A properly installed system, whether using plastic or metal boxes, will be more reliable and last longer. This means fewer callbacks for the installer and a safer, more dependable electrical system for the end-user. The mechanical integrity provided by the BX connector and the box's ability to secure the cable contribute to a stable, long-term installation.

In conclusion, the use of BX cable within plastic electrical boxes is permissible and common practice, but it hinges entirely on the correct selection and installation of specialized connectors. These connectors are the linchpin, ensuring that the essential grounding function of the BX cable's armor is effectively transferred to the plastic box, thereby maintaining electrical safety and code compliance. Always prioritize using UL-listed components and consult with local electrical codes to ensure your installations meet all necessary standards.