When it comes to residential and light commercial wiring in the United States, NM-B cable and Romex are two of the most frequently discussed terms. Many homeowners, contractors, and even new electricians often ask: "Is NMB the same as Romex?" At first glance, the two may look identical, but there are some technical and brand-related details that need clarification.
This article will provide a comprehensive explanation of what NM-B cable is, what Romex means, their similarities, differences, common applications, and-most importantly-how to choose the right NM-B cable model for your specific project.
What is NM-B Cable?
NM-B stands for Non-Metallic Sheathed Cable, Type B. It is one of the most common electrical wires used in indoor residential wiring. The "B" designation indicates that the cable comes with a 90°C rated insulation on the conductors.
Key Features:
- Sheath Material: PVC outer jacket
- Conductors: Typically copper
- Insulation: Heat-resistant thermoplastic (90°C rating)
- Ground Wire: Bare or green insulated grounding conductor
Typical Uses:
- Lighting circuits
- Outlets in bedrooms, living rooms, and kitchens
- Indoor residential wiring protected by walls, ceilings, or floors
What is Romex?
Romex is not a technical wire type, but a brand name owned by Southwire Company. Over time, the name "Romex" has become a generic term used in the U.S. for NM-B cable.
In other words:
- All Romex is NM-B cable.
- Not all NM-B cable is Romex.
Several manufacturers produce NM-B cable, and Romex is simply the most widely recognized brand.
The Relationship Between NM-B and Romex
The relationship can be summarized as follows:
- NM-B = Cable Type (industry standard)
- Romex = Brand (produced by Southwire)
So when someone says "Romex wire," they usually mean NM-B cable, but they might specifically be referring to Southwire's version.
Similarities Between NM-B and Romex
- Both are non-metallic sheathed cables used indoors.
- Both contain copper conductors with thermoplastic insulation.
- Both comply with UL standards for residential electrical wiring.
- Both are available in the same common sizes (14/2, 12/2, 10/2, 12/3, etc.).
Differences Between NM-B and Romex
While they are largely interchangeable, a few subtle differences exist:
| Aspect | NM-B (Generic) | Romex (Brand) |
|---|---|---|
| Definition | Cable type (industry standard) | Trademarked brand by Southwire |
| Market | Produced by multiple manufacturers | Produced only by Southwire |
| Jacket Printing | May vary by manufacturer | Always carries Romex branding |
| Price | Slightly lower (in many cases) | Sometimes priced higher due to brand recognition |
Common Specifications & Applications
NM-B (including Romex) comes in different conductor sizes and combinations. Below are the most common ones:
| Specification | Ampacity | Typical Application |
|---|---|---|
| 14/2 NM-B | 15A | Lighting circuits, bedrooms, living rooms |
| 12/2 NM-B | 20A | Kitchen outlets, garage wiring, small appliances |
| 10/2 NM-B | 30A | Water heaters, A/C units, clothes dryers |
| 8/3 NM-B | 40A | Electric ranges, subpanels |
| 6/3 NM-B | 55A | Central air conditioning, heavy equipment |
How to Choose the Right NM-B Type
Selecting the right NM-B model is critical for safety and efficiency.
Practical Guidelines:
1.Check Ampacity Needs – Match the cable size with the breaker rating and the load requirement.
2.Match to Environment – NM-B is for dry, indoor use only (not rated for outdoor exposure).
3.Number of Conductors – Choose between /2 (2 conductors + ground) or /3 (3 conductors + ground) depending on single-phase or multi-phase requirements.
Example Scenarios:
1.Bedroom Lighting Circuit: A 15-amp breaker with standard lights → 14/2 NM-B.
2.Kitchen Small Appliance Circuit: Requires 20 amps → 12/2 NM-B.
3.Electric Water Heater: 30-amp load → 10/2 NM-B.
4.Electric Range with 240V Supply: Requires two hots + neutral + ground → 8/3 NM-B.
5.Central A/C Unit: High power demand → 6/3 NM-B.
Returning to the Theme: Is NMB the Same as Romex?
To answer directly: Yes, NM-B and Romex refer to the same type of cable, but Romex is simply the brand name. Functionally, Romex is a form of NM-B cable, but in the electrical industry, both terms are used interchangeably.
Choosing the Right Product for Your Project
When deciding between NM-B and Romex:
- If you prefer a well-known U.S. brand, you may choose Romex.
- If you need cost-effective yet UL and cUL certified NM-B cables, you can choose from other manufacturers like Greater Wire, which also guarantees full compliance with safety standards.
The important factor is not the brand, but whether the cable type, size, and certification meet your project requirements.
Partner With a Global Cable Manufacturer
At Dongguan Greater Wire & Cable Co., Ltd., we don't just supply NM-B cables-we provide complete wiring solutions.
- Comprehensive Range: From 14/2 to 6/3 NM-B cables, as well as THHN, XHHW, UF-B, and MC cables.
- International Certifications: All products are UL and cUL certified, ensuring compliance in both U.S. and Canadian markets.
- Flexible Supply: Whether you are a wholesaler, distributor, or contractor, we can meet orders of any size.
- Professional Support: Our team provides technical guidance, fast delivery, and responsive after-sales service.
🌎 No matter where your project is located,residential, commercial, or industrial.we are committed to delivering safe, reliable, and cost effective cable solutions.
📞 Contact Us Today
Dongguan Greater Wire & Cable Co., Ltd.
Tel/WhatsApp/Wechat: +86 135 1078 4550 / +86 136 6257 9592
Email: manager01@greaterwire.com