NMD90 vs AC90 Cable: What's the Difference and Which Do You Need?
NMD90 is the common non-metallic indoor cable; AC90 (BX) is flexible metal-armoured cable for where mechanical protection is needed. Here's how they differ, where each is used, and what to check before buying.
Quick Answer
Use NMD90 for concealed, dry, indoor residential wiring. Use AC90 (BX) where you need a flexible armoured cable — exposed locations or where mechanical protection is required. Always confirm the cable type against your application, location, and the Canadian Electrical Code.
Who This Guide Is For
Electricians, apprentices, builders, and renovators choosing residential/commercial cable.
What They Are
- NMD90: non-metallic-sheathed cable; copper conductors in a plastic jacket; dry, concealed
indoor use (e.g., inside walls).
- AC90 (BX): armoured cable; conductors inside a flexible spiral metal jacket; used where
mechanical protection or an exposed run is needed.
Canadian Safety / Approval Notes
This guide is for product education and project planning only. Cable type, location ratings, and installation must follow the Canadian Electrical Code, provincial requirements, and inspection. For installation, consult a Licensed Electrical Contractor. Confirm the cable carries a recognized Canadian approval mark — see our CSA, cUL & ETL guide.
How to Choose
1. Indoor, concealed, dry → usually NMD90. 2. Need mechanical protection / exposed run → AC90 (BX). 3. Wet/outdoor or direct burial → neither; use the correct rated cable (e.g., TECK, underground cable). 4. Match gauge and conductor count to the circuit.
Comparison Table
| NMD90 | AC90 (BX) | |
|---|---|---|
| Jacket | Non-metallic (plastic) | Flexible metal armour |
| Typical use | Dry, concealed indoor wiring | Exposed runs / mechanical protection |
| Flexibility | Flexible | Flexible, more robust |
| Outdoor/wet | No | No (use rated cable) |
Common Mistakes
Using NMD90 where mechanical protection is required · using indoor cable outdoors/wet · wrong gauge or conductor count · assuming an online cable carries a Canadian approval mark.
Related Products
Wire & Cables · Electrical Boxes · Connectors & Fittings (Arlington)
When to Call a Licensed Electrician
For installation and for confirming the correct cable type and method for your location and code.
Frequently asked questions
Sources and Further Reading
- CSA Group product listing — https://www.csagroup.org/testing-certification/product-listing/
- Electrical Safety Authority (Ontario) — https://esasafe.com/
- Manufacturer cable datasheets — link per product
Call to Action
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