Nonmetallic sheathed cable (NM or Romex-style) is the branch wiring most Chicago homes use indoors. After about 2001, manufacturers began color-coding the outer jacket so electricians and inspectors can spot wire gauge at a glance. Older runs often still have white jackets only, so you must read the print on the sheath. For how gauge ties to breaker size, start with our right wire gauge guide.
Why Jacket Color Matters
The outer vinyl jacket color points to the AWG size of the insulated conductors inside. Matching wire size to breaker rating is what keeps conductors from overheating under load. Using a jacket color as a quick visual check reduces install mistakes, especially when rewiring kitchens, laundry rooms, and DIY panel work goes wrong.
Color coding is widely used but treat printed markings as the source of truth. If the jacket says 12 AWG and the breaker is 20A, you have a consistent starting assumption. If print is worn, faded, or missing, do not guess from color alone.
Common NM Jacket Colors in Homes
White usually marks 14 AWG cable for 15-amp lighting and general receptacle circuits on many older plans. New work often still uses white 14-2 for lights where code and load allow.
Yellow usually marks 12 AWG for 20-amp circuits: kitchen counter receptacles, bathrooms, laundry receptacles, and many dedicated small appliances. Remodeled Chicago kitchens lean heavily on yellow 12 AWG.
Orange usually marks 10 AWG for 30-amp loads such as some water heaters, dryers (depending on the circuit), and larger dedicated equipment. Confirm the appliance nameplate before buying cable.
Black can mark either 8 AWG or 6 AWG, which is why black jackets need extra care. 8 AWG is often associated with 40/45-amp class circuits; 6 AWG is often used for 50/55/60-amp class feeds depending on terminals and listing. Always read the gauge printed on the jacket.
Gray jackets are commonly used for underground feeder (UF) style cable rated for burial and wet locations. That is not the same product as indoor NM-B. Do not use indoor NM outdoors or buried.
Jacket Print and Conductor Count
Markings such as 12-2 WG mean two insulated 12 AWG conductors (black hot, white neutral) plus a bare or green ground. 12-3 WG adds a red conductor for three-wire circuits: multiwire branch circuits, two switch legs to a light, or some dryer and range setups when allowed.
The printed count never includes the ground as an “extra insulated” wire for load. Grounds are for fault current and bonding. Never use the bare ground as a neutral or hot.
Conductor Insulation Colors Inside the Cable
Inside the jacket, white insulation is typically the grounded neutral, black is a hot, and red is a second hot when present. Green or bare copper is equipment grounding. In switch loops and some older installs, white can be re-identified as a hot with tape. Never assume a white wire is always a neutral without checking the device.
Chicago Remodel Notes
Basement unfinished runs, attic punch-ups, and aluminum-era buildings often mix cable eras. White jackets on old NM may be 12 or 14; you must read old print or measure carefully. Adding a 20A kitchen outlet circuit usually means yellow 12 AWG NM-B, not reusing thin 14 AWG from a lighting run.
Overload heat and bad junctions still cause fires even when cable color looks right. Pair cable selection with panel capacity checks and our electrical fire prevention practices.
DIY Limits
You can read jacket colors to understand existing circuits, photograph labels before opening walls, and plan which rooms need 15A vs 20A. Stop at new home runs, panel landings, multiwire neutrals, and any work that needs a permit. Undersized wire under a oversized breaker is a classic fire setup.
If breakers trip after a remodel, receptacles warm up, or you find mixed gauges on one circuit, call for an inspection. Our licensed residential electrician team installs and corrects NM branch circuits across Chicago and nearby suburbs.
Need Help Matching Cable to Breakers?
STS Electric rates existing wiring, replaces damaged NM, and installs new kitchen, laundry, and subpanel feeds with listed materials. Call (773) 721-1111 before buying cable for a DIY project if you are unsure which jacket and gauge belong on your breaker.
