What you're looking at is a special type of wiring known as Fixture Wire. Fixture wires are conductors used for wiring fixtures and control circuits, they are not branch circuit conductors. There are special requirements and uses for fixture wires, which are covered in article 402 of the National Electrical Code (NEC). Article 240.5(B)(2) also addresses fixture wires.
240.5 Protection of Flexible Cords, Flexible Cables, and Fixture Wires. (B) Branch-Circuit Overcurrent Device. (2) Fixture Wire.
Fixture wire shall be permitted to be tapped to the branch-circuit
conductor of a branch circuit in accordance with the following:
(1) 20-ampere circuits — 18 AWG, up to 15 m (50 ft) of run length
(2) 20-ampere circuits — 16 AWG, up to 30 m (100 ft) of run length
(3) 20-ampere circuits — 14 AWG and larger
(4) 30-ampere circuits — 14 AWG and larger
(5) 40-ampere circuits — 12 AWG and larger
(6) 50-ampere circuits — 12 AWG and larger
In cooktop installations where fixture wires are used, you may see #8 or #6 wire from a dedicated breaker to a junction box behind the fixture. You'll then see #12 or #10 wire from the junction box to the cooktop. Because of articles 402 and 240.5(B)(2), this is a valid installation technique.
Mean of Disconnect
When dealing with permanently connected appliances, you'll want to check article 422 of the NEC. Article 422.31(A) tells us if the appliance is rated less than 300 Volt-Amperes or 1/8 Horsepower, the branch-circuit overcurrent device can be the disconnecting means. If the appliance is rated over 300 Volt-Ampheres or 1/8 Horsepower, the circuit breaker can be the disconnect if:
- The circuit breaker is within sight from the appliance.
- Or the circuit breaker is capable of being locked in the open position.
422.31 Disconnection of Permanently Connected Appliances.
(A) Rated at Not over 300 Volt-Amperes or 1⁄8 Horsepower. For permanently connected appliances rated at not over 300 volt-amperes or
1⁄8 hp, the branch-circuit overcurrent device shall be permitted to
serve as the disconnecting means.
(B) Appliances Rated over 300 Volt-Amperes or 1⁄8 Horsepower. For permanently connected appliances rated over 300 volt-amperes or 1⁄8
hp, the branch-circuit switch or circuit breaker shall be permitted to
serve as the disconnecting means where the switch or circuit breaker
is within sight from the appliance or is capable of being locked in
the open position. The provision for locking or adding a lock to the
disconnecting means shall be installed on or at the switch or circuit
breaker used as the disconnecting means and shall remain in place with
or without the lock installed.
- When installing devices like cooktops, always follow the manufacturers installations instructions.
- If you are unfamiliar with proper wiring methods, please contact a qualified Electrician (which will also be stated in the manufacturers installation instructions).