What wires needed for the basement circuits

basementelectricalwiring

I am doing the electrical work for my basement. I have a kitchen, 3 bedrooms, and 2 bathrooms. I will divide them into 4 circuits.

Circuit 1 (Kitchen):

  • Fridge
  • Freezer
  • Microwave
  • Lights
  • Blender
  • Kettle
  • Washing Machine
  • Dryer
  • etc.

Circuit 2 (Room 1 & Bathroom 1):

  • Computer
  • Lights
  • TV
  • Bathroom fan
  • Hair dryer
  • Shaving machine
  • etc.

Circuit 3 (Theater Room):

  • Computer
  • Lights
  • TV
  • Projector
  • Recliner chairs
  • Treadmill
  • etc.

Circuit 4 (Room 2 & Bathroom 2):

  • Computer
  • Lights
  • TV
  • Bathroom fan
  • Hair dryer
  • Shaving machine
  • etc.

What is the size of the wire that I have to bring to each circuit?

Should I split the Kitchen into 2 circuits (Kitchen Circuit + Laundry Circuit)?

Best Answer

Oh that it were that simple. To satisfy the National Electrical Code, if your installation is to be inspected, you need more than 4 circuits. It is complicated but a back-of-envelope calculation is as follows:

The National Electrical Code requires the following separate circuits for a dwelling unit according to 2017 NEC 210.11(C):

  • 2-20 amp circuits for the kitchen counters for small appliances. I would recommend alternating the receptacles serving the counter tops on these two circuits or split wiring them with the two circuits.

210.52(B)(1) In the kitchen, pantry, breakfast room, dining room, or similar area of a dwelling unit, the two or more 20-ampere small-appliance branch circuits required by 210.11(C)(1) shall serve all wall and floor receptacle outlets covered by 210.52(A), all countertop outlets covered by 210.52(C), and receptacle outlets for refrigeration equipment.

  • 1-20 amp circuit for the laundry with at least one receptacle.
  • 1-20 amp circuit for the garage. In the 2020 code they upped this to one for each stall in the garage.
  • 1-20 amp circuit for the bathroom(s) receptacles. Multiple bathrooms are allowed to have their receptacles on the same circuit but it is not advisable.

NEC 2020 210.11(C) Dwelling Units.

210.11(C)(3) Bathroom Branch Circuits. In addition to the number of branch circuits required by other parts of this section, one or more 120-volt, 20-ampere branch circuit shall be provided to supply bathroom(s) receptacle outlet(s) required by 210.52(D) and any countertop and similar work surface receptacle outlets. Such circuits shall have no other outlets.

Exception: Where the 20-ampere circuit supplies a single bathroom, outlets for other equipment within the same bathroom shall be permitted to be supplied in accordance with 210.23(A)(1) and (A)(2).

If your bathroom circuits are served with a separate circuit for each you can put the vent fans on those circuits. If you combine the bathrooms (again NOT advisable but acceptable) you can put the fans on the lighting circuits but if they have heaters I would advise a separate circuit depending on their current draw.

All of these circuits are required to have no other outlets. "Outlet" here doesn't just mean receptacles but any place where utilization equipment receives its power supply. e.g. a lighting outlet in the ceiling or the wall. Consequently, they need to be separate from your other circuits and the lighting cannot be on the circuit(s) with them.

In residential work, in my experience the standard is to wire the receptacle circuits with 20 amp breakers and #12 AWG wire. The lighting is normally put on separate circuits, to avoid "lights-out" if a receptacle breaker is tripped. These are wired on 15 amp breakers and #14 gauge wire. This is due to the fact that almost all lighting is now LED and draws very little current so 15 amp circuits are more than adequate for this job.

Additionally, all the receptacles in the bathroom(s) and kitchen are required to be protected by GFCI. Either on a GFCI breaker or down-fed from a GFCI receptacle first in the circuit. Almost all other receptacles are required to be AFCI protected as of the 2020 NEC.

So, in addition to the circuits required above, you would have 1 or more 15 amp circuits wired with #14 wire for the lighting for the entire basement, and 1 or more 20 amp circuits for each room you listed with the exception of the kitchen and bathrooms. Advisably two for the theater room.

The National Electrical Code requires a minimum number of circuits but you can add as many more circuits as you wish to the required minimums.

The physical wiring part of electrical work is much simpler than layout of the circuits to stay code compliant. Kitchens and bathrooms are complicated and I would advise reading the National Electrical Code carefully before finalizing your layout plan.

Sorry for the confusion on your location I don’t usually go read people’s profile and just assumed you were in the USA. I am pretty sure Canada has similar codes as the US but I am unfamiliar with the particulars. You could just use my response as reference material though.

Good Luck!

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