Friday, February 24, 2006

My Tips for DIY Electrical Wiring

I recently finished wiring my second kitchen and wanted to document and share the tips that I've learned. I'm not an electrician so when in doubt, check your local regulations and refer to the National Fire Prevention Association's National Electrical Code (NFPA 70) But, doing your wiring yourself can save you A LOT of money. It is really not that difficult if you read up on the requirements and practice with someone who has done it before. The inspectors are generally patient with you as a DIY homeowner and will help guide you along if you ask them questions.

Kitchen minimum circuit requirements:

  • Countertop outlets: Must now have two independent 20A circuits. Not required but recommended is to alternate the outlets on a counter on both circuits to keep outlets in one area from going out if one device overloads the circuit.

  • Microwave: must be on its own dedicated 20A circuit. This is an absolute must these days when most microwaves are at least 700W (mine is over 1000W) and this will often blow the circuit.

  • Dishwasher: should be on its own dedicated 20A circuit. It is not required that it be hard-wired and can be handy to put an appropriately-sized gauge plug on the dishwasher so you can just plug it into a receptacle. Best to get a flat plug since there isn't much available room behind a dishwasher for a standard plug.

  • Refrigerator: should be on its own dedicated 20A circuit, but this is not required. It is acceptable to dangle this off of one of the two countertop outlet circuits

  • Disposer: Also should be on its own dedicated 20A circuit, but not required. I prefer to use a switched receptacle for disposals so that the other receptacle is available for a hot water tap or future devices.
  • Lighting: Cannot be on the same circuit as any outlets. The thoughts are that if you blow the outlet circuit, it is safer to keep the lights on!

Other things to be aware of:

  • Receptacles:

    • Any appliance outlet in the kitchen within 6 feet of a water source must be GFCI protected.

    • Be careful not to wire outlets that should be non-GFCI downstream and in series with GFCI outlets or if an upstream GFCI trips, you will kill the remainder of the circuit leg too. If you need to put others on the same circuit, wire them in parallel or run a parallel separate power lead from the incoming feed source.

    • Some appliances with motor loads can trip GFCI circuits, such as dishwashers or refrigerators. You should likely not make those GFCI protected.

    • You're not supposed to hang anything else off of kitchen countertop outlet circuits, especially in other rooms. You can get away with this in a remodel sometimes, as I had to deal with an existing bad situation.

    • Any counter wall space of at least 12" needs to have an outlet installed on it.

    • Countertop outlets are typically placed 6" to center above the finished countertop height (which is 36" these days)

    • Receptacles: It is recommended to avoid push-in outlet terminals even where available since they are not as reliable as screw-down terminals and can cause overheating and fire in the long-run. Make sure to tighten down the screw terminals for the same reason. My 50 year-old house used the screw terminals but several wires were not tightened and the switches were quite warm because of it.

  • Switch height is typically 48" to the center of the box from the finished floor. It's best to check with existing switches in a remodel and just match that height for aesthetics.

  • Be advised that for some jobs the inspectors may require you to bring other things up to code even if they aren't part of your permitted work. For example, on my last kitchen remodel project, I had to install at least two 20A outdoor outlets, one near the front and one near the rear door since code requires this so that you aren't tempted to overload interior circuits with outdoor equipment.

  • Be careful to provide maintenance switches for appliances that are hard-wired. The circuit panel breaker does not count as a switch unless you equip it with a breaker lock to keep someone from accidentally turning it back on while you're working on the appliance/circuit

  • Outlets to bedrooms now are required to be served by AFCI (Arc Fault Circuit Interrupters). These are designed to detect arcing that can cause fires so are a safety precaution.

  • There is a bit of excessive requirements in the NEC, alot of it designed less for safety than for other things like accessibility and maintainability and ensuring licensed electricians don't do silly things like wire all of your outlets on one circuit anymore. At the same time, there are some things that the NEC lets slip that I would not, as a security professional, rely on even if you can get away with it because the design is brittle. And with safety, I'd prefer to not have a brittle protection system. One of those is that you can technically install one GFCI outlet at the beginning and chain multiple outlets downstream in series from that one and that is sufficient to meet GFCI protection. I don't know about you, but that is asking a lot of that one outlet. And GFCI circuits are not necessarily reliable forever. Why do you think they have a test button on them that you are supposed to use periodically? I prefer to use GFCI receptacles on every outlet that should be GFCI protected so that there is some failover protection. I also prefer to install a GFCI circuit breaker if all outlets on the circuit should have GFCI protection since the breaker is more reliable in general than the individual outlets. Multiple layers of protection. I got inspectors asking me why I did this but it's a bit of extra protection where it is needed most and does not cost a whole lot more.
  • Make all connections that will have wire nuts attached mechanically sound with pliers before using wire nuts. Don't rely on the wire nuts alone to hold the wires together! I've seen grounds pop out this way and leave outlets unprotected.

  • Running wires

    • Wires running through walls should be 1 1/4" back from either face of the stud for safety. Use metal nail plates to protect the wires

    • All junction boxes have to remain accessible so don't enclose them in a wall.

    • Wires need to be stapled within 8 inches of entering a box and at least every 48 inches. More staples are better.

Here's what I've just put into my kitchen as an example:

two 20A countertop outlet circuits. Refrigerator branches off of the incoming power of one of the circuits.
one 20A non-countertop outlet circuit
one 20A dedicated dishwasher circuit
one 20A Disposer circuit. Low voltage transformer and range hood (only 3A max draw) come off of that circuit.
one 15A lighting circuit for the recessed cans
one 30A electric range circuit
one 20A dedicated microwave circuit


Here are the required inspections since this is not apparent to the layperson doing this for the first time:

  1. Cover (aka Rough-in): Once you have installed all of the boxes, run all of the wire, and "tailed out" all of the grounds at least, call for this inspection. The inspectors will want to make sure you pigtailed all of the grounds before signing off. You can also pigtail any other necessary connections as well before now. You can essentially hook everything up by this point except turning on the power and connecting receptacles, switches, etc. You cannot put insulation or drywall up until this is done. If you do, they may make you rip it out to see what's beneath...

  2. Final: After everything has been completed and all of the lights and receptacles are hooked up and the power has been turned on, they will want to come back and do some tests. They will check the polarity of all of the outlets so be sure you check this first. You need to be sure to hook the black (hot) only to the brass screws! The other big thing they will check for is whether the GFCI circuits actually work. Miswiring GFCI outlets can render them worthless so be prepared for this.

Here are a couple of helpful resources: and also this checklist.


  1. Just a quick comment. Giver the nature of electronic hardware in the kitchen: ie Microwave, Diswasher & Refrig - It would be a good idea to invest in some good Surge suppression receptacles to power the equipment from.
    As more delicate equipment is installed in these devices the need to protect the is growing in acceptance everyday,
    Wel - that's my two cents worht - Good Luck

  2. (I'm a professional engineer and did electrical fire investigations for 20 years.) Given that the NFPA 70 is difficult to read and understand and also covers much more than most DIYers need, your blog is most welcome.
    I have a couple of very minor technical comments. One thing is that circuit breakers are sized to protect overheating of branch circuit wiring and are not intended to protect loads, such as a dishwasher. For safety's sake, I prefer to run 15 amp circuits rather than 20 to a dishwasher or a disposer, just because if the dishwasher fails and tries to start a fire, I don't want any more electrical power available than the minimum of 15 amps. That's plenty for normal operation of the appliance. If a light-gauge wire shorts inside the appliance, there's a better chance that a 15 amp breaker will trip. (Dishwasher doors stress a wiring harness each time the door swings. Also, leaks and condensation sometimes corrode connections which overheat, melt the pvc insulation on the wires, and cause a short, which produces even higher temperatures.)
    There's really no drawback in having several outlets downstream for a GFCI outlet. (I could go into the technical reasons, if desired.) If something trips it, there's something wrong that needs correcting.
    Your point of not running a refrigerator off of a GFCI is a good one. I've seen a couple of incidents of damaged food in a refrigerator that lost power and nobody noticed before the freezer thawed.

  3. Regarding surge protection, you can get a whole house protector for about $30 and attach it to you circuit breaker panel. They take only minutes to install.

  4. I've been meaning to get whole-house surge protection. Thanks for the tip!
    And the tip for the dishwasher also sounds like a good one.
    BTW, another tip: you have to wire GFCI outlets in parallel if you have multiple on the same circuit. They won't trip correctly otherwise. I had to rewire mine (no safety problem, but it's strange to have a different GFCI outlet trip than the one where the short occurs). It's difficult to debug.
    Also, dishwashers don't require a circuit breaker lockout if you plug them into an outlet, HOWEVER, that requires that the outlet is serviceable without removing the dishwasher. Typically, that involves running the power cord through underneath the sink cabinet.

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