Indoor Electrical Safety Check Circuit Map and Power Audit

Circuit Map and Power Audit

While you cannot perform your own electrical inspection unless you're a qualified, licensed electrician or electrical inspector, something you can do is create a detailed circuit map and perform a power audit. This is not a substitute for an electrical inspection, but it will help you establish and maintain a safer electrical system.

A good circuit map goes beyond what the sticker on the inside of the electrical panel door provides. It details every receptacle and fixture each circuit serves. To create one is a simple, though admittedly time-consuming process of shutting off a single circuit at a time and determining which outlets and lighting fixtures have been affected each time.

As you proceed, note what appliances are plugged in at each receptacle. circuits can only handle a specified total wattage of all the electrical products connected to that circuit. If too much wattage is demanded from a circuit, serious electrical problems can result. Here is an easy equation to use to determine what a circuit can handle:

Volts x Amps = Watts

Your electrical panel will indicate your system's voltage, and each fuse or circuit breaker is marked for its amperage. Using the equation above, a 15-amp circuit in a 120-volt system can carry a total of 1800 watts. It is not recommended that you exceed 80% of the total circuit capacity at any given time, in this case 1,440 watts.

Now, find the nameplate on each appliance indicating its power rating in watts. Note the appliance and its power rating on the entry for that circuit. Lamps and light fixtures, too, should note the maximum wattage they can take. If you cannot find the power rating, contact the manufacturer.

Finally, do the math. Add up the power demand of every appliance and fixture drawing power from the circuit. A typical entry in the circuit map should look like this:

circuit #3- Kitchen-20 amps
Total allowable capacity (80% of total capacity) = 1920 watts
Serves three receptacles along the north and west walls of the kitchen, the kitchen ceiling lighting fixture (120 watts), and light fixture over the sink (60 watts). Appliances plugged into receptacles include the coffee maker (800 watts), toaster (800 watts), radio (30 watts), phone/answering machine (100 watts).
Total demand on circuit = 1,910 watts.

If your total exceeds what the circuit is designed to provide, you may have a dangerous overload and should take immediate measures to alleviate the demands on that circuit by moving some appliances to another less taxed circuit, or by adding another circuit. In fact, you may find the total demand on your entire system exceeds the service to your home. In that case, consider contracting with your utility for a "heavy up", or upgrade to a higher level of electrical service.

A good circuit map will let you know at a glance, which circuits are overloaded and which are still available for additional use. Also, in the event of an electric shock or electrical fire, or if you need to remove power to do home maintenance or repairs on or around a circuit, you'll know without a doubt which circuit to shut off.