13 Dec Electrically Speaking
There are several systems that operate together to make your homework. The major household systems are heating (with or without central air conditioning), plumbing and the electrical service. Each system has its own possible problems and dangers when you use it or work on it, so be aware of the safety. But, I believe that the electrical system has the potential of being the most dangerous, especially in older homes with services that have not been upgraded in recent years.
Finding the Limits of Your Electrical Services
The first thing you want to check is the limitations of your current services. The quickest and easiest checkpoint is your service panel, also called the fuse or breaker box. If your panel has breakers (they look like light switches laying on their side), chances are good that you have at least 100-amp service coming into your home. You can verify this by adding the amp values of each breaker in the panel.
If your home was built in the 1950s or earlier, you may only have 60-amp service or possibly even 30-amp service. If your service panel has round, screw-in fuses, they will likely be 15 amps each. Two fuses, 30-amp service. Four fuses, 60-amp service. These service panels are very easily overloaded and can cause a fire if you are not careful. Check with your power company to see if your house is being supplied with at least 100-amp service. If not, ask about getting it upgraded. You should also upgrade your service panel to at least 100 amps as soon as you can. This can be a DIY project if you are comfortable working around electricity. Otherwise, an electrical contractor should be called in to switch out the service panels.
If your home was built before World War II, you may have knob-and-tube wiring. This type or wiring gets its name from the ceramic knobs that hold the wires and the ceramic tubes that let the wires pass through walls and ceilings. These wires are wrapped in rubberized cloth for this type of wiring. If you find it, it should be replaced as soon as possible, because of its potential as a fire hazard.
Once you have checked the service panel and know what your service is (30, 60, or 100 amps), you need to map out the circuits. Each breaker or fuse is one circuit and should supply no more than its amp rating. Some clues that indicate you are overloading a circuit include fuses that are always blowing out or breakers that always get tripped, and lights that dim or flicker with another light is turned on, or when an appliance turns on. If you are blowing fuses, don’t be tempted to replace a fuse with a larger one. This can lead to the wires themselves becoming overloaded, heating up, and causing a fire. If you have replaced a fuse with a larger one, you should put in the correct size fuse as soon as possible and then look for reasons why the fuse is being overloaded. If your lights dim or flicker, you are coming close to the maximum load on that circuit and you need to reduce the load. But, how can you know what circuit handles which area and how can you tell if it is overloaded?
Mapping Your Household Circuits
Start by checking the inside door of your service panel. If you see a listing of which area, or branch, the fuse or breaker controls, you’re halfway there. All you need to do is check that it’s correct. If you don’t see one, you will need to make one up yourself.
Start by drawing a floor plan of your home, marking the location of each outlet, light fixture, switch, and appliance. Next, you will check what goes off when you remove a fuse or flip off a breaker. This is where a helper comes in handy, and is a perfect opportunity to involve your spouse or kids in the project. Turn on all the lights in the house, then turn off a breaker or remove a fuse and have your helper check which lights have gone off. Your helper then marks these lights and outlets with the number of the circuit on the corresponding outlet or switch on your floor plan.
If there are any outlets that do not have anything plugged into them, have your helper plug a radio or lamp in each outlet to see if it is live. Check all unused outlets in the house with each fuse or circuit you test. In many older homes, circuits can run all over the house. Bigger appliances, such as microwave ovens, dishwashers, and even garbage disposals often have their own circuit. If you test a breaker or fuse, check to see if an appliance is off.
After you have tested all the fuses or breakers, go through the house with your circuit map and check to see if there are any outlets, switches, lights, appliances or other electrical devices that were either left off the map from the start or were passed over during the testing.
If you are working on this by yourself, plug in a radio with the sound turned up loud enough for you to hear from your service panel. Flip breakers or remove fuses until you hear the radio stop playing. Once it goes quiet, you have found the circuit for the general area and you can then go to the area and begin testing and mapping.
Wires and Cable
If you are planning to rewire your home, or supplement your existing wiring, it is important that you use the right type and size wire for the job. The wrong type of wire may allow water to enter the wiring, while the wrong size wire may overheat, both of which could cause a fire.
The terms wire and cable, while often substituted for each other, are not the same thing. Wire is the individual conductor, wrapped in its own insulation. Wire comes either solid or stranded. Cable, on the other hand, is a collection of wires, each with its own insulation, and wrapped in a plastic or metal sheath.
Types of Wire and Cable
- Type T wiring is used for general, indoor electrical service. The insulation is thermoplastic and provides protection under a wide temperature difference.
- Type TW wiring has a heavier insulation and is used outdoors and in damp places such as crawl spaces and basements. This wire should not be directly buried underground.
- Type THW wiring is much like Type TW wire but is more heat resistant.
- NM Cable is the type most often used in homes. It contains two or more Type T wires and a bare copper grounding wire. These are wrapped in paper with a plastic covering over everything. NM Cable cannot be used where there is any chance of moisture.
- NMC Cable is similar to NM Cable but is for use in damp areas. The wires are embedded in a solid plastic coating to keep out moisture.
- UF Cable is also moisture resistant and is for underground use, such as from your house to your garage.
- Armored Cable has a heavy paper wrapping and a metal wrapped metal coating. It is used in areas which are exposed to possible wear and tear.
Wire Size and Use
When it comes to wire size, the greater the number, the smaller the wire. Number 16 wire is also known as bell wire and is used in doorbell circuits. Most home wiring is either Number 14 or number 12. Number 14 wire will handle 15 amp service, while number 12 will handle 20 amps. Most outlets and switches are rated for 15 amps, which means that most of the wiring in your home should be number 14.
However, according to the National Electric Code, number 12 wire can be used with 15 amp rated outlets and switches. If number 14 wire is used with an outlet or switch rated for 20 amps, there will be too much electricity going through the wire and it will overheat and possibly cause a fire.
So, when you re-wire, make sure you pay attention to the type and size of your wire.
Always remember that you need to be careful when working around electricity. Only remove cover plates on outlets and switches when it’s necessary and replace them as soon as you are finished. This goes for the cover plate on your service panel.
Always keep the door to the service panel closed when you are not working on, or inspecting, the panel. And if you have to remove the cover panel to work on the inside of the service panel, remember that there will be power entering the box (and therefore live wires), even if you pull the main fuse or flip off the main breaker.
Many jobs that involve electricity can be done by the home handyman, but there is nothing wrong with asking for help if you think you may get in over your head. Safety is the most important thing to remember when working with electricity.