The Circuit Detective    -  Various Device Issues

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Understand Light Bulbs,
Ungrounded or Switched Outlets, etc.


For problems with most other wiring, circuits, and connections, be sure to see my Main pages. This page is about some specific electrical items whose features have implications for troubleshooting them or their circuits. Two similar pages address specific Appliances and Controls (automatic switching devices).

2-hole receptacles
Doorbells
Light bulbs
Receptacles
Smoke alarms
Switched outlets

2-hole receptacles. Electrical boxes were commonly provided with grounding wires only beginning in the mid-1960s. But over the years, many homes built before then have been given ground-type receptacles (3-holes) in order to physically accommodate 3-prong cords. Unless new cables or ground wires were run to these outlets, however, these receptacles are lying, seeming to promise grounding when there is none. And the simple 3-hole outlet tester used by home inspectors at the time of a home being sold will reveal this. Such outlets must either revert to having 2-slot receptacles (still available and legal for that situation) or be given grounding (a wire back to the panel from each circuit being grounded) or be protected by a ground-fault interrupter (though this won't help surge protector strips do their job).

Two-prong to 3-prong adapters (commonly gray) usually do nothing more than allow you to plug a 3-prong cord in; they still lie about the grounding. The exception is if the metal box was grounded even though the installed receptacle was one with only two slots. This was done briefly in the early 1960s or so. The way to tell if such a box is grounded is if it will run a light bulb (in a socket with wires) from the hot slot to the box.

Doorbells. The most common doorbell system in homes runs on 12-16 volts and consists of a pushbutton, a transformer, and the chime itself. These are wired in relation to one another with 18-22 gauge bellwire, thermostat wire, or phone wire; only two wires are usually needed between these components. In the 1940s through 1960s it was common for the chime to be able to ring differently for front and back doors, and so two pushbuttons were wired. More recently electronic chimes have become available; they may need a stronger transformer and/or more wires. Among the problems that can develop are a sticky chime-plunger or pushbutton, a burned out transformer, and of course loose wires.

Light bulbs. Since they are so basic to us, light bulbs can also be a headache. They burn out, they come in too great a variety, and they can even damage some kinds of switches.

Light fixtures with standard sockets will accept a standard pear-shaped bulb of almost any wattage, but most fixtures are only designed to handle the heat of 60-watt bulbs or less. Anyone unaware of this is likely to replace burned out bulbs with hotter ones, either accidentally or in order to get more light. This will tend to slowly cook the fixture and the nearby ceiling -- not a good idea. Running a bulb with too high a wattage can also make a recessed light turn itself off and later back on. This is from a built-in feature meant to prevent exactly the cooking I mention.

The wattage of bulbs also needs to be limited when they are to be controlled by dimmers or motion sensors. The common limits for these are 600 watts and 300 watts respectively (total watts of all bulbs being controlled) . Any dimmer switch will always produce some noticeable heat in itself when operating, but a dimmer running too many watts will be extremely hot.

There are a variety of reasons that bulbs will burn out too soon. When the fixtures containing them cannot dissipate their heat (as mentioned above), it takes a toll on the bulbs. If the lights are ones that are left on a lot -- like outdoor lights left on all night -- then the bulbs may be living their full life but will simply have to be changed more often than others. But other things can contribute to early failure. Bulbs may be of cheap quality. Or there may be loose, arcing connections in the socket or in the wiring of the circuit. See my Light bulb article.

The life expectancy of a bulb will also be affected by the quality of power from the power company. This includes the little surges and spikes that are better known for their effect on computers. But it also includes the basic voltage level coming to the home from the utility. Many homes receive more than the average 120 volts that most bulbs are designed to handle, and this shortens their stated life. A good solution to this is to look for the same bulb but with a "130v" rating stamped on the bulb instead of "120v". The light output of these wonít be quite as bright, but you will spend less of your time getting the ladder or stool out again.

Besides these incandescent bulbs, fluorescent bulbs and tubes are common. Replacing the straight fluorescent tubes can be tricky. If they donít twist into place right, they wonít work right. On the other hand, twisting too forcefully can break an end socket. If the fixture has two or more tubes and isnít working very well, it is best to replace them all with brand new ones (from the store is more reliable than from the shelf). The tubes work in pairs, so that if one of the two tubes is bad, neither will work well. This is one reason it is simpler to get all new. The other reason is that tubes will tend to die around the same time as each other anyway.

Compact fluorescent bulbs that screw into a standard socket are good energy-savers. (Or are they? See my Article on efficient incandescents.) However, they have a limitation that is not well known. Most dimmer switches and most electronic timers are not designed to work with these bulbs. These special switches will meet or dish out an early death if they try. Video.

One phenomenon that can occur with compact fluorescents is this. Though turned off, if these bulbs are controlled by a LIGHTED switch, a small pulse of light may be visible every minute or so, especially in a dark room. This is due to how the lighted switch needs to run a little current through the bulbs.

Visit this site for More on light bulbs.

Receptacles. ="Plug-in" ="Outlet". A homeís "plug-in" outlets are termed "receptacles". They do a lot of slave labor for us, so that we take them for granted -- until they give us trouble, like many electrical items.

It helps to distinguish localized trouble from system trouble. If a receptacle, or even a few in different parts of the home, have occasional trouble running things, and this is affected by manipulating the cord-end as it is plugged in or out, the receptacle is probably worn out. By this I mean that the receptacleís springy receivers, which hold on to the prongs of the cord being plugged in, are bent or "sprung" from multiple use or abuse. This is very common at receptacles that are out in the open in a room or hall, that is, where the vacuum cleaner is often used. When the vacuum cord is stretched to its limit, it will be pulling (sideways) on the receivers, bending them. To bend a cordís own prongs to match is a poor stop-gap solution. Such receptacles need replacement.

On the other hand, if the outage is solid, long-lasting, and affects other outlets in the same area, it has something to do with the electrical system. The simplest possibilities include a tripped breaker or ground-fault interrupter (GFCI). Resetting a GFCI involves pushing its reset button in. (Finding the right GFCI is another matter). A tripped circuit breaker is reset by first turning it very firmly off, then on. If it wants to retrip quickly, a short circuit is happening. I will mention one origin of short circuits because it has to do with receptacles. If the screw that holds the coverplate to a receptacle is longer than usual, it can break the receptacle apart internally and set up a short.

Beyond these, a system outage will be from a poor connection somewhere along the circuit. The problemís location will occasionally show itself as a browning or discoloration visible on the face of the receptacle or its cover -- signs of heat damage. If not, see Outage. If heat itself is felt at a receptacle, this can also be a sign that a connection is in trouble and about to give up. However, heat and browning will sometimes have to do with a particular heavy load -- a space heater, for instance -- that has been used at the particular receptacle. That would fall back in the "localized trouble" category. In either case, that receptacle would need to be replaced and its wire connections improved.

Smoke alarms. If a smoke alarm is "direct wired" (whether it has a battery as backup in addition or not), it will often also be interconnected with other smoke alarms in the home by means of a third insulated wire (usually red in the house-wiring and yellow or orange from the alarm); the black and white wires of the alarm are to attach to black and white wires of the home's electrical system. When there is such interconnection, it can be hard to determine which alarm is setting all of them off, and one alarm may not be replaceable except with an alarm of the exact same brand and model; so replacing all at once may be necessary. When alarms include batteries, they may sound a signal of some sort to warn you that the battery is low.

Switched outlets. By code most rooms must have a light, which is to be controlled by a wall-switch. Since home designers may want the appearance and placement of lights to be versatile, plug-in receptacles for portable lamps in living, family, and bed rooms etc. are allowed to be what is switched, rather than a permanent fixture. See my Switched outlet article.

In the 1950s and 1960s an entire outlet or two in these rooms might be switched. Since then it has been more common to switch just the top or bottom half of our usual "duplex" receptacles. This has been made possible by the fact that the top and bottom halves of modern receptacles are electrically connected by two accessible and removable metal tabs to the right and left of the center of an upright-mounted receptacle. See examples in my Tour of a Circuit or Connections tutorial.

For only half of such a receptacle to be switched, the tab on the hot (black or red) side must be broken off by bending it back and forth several times. The wire that is made hot by the switch is connected at the receptacle to a hot-side terminal on the top (or bottom) half, with wires that are to be always hot connected on the other half. The neutral (white) wires are all connected anywhere on the "white" side of the receptacle, and the tab on that side is left in place. Any wire (usually red) that is supposed to go on to another receptacle in the room to switch half of it as well, needs to connect to the hot side on the same half as the one made hot by the switch.

If receptacles have recently been replaced in a room, and the switch for the room no longer turns any receptacle off, then hot-side tabs have probably not been removed from those new receptacles that were replacing old ones which had been switched. The presence of a red (switching) wire attached to a new receptacle will tend to mean it had been switched before. If all the hot-side tabs at such places in the room are not broken off, the switch will not be able to turn lamps off anymore at any of those spots.


"I am the farthest thing from a DIYer that has ever lived. I had an electrical problem in my home and found your very well done website which guided me through a simple fixit." -Mark, CA

© 2005-2013 Larry Dimock

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