Distinguishing a Lumen from Illuminance

Light output is measured in lumens. According to The American Heritage Dictionary of Science, a lumen is a unit of luminous flux equal to the amount of light from a source of one candela radiating equally in all directions. A candela is a unit of luminous intensity equal to 1/60 of the radiating power of one square centimeter of a black body at 1,772°C. You can draw two conclusions from this information:

• The higher the lumen measurement, the more light you’ll have to work with from a fixture.
• Authors can easily get carried away when they have too many reference books at their disposal.

Illuminance, which is measured in foot-candles, is the amount of light hitting a point on a surface. A foot-candle is (easily enough) defined as the amount of light produced by one candle on a surface one foot away. We can’t see illuminance, but we do see luminance or brightness, although this is somewhat subjective. (What appears to be dim light to me might be plenty bright to you.) Architects and lighting consultants take all these measurements into consideration when they calculate the lighting needs of buildings.
Comfortable lighting selections and light levels are determined by the tasks that require the lighting, the distance between the light and the task, and the degree of glare. One definition of glare is excessive contrast between the intensity of light on a particular object or surface and the surrounding area or background; indirect glare is the glare produced from a reflective surface. Too much contrast between them causes glare. (Computer screens are a common example.) You can reduce this glare by …

• Installing fixtures that keep the light level appropriate for the task at hand.
• Using a louver or a lens to block or redirect the light.
• Carefully considering the placement and spacing of light fixtures.

Another measurement of lighting quality is how well it enables you to see colors accurately. The better the color rendering, the more pleasing the living space. Color-rendering capability is based, naturally enough, on the color-rendering index (CRI), which measures from 1 to 100. (Natural daylight measures at 100.) The higher the rating on the CRI, the more lifelike and accurate the object being viewed.

Measuring Your Lighting Needs

The NEC calls for a minimum calculation for general lighting and receptacle loads of three watts per square foot of living space. This comes out to approximately one circuit every 575 square feet. That doesn’t amount to a lot, but remember, electrical codes only establish minimum standards. In reality, you’ll want lighting everywhere.
Consider the different areas of your house and their individual needs:

• Kitchen. Overhead lighting, natural light from windows and sliding doors, work light over counters, a light over the stove.
• Bathrooms. Primarily lights over the sink(s) and lights over the bathtub and toilet, depending on the size of the room.
• Dining room. A hanging light over the table, recessed ceiling lights, or possibly wall sconces. This room often has a dimmer switch to tone down the light.
• Bedrooms. Children’s rooms often get ceiling lights. Master bedrooms might depend more on reading lamps and switch-controlled receptacles, although large rooms can use recessed ceiling lighting as well.
• Hallway. You might want a long track light to highlight artwork on the walls.
• Garage. At least one light per bay over the hood of the cars. It’s even better to add one or two at the other end so the trunks are illuminated.
• Basement. Depends on whether the space is finished or unfinished. In either case, you want at least enough ceiling light to cover the entire area thoroughly, leaving no dark spots.
• Closets, storage rooms. At least one ceiling light.
• Outdoors. At a minimum, one light over each entry door and over the garage doors. It’s even better to consider lights to line walkways and illuminate gardens or security lighting for back and side yards.

Your use of a room obviously will determine your choice of lighting fixtures, their locations, and their number. A single fluorescent ceiling light will fulfill all the working requirements of most closets because the requirements are pretty basic: to shed enough light for you to identify and choose your clothes. A kitchen, on the other hand, requires all kinds of light for a modern homeowner. You need lights over counters for close work so you can chop, dice, and mince vegetables instead of your fingers. Overhead lights enable you to read the newspaper and get a better look at what’s hiding in the back of your pantry. A dimmer-controlled hanging light over the eating area lets you tone things down for a late-night meal. Anywhere you’ve got a wall, ceiling, or floor, you can install a light. It’s simply a matter of extending a circuit or running a new one and choosing your fixtures. The science of lighting is a little more complicated.

How Illuminating my home is.......

We are way beyond the point when lighting was simply functional, allowing us to work and not stumble around after the sun went down. If function was all it meant to us, every room in our house would have one huge, efficient, fluorescent light fixture on the ceiling and maybe a night-light or two for after dark. Instead, lighting does much more such as …

• Create a mood or atmosphere.
• Define a space.
• Provide security and safety.
• Highlight artwork or a section of your home.

Your lighting needs will be defined by these factors and others. Before you install a particular type of lighting, ask yourself the following questions:

• Who will be using this area and for what purpose?
• Do I want a traditional or modern look?
• How often will anyone be in this room?
• How much am I willing to spend?
• Is energy conservation important to me?

At a minimum, the code calls for one switch-controlled light per habitable room. Hallways, stairways, and garages also must meet this code requirement. This can be accomplished with permanent fixtures, such as ceiling lights, or through a switch-controlled receptacle into which a lamp can be plugged. Bathrooms and kitchens, however, must have an installed fixture. Your first step is to establish your minimum lighting needs and then choose the style of fixture you want to meet them.

Grounding an Old Receptacle

A properly grounded system ties each device, appliance, and fixture back to the service panel with a separate grounding conductor (the bare copper or green insulated copper wire). It’s unrealistic to attempt this with an old electrical system unless you’re replacing it (in which case, the grounding would be part of replacing the system). You also could install a GFCI in place of an existing, two-wire receptacle. The National Electrical Code allows an ungrounded, two-wire receptacle to be replaced with a GFCI. A GFCI can even protect any receptacles downstream (away from the panel or power source). A GFCI used in this manner will only protect you from ground faults; it will not act as a ground for any equipment plugged into the receptacle(s). As a rule, it’s best for GFCIs to protect only a single box, not multiple receptacles. If you try to use one GFCI to cover multiple receptacles, you might experience nuisance tripping due to the greater sensitivity to current fluctuations. A GFCI installed to replace a twowire receptacle should be marked “No Equipment Ground.” A GFCI must be wired according to stamped terminals on the back of the receptacle. They will be marked “Load” and “Line” as well as “Hot” and “White.” The hot wire (which runs from the panel or fuse box) is the line conductor; anything going off to another load or receptacle is the load conductor. How do you know which is which? You’ll need your voltage tester.
With the power off and the old receptacle removed, separate all the wires in the box so they’re not in contact with each other (or with the box if it’s metal). Turn the power back on, and put one end of your probe on one hot wire and one on the neutral that is paired with the hot you are testing. If the bulb doesn’t light up, try the other black wire and neutral. The one that lights up the tester’s bulb is the line conductor. It’s the one receiving power from the current you switched back on at the service panel or fuse box. Connect this to the “Line,” “Hot” side of the GFCI. It is very important that the line side hot and neutral conductors or wires be connected to the “Line” side of the GFCI; otherwise, the GFCI will trip or will not work at all. If the line and loads are reversed, the GFCI will still have power if it is tripped, producing a hazardous situation.
As an alternative to installing a GFCI to replace an ungrounded receptacle, it is permissible to install a grounding conductor to an ungrounded circuit by using an individual No.12 insulated green copper conductor to connect each receptacle being grounded to the closest cold-water pipe. The grounding conductor will then have to be secured to the pipe using an approved clamping device. It also can be run directly back to the panel and installed in the grounding/ neutral bar.

Installing a New Receptacle

Receptacles are a little more straightforward than three- and four-way switches. With a single duplex receptacle, you’re dealing with one or two cables coming into the box. An end-of-the-run receptacle will have one cable, and a middle-of-the-run will have two. The receptacle has two sets of terminal screws, silver for the neutral wires and brass for the hot.
After shutting off the power and testing the terminal screws, remove the outlet by loosening the screws attaching it to the box. Remove the hot and neutral wires, noting their position on the outlet (hot upper, hot lower, neutral upper, neutral lower) by marking the position on an attached piece of masking tape. Reconnect to the new receptacle in the same locations, and gently push the wires back into the box while reattaching the new receptacle. Turn on the power at the service panel or fuse box and test.

Two-Wire Grounding

Do the following to test a two-slot receptacle: Place one probe in the hot slot and the other end on the screw securing the cover plate. The screw must be clean as well as paint and grease free.

• If the receptacle is grounded, the tester’s bulb will light up.
• Put the probe in the neutral slot if the tester does not light up in the hot slot. If it lights, the receptacle is grounded, but the neutral and hot wires have been reversed and are attached to the wrong terminals. If the bulb doesn’t glow at all, the receptacle isn’t grounded.
• To be absolutely sure that the receptacle is grounded (if your test indicates that it is), turn the power off and remove the cover plate. Check to see if an actual grounding conductor is present.

Test for Grounding

You can test a grounded, three-slot receptacle for grounding (remember, the power is on) by placing one probe of your tester in the short slot and one in the hole for a plug’s grounding pin. The short slot is for the hot wire. The bulb should glow to indicate that the receptacle is grounded. If it doesn’t, keep one probe in the grounding hole and place the other one in the longer, neutral slot. In this position, if the bulb glows, it shows that the receptacle is grounded, but the black and white wires have been reversed (they’re attached to the wrong terminal screws) and should be corrected. If the bulb doesn’t glow in either case, the receptacle isn’t grounded. A three-slot receptacle that isn’t grounded is misleading and dangerous to a user. It might indicate that only the individual receptacle is incorrectly wired or that it was inadvertently used to replace an ungrounded receptacle. Either way, you want to know so you can correct the problem.