Lighting
Lighting installation
Swapping one fixture for another on an existing box is quick. Putting light where there is none means a new box, a cable route and a switch, and that is where most of the work lies.
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Common lighting jobs and what each needs
| Job | What is involved | Watch for |
|---|---|---|
| Replace a fixture | Disconnect, check the box and wiring, mount and connect the new fixture | Heavy fixtures need a box rated for the weight; brittle old insulation in the ceiling box |
| Recessed (can or wafer) lights | Cut openings, run cable between lights, connect to a switch | Housings must be IC-rated where they touch insulation; joist positions limit the layout |
| Under-cabinet lighting | Low-voltage or line-voltage strips with a concealed feed | Where the driver or transformer will live, and how it is switched |
| Outdoor and security lights | Weatherproof boxes, wet-rated fixtures, often a new switch or sensor | GFCI protection where outlets are added; cable burial depth for post lights |
| A light where none exists | New ceiling box, cable to a new or existing switch | Route through the attic or ceiling; patching if there is a floor above |
Boxes, ratings and heat
Every fixture hangs from an electrical box, and the box has a weight limit. A standard ceiling box supports a typical fixture of up to 50 pounds. Heavier chandeliers need independent support from the framing.
Fixtures are also rated for where they go. A damp-rated fixture suits a covered porch or a bathroom ceiling; a wet-rated one is needed where rain or spray can reach it. Recessed lights in an insulated ceiling must be rated for insulation contact, or the insulation has to be kept clear of them.
In older houses the ceiling box is where insulation suffers most, because decades of hot bulbs have baked the wire. If the conductors crumble when the old fixture comes down, the repair is done before the new one goes up. See house rewiring for what that can lead to.
Switching and dimming
- LED-rated dimmers
- Old dimmers were built for incandescent loads. On LEDs they cause flicker, buzzing and lamps that will not turn fully off.
- Minimum load
- A dimmer driving one or two small LED lamps may be below its minimum load. The fix is a dimmer designed for low loads.
- Three-way control
- A light switched from two places needs a traveler cable between the switches, or a listed wireless companion switch.
- Occupancy and daylight sensors
- Useful in garages, closets and outdoors. Some energy codes require them in new work.
- Neutral at the switch
- Smart switches and many sensors need one. Recent codes require it in new switch boxes; older houses may not have it.
How a recessed lighting job is planned
Decide what the light is for
General light, task light over a counter, or accent light on a wall. Each uses different spacing and beam angles.
Find the joists
Layout is adjusted to the framing, ducts and pipes above the ceiling.
Check the circuit
LED lights draw little, so an existing lighting circuit usually has room. The electrician confirms it.
Cut, wire and fit
Openings are cut, cable is fished between them and the lights are connected and sealed to the ceiling.
Set the dimming
The dimmer is matched to the fixtures and its low-end trim adjusted so the lights dim smoothly.
What changes the scope of a lighting job
- Access above the ceiling
- An open attic makes new lighting far quicker than a ceiling with a finished floor above it.
- Ceiling height
- High and vaulted ceilings need staging or a lift.
- Ceiling material
- Plaster and lath, and concrete, are slower to cut than drywall.
- Number of switch locations
- Each additional control point adds cable and a box.
- Permit
- Replacing a fixture rarely needs one. New lighting circuits and outdoor wiring commonly do.
Lighting terms explained
- Lumens
- The amount of light a lamp gives. Watts measure the power it uses, not its brightness.
- Color temperature
- Measured in kelvin. About 2700 K is warm white and 4000 K is a cooler, neutral white.
- IC-rated
- A recessed housing approved for direct contact with insulation.
- Driver
- The electronics that power an LED fixture. A failed driver is the usual reason an LED fixture stops working.
What to decide before a lighting quote
What each room is used for
Task lighting, general lighting and accent lighting are laid out differently.
Fixtures
Who is supplying them, and their weight and rating.
How you want to control them
Switch locations, dimming, sensors or smart controls.
Access
Whether there is an attic above the ceiling.
Lighting installation questions
Can any fixture go on any ceiling box?
No. The box must be rated for the fixture's weight, and ceiling fans need a fan-rated box. See ceiling fan installation.
Why do my new LED lights flicker?
Most often an incompatible dimmer. If they flicker with no dimmer, see flickering lights.
Can lights be added without damaging the ceiling?
With attic access, usually yes apart from the openings for the lights. Without it, expect a few small access holes to patch.
How many recessed lights does a room need?
It depends on ceiling height, the light output of each fixture and what the room is used for. A layout is planned around the joists and the tasks, not a fixed count per square foot.
Can I replace a light fixture myself?
Where local rules allow, a like-for-like swap on a sound box is manageable with the breaker off and the circuit tested dead. Stop if the wire insulation is brittle or the box is loose.
Do outdoor lights need a special circuit?
Not always. They can often extend an existing circuit, with wet-rated fixtures and boxes, and GFCI protection where outlets are added.
Why do LED fixtures fail early?
Heat and poor drivers. Fixtures in enclosed or insulated spaces that are not rated for it run hot and fail sooner.
Is lighting work different in a shop or office?
Yes. Emergency and exit lighting and energy-code controls apply. See commercial electrician.
Talk to an electrician about lighting installation
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