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Lutron Lighting FAQ


What makes the light dim?

The triac is the key to dimming. This dimmer component actually turns the light on and off very rapidly - 120 times per second. This technology is illustrated below.

dimming diagram

The longer the light is ON versus OFF (example A) the brighter the light output. By the same logic the longer the light is OFF versus ON (example B) the lower the light output.


How do dimmers save energy?

When the light is off, no energy is being used. The longer the triac is off, the lower the light output, and the greater the energy savings.

Lutron Dimmers Pay for Themselves:
Dimming the lightsSaves electricityMakes incandescent bulbs last longer
10%10%2 times longer
25%20%4 times longer
50%40%20 times longer
75%60%> 20 times longer


If the lights are being turned on and off won’t the lights seem to be flickering?

No. No matter how bright or how dim the light level is constant and smooth. The human eye has a built in persistence to see things after they go away. An example of this is in movies where the film is projected on the screen many times a second.


Doesn’t turning the lights on and off so quickly decrease bulb life?

No. Switching the bulb does not decrease bulb life; heat decreases bulb life. By reducing heat, bulb life is increased.


Can Lutron dimmers be ganged?

Yes. When 2 or more dimmers are in the same wallbox, they are considered “ganged”. To install ganged dimmers, simply remove the dimmer side sections from the heat sink. The maximum wattage capacity for each dimmer is reduced (derated) so that the dimmer does not overheat.


Should I use quiet, or fully variable fan controls?

Quiet fan control- If the application is one celing paddle fan, a quiet (step) fan control is the best choice. Quiet fan-speed controls will not cause fan-motor hum, making them ideal for bedrooms, children’s rooms, media rooms and other locations where noise is particularly important.

Fully variable fan control- Although fully variable (full range) fan-speed controls are an option for conrolling one single ceiling paddle fan, they are the only choice for controlling more than one ceiling paddle fan, bathroom, whole-house/attic, range hood, agricultural fans and heat exchangers.


Can neon/cold cathode lamps be dimmed?

Yes. By using the proper equipment neon/cold acthode lamps can be successfully dimmed. Lutron Nova® low voltage dimmers and GRAFIK Eye® controls are UL listed for neon/cold cathode loads. All Nova® low voltage dimmers require a neutral wire.


Does dimming affect halogen lamp life?

Yes, dimming increases incandescent lamp life. Halogen lamps are incandescent lamps with a tungsten filament. Lutron’s pilot test data suggests that halogen lamps will have an expected lamp life similar to other incandescent lamps when dimmed. As an example, one type of halogen lamp with a rated life of 2000 hours dimmed to 80 volts has a life extension of at least 5 times. Lutron is continuing testing with various halogen lamps.


What do I do when I need more wattage than that for which the product is rated?

Hi-Power 2-4-6™ dimming modules can be added to any incandescent dimmer to increase the load capacity up to 30,000 watts. Lutron also provides GRAFIK Eye® dimming panels for load capacity up to 144,000 watts in one panel.


Why do dimmers get warm, and is this safe?

The technical explanation. During normal operation, solid-state dimmers generate heat. A solid-state dimmer is roughly 98% efficient-2% of the power dissipates as heat, causing the dimmer to feel warm to the touch. The closer a dimmer is run to full output and the higher the load (watts) on the dimmer, the warmer it will feel.

This is perfectly normal and safe. Lutron dimmers are designed to the strictest UL safety standard, and can handle their full rated load. (a 600W dimmer can handle a full 600W of power*. Without overheating.)

*Dimmers that are ganged together in a common wallbox may need to be derated.


Why do I have trouble dimming my Phillips Masterline™ lamps?

These lamps contain a diode which may interfere with proper dimming performance. Lutron Electronics does not recommend dimming these lamps. Diode lamps possess either negative or positive polarity, however, the lamps are not marked to indicate whether they are positive or negative. Unsatisfactory dimming performance can occur if the dioded lamps in a circuit have the same polarity (i.e., all positive or all negative). Under these conditions, the lamps will flicker and will not dim below approximately 50%. Lutron recommends that you try one of the following suggestions:

  • 1. Replace one lamp in the circuit with a lamp of opposite polarity. As long as there is at least one positive lamp and one negative lamp in the circuit, no problems will occur. Since the lamps are not marked as to their polarity, some trial and error may be required to find a combination of lamps that works properly.
  • 2. Use a dimmer with neutral connection, such as the Nova® low voltage series (NLV-600, NLV-1000, NLV-1500). The neutral connection allows the dioded lamps to dim normally. This solution is also suggested for circuits with only one dioded lamp.
  • 3. The Phillips trade name for this bulb is Masterline™. Phillips has plans to remove the diodes in the near future.

Why does my lamp buzz?

Occasionally, you may sometimes notice that a lamp is buzzing. This is caused by the lamp filament vibrating as the dimmer rapidly switches the lamp on and off. Lamp buzz is generally noisiest at the mid-rnge (50%) dimming level. If this happens, use rough service lamps (sometimes called garage door opener lamps), physically smaller lamps or lower wattage lamps.

The most effective way of reducing lamp buzz is to install a lamp debuzzing coil (LDC) in the lighting circuit. When an LDC is wired in series with the dimmer, it slows down the inrush of current during the rapid switching cycle of the dimmer. As the current inrush is slowed down, the lamp filament vibration and lamp buzz are reduced.

Lutron has two LDC models available to help reduce lamp buzz. The type of LDC required depends on the total wattage of the dimmer’s lighting load. Listed below are the model numbers and their respective capacities.

Model#:Rated Capacity:

LDCs may be wired in series with the dimmer on its line side or load side. Each dimmer requires its own LDC.

LDCs themselves make an audible buzz, and therefore, should be mounted in an area where the noise will not be objectionable (e.g. an electrical closet, a basement or above a drop ceiling). The LDCs are UL listed and thermally protected.


Why do my lights flash or suddenly change levels?

You may be experiencing a common neutral interaction. Common neutral interaction is cross talk between dimmers that share the same neutral wire. This may cause the lights to flicker, flash or suddenly change intensity. When solid-state dimmers are operating, voltage spikes occur and are transmitted onto the neutral wire. Normally this is of little concern, except when the neutral wire is common to two or more phases of 120/208V, 3-phase, 4-wire system. Under this condition, the voltage spikes may feed back to the dimmers via the common neutral wire, causing interaction between the dimmers.

Lutron recommends the following methods to avoid common neutral interaction:

  • A. Separate neutrals
  • B. Filter choke
  • C. Special Lutron dimmers

Filter Chokes
If it is not possible to run separate neutrals for each phase (e.g. an application with existing wiring), you can use filter chokes to “clean up” the voltage spikes creating the interaction. One filter choke is required for each dimmer. The filter choke makes an audible buzz, so care should be taken to mount it in an area where the noise will not be objectionable. Filter chokes can be wired in series on either the line side or the side of the dimmer.

Special Dimmers
If it is not possible to run separate neutrals or use filter chokes to correct the interaction, the following special dimmers are available from Lutron to accommodate common neutral applications:

Model#:Max. Load Capacity:

Note: All models are for incandescent lighting and are available in Nova® style only.


What is radio frequency interference (RFI)?

RFI is a buzzing noise which may occur in some audio and radio equipment when solid-state dimmers are used nearby. Although every Lutron dimmer contains a filter to suppress RFI, additional filtering may be required in some applications. Typical examples of RFI-sensitive equipment are AM radios, stereo sound systems, broadcasting equipment, intercom systems, public address systems and wireless telephones.

RFI can be transmitted in two ways:

  • Radiated
  • Conducted

Note: The suggestions in this application note will help minimize RFI; however, they do not guarantee that RFI will be completely eliminated.

Radiated RFI
Any sensitive equipment that is in close proximity to dimming equipment can pick up the RFI and generate noise into its system.

The following are three possible ways to minimize the radiated RFI:

  • Physically separate the RFI-sensitive equipment from the dimmer and its wiring.
  • Run dimmer wiring in its own metal conduit.
  • Use a lamp debuzzing coil (available from Lutron) to filter the RFI.

Conducted RFI
In some cases, RFI is conducted through the building wiring and directly into the AC power supply of the sensitive equipment.

To minimize the conducted RFI, follow these guidelines:

  • Feed sensitive equipment from a circuit without a dimmer on it.
  • Add a power-line filter to the sensitive equipment.
  • Add shielded wire for all microphones and input cables. Also, use low-impedance balanced microphone cables, which are less susceptible to interference than high-impedance types.
  • Make sure all the equipment is grounded. Connect all shields to the ground at one point. Ground lighting fixture metal housings properly.
  • Use a lamp debuzzing coil (available from Lutron) to filter the RFI.

Lamp Debuzzing Coils
Lamp debuzzing coils (LDCs) are the most effective way to reduce RFI. One LDC is required for each dimmer. Select the LDC according to the connected lighting load. The LDCs may be wired in series on either the line side or the load side of the dimmer. For maximum RFI suppression, keep the wiring between the LDC and the dimmer as short as possible.

Since the LDC itself make an audible buzz, mount in a location where the noise will not be objectionable (e.g., an electrical closet, a basement or above a drop ceiling). LDCs are designed to easily mount onto a standard 4"x4" junction box. They are UL listed and thermally protected.

The following LDCs are available from Lutron:

Model#:Rated Capacity:

How can I minimize radio frequency interference?

Radio Frequency Interference (RFI) occurs when solid-state dimmers emit noise that interferes with AM radios, audio equipment, etc. Every Lutron dimmer includes radio frequency interference suppresion circuitry. Additional filtering may be required in some applications. In instances where interference does occur, Lutron recommends the following:

  • Ensure there is 6' (2m) between the dimmer and audio equipment
  • Place the dimmer on a separate circuit than the audio equipment
  • Run dimmer wiring in its own metal conduit
  • Use a lamp debuzzing coil to filter the RFI
  • Purchase an in-line filter for the audio equipment
  • Use an electronic low-voltage dimmer (requires a separate neutral wire) for incandescent loads

Will Lutron dimmers affect high-end output?

When the Lutron dimmer is set at full, most users will not notice a difference from a switched light. A light meter will register a slightly lower high-end output, as Lutron dimmers automatically save electricity and make incandescent bulbs last longer.


How do I tell magnetic and electric low-voltage transformers apart?

Transformers may have magnetic (core and coil, toroidal) or electronic (solid-state) clearly indicated on the product. However this is not a required marking and will not be found on all products.

The best way to determine transformer type is to contact the manufacturer.

A hint of the transformer construction can often be found in the transformer’s weight. Magnetic (core and coil, toroidal) transformers are often heavy for their size. Electronic (solid-state) transformers tend to be smaller and are often light for their size.


What do I use for self ballasted 'dimmable' compact fluorescent lamps?

Lutron does not currently offer any products UL listed for these devices. For fluorescent dimming, use a Lutron electronic fluorescent dimming ballast and a dimmer specifically UL listed for use with that ballast.


What is common neutral interaction?

Common neutral interaction occurs between at least two dimmers that share the same neutral wire. When solid-state dimmers are operating, voltage spikes occur and are transmitted onto the neutral wire. Normally this is of little concern.

When the neutral wire is common (to two or more phases of a 3-phase, 4-wire system) the voltage spikes may feed back to the dimmers. The common neutral wire can cause interaction between the dimmers that are on different phases.

Folowing are symptoms of common neutral interaction:

  • Lights flicker at certain dimmer settings
  • Lights flash to full output at certain dimmer settings
  • Light level of a dimmer on one phase inadvertently changes when a dimmer on another phase is adjusted

Lutron recommends the following methods to avoid common neutral interaction:

  • Run separate neutral wires for each dimming circuit, from each dimmer’s load to the distribution panel
  • Install a lamp debuzzing coil
wiring diagram

Can I use a 3-way dimmer in a single-pole application?

Yes. If a product purchased as a 3-way control needs to be used in a single-pole application, cap off one of the traveler wires with a wire connector.

wiring diagram

Can I use a 3-way dimmer in the 4-way switch location?

No. 3-way dimmers may only be located in either of the 3-way switch positions.

wiring diagram

Can I use a standard 3-way switch with a multi-location dimmer?

No. Multi-location dimmers do use standard 3-way wiring, but make use of one wire for communications while the other carries the load current. A 3-way switch is not compatible with this.

wiring diagram

What is a FASS™?

All Lutron dimmers have an air-gap off. Typically this is integrated into a slider or paddle switch. Some dimmers have electronics that stay active when the lights are off, such as an infrared receiver. For these products, the air gap is activated by a separate Front Accessible Service Switch (FASS). When open, the FASS completely disconnects the power to the load. This ensures that there is no leakage current to the fixture during routine lamp maintenance. In addition, when the FASS is open, no remote locations (3-way, etc.) can re-energize the circuit.


There is no ground wire in the box, what do I do with the green wire?

When no grounding means exists within the wallbox, the 2002 NEC article 404.9 exception to (b) permits a dimmer without a ground connection to be installed as a replacement. For this type of installation, cap or remove the dimmer ground wire. A dimmer installed under this exception must be provided with a plastic, noncombustible wallplate (all Lutron plastic wallplates meet these requirements).


Why are some dimmer wires not copper colored?

Lutron uses tinned copper wires on some of our products. These wires are silver in color as a result of the tinning process. Tinned copper wires are compatible with copper wiring and wire nuts. Lutron uses tinned copper wires to avoid stray strands and to make our products easier to install.


Why are there 2 wires on one of the terminals of my single pole switch?

One of the 2 wires is a “continued hot” for a branch circuit. Keep these wires together and connect both to one of the wires on the dimmer.


Will a fan/light control work with existing wiring?

The fan light control requires separate wires to the fan and light and a 120 volt hot wire. Unless your house was specifically wired for fan light controls, additional wiring will need to be added.


What is the “common terminal” on a 3-way switch?

The common terminal is the different colored screw (not the green).


Why doesn’t my Accessory Dimmer work? The Smart Dimmer operates the lights properly.

Reverse the connections on the Smart Dimmer. (Swap the black and red wires with the connectors from the wallbox) It is on the load side of the circuit.


How do I eliminate buzz with a magnetic low voltage fixture?

If the fixture has a toroidal type transformer (looks like a donut with wires wrapped around it) use a dimmer with a neutral wire such as NLV-600. If your fixture has a “core and coil” transformer (square and heavy) use a lamp debuzzing coil.


What should I use to clean my dimmers?

Use only a damp soft cloth. Chemical cleaners can damage plastic.


Why does my 4-way switch have 4 wires and the Accessory Dimmer that replaces it only has 3 wires?

The blue wire of the Accessory Dimmer connects to 2 of the wires from the switch as shown in the instruction sheet.


Can I dim a 4-way circuit?

Yes, a 3-way dimmer will replace one of the 3-way switches. A 4-way circuit can be dimmed from all switch locations by using a Multi-Location dimmer and 2 Accessory Dimmers such as Maestro, Spacer, Spacer System or Faedra.


Can I use a Quiet Fanspeed Control on 2 fans if the total is less than 1.5 amps?

No, a Quiet Fanspeed Control can only be used with 1 ceiling paddle fan.


Why are my energy saving or screw in fluorescent lamps dropping out at low end or flickering?

These lamps, whether they be termed energy saving or otherwise are really fluorescent lamps at their heart. Even the ones marked or packaged as dimmable generlly exhibit problems with light levels dropping off suddenly when dimming down or there can be flickering throughout the dimming range. Lutron does not recommend using these bulbs and reminds you that you are already saving energy when dimming your regular incandescent lights.


Why can’t I mount my dimmer horizontally in my wall?

Lutron dimmers are designed and tested to be installed and operated only in the mounting position (vertical) as indicated on the dimmer.

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