Light Switch Dimmers

Common Dimmer Questions and Problems:

Can you have more than one dimmer in an electrical box?

When you have more than one item in an electrical box it is called ganging. More than one dimmer can generally be mounted in a ganging electrical box. However, it should be noted that this usually decreases the wattage rating of each of the dimmers within the common electrical box. Check the specific manufacturer's specifications for their rules on ganged dimmers.

Does the installation of dimmer save energy?

The simple answer is "YES"! The lower the light level the more energy you are saving, as shown in Table 1.

Table 1 - Energy Savings With Dimmers
Light Reduction	Energy Savings
10%	10%
25%	20%
50%	40%
75%	60%

Does the installation of a dimmer extend the life of bulbs and lamps?

The simple answer is "YES"! The lower the light level the more energy you are saving as shown in Table 2.

Table 2 - Bulb/Lamp Life With Dimmers
Light Reduction	Incandescent Lamp Life Increase
10%	Doubles
25%	Quadruples
50%	20 Times Longer
75%	More Than 20 Times Longer

Initial testing with halogen lamps would indicate similar extended life characteristics to those of incandescent bulbs.

Is a warm dimmer defective?

Electronic dimmers dissipate heat, this is a normal occurrence. The closer the dimmer is to its specified full load, the warmer it will feel. Providing the load (wattage) that the dimmer is controlling is within its specifications, you are safe. Quality dimmers dissipate less than 2% of the energy consumed in heat. However, heat is one of the reasons that the dimmers are derated when ganged (see Question 1).

My bulbs/lamps buzz now that I have installed a dimmer.

Without getting into the detailed technical reasons for the buzzing, this is not uncommon and is caused by the lamp filament vibrating. The buzzing is usually most noticeable at the 50% level. There are four things you can do in an attempt to remove or reduce the buzzing noise.

Use bulbs that are designated "rough service".
Use a bulb that is physically smaller than the current bulb that buzzes.
Use a lower wattage bulb.
Some manufactures supply a device known as an lamp debuzzing coil (LDC) which is installed in the circuit where the buzzing lamp is operating.

My stereo system buzzes after I installed a dimmer.

The better the quality of the dimmer the less likely you will hear a buzzing noise on radios and other communication devices. The buzzing noise is caused by radio frequency interference (RFI) generated by the dimmer. The quality dimmers have electronic circuitry within them that suppresses RFI, but even a high quality dimmer can create buzzing noises under certain circumstances.

There are a number of things that can be tried to eliminate or at least reduce the buzzing noise

Move the affected communications device farther away from the dimmer, at least 6'.
Plug the affected device into a different circuit, that is not the same circuit as the dimmer is on.
Add a power-line filter to the device that is buzzing.
Contact the manufacture.

I have 3-way switches, can I use a dimmer?

Yes. But, you must purchase a dimmer that is designed for 3-way switch applications.

I have 4-way switches, can I use a dimmer?

Yes. But, you must purchase a dimmer that is designed for 4-way switch applications. They are very expensive.

Can I mount my dimmer horizontally?

Refer to the manufacture's specifications. Many dimmer switches are designed to work in a vertical mounting position only.

Dimmer Switch Styles:

The styling of a dimmer switch has little relevance to its load dimming capabilities. The style, which includes the color of the device, provides operational efficiencies and aesthetic value.

While there are common styling's, many manufacturers have their own specific styles. Figures 1 through 7 show a few of the numerous dimmer switches that are available.

Toggle switch with preset dimmer