In my last blog I wrote about the problems I find with the common wall outlet. Now I would like to discuss the wall switch or more specifically the dimmer switch. Before I begin take a moment to read Reuben Saltzman's post on the dangers of dimmer switches with ceiling fans.
The first thing anyone should understand about a dimmer switch is how it works. Essentially the switch is like a valve regulating the flow of electricity to the bulb. The more you close the valve the less electricity flows which makes the bulb dim. With electricity closing or opening of the valve is done by resistance. A consequence of resistance is heat.
Dimmer switches by design are going to get warm, even a bit hot due to electrical resistance. I have on many occasions had a client who is concerned because they noticed a dimmer switch is warm or as I said even hot. Most often this is not a sign of a problem, but normal operation of the dimmer.
Because I have an infrared camera I am able to take accurate temperature readings of a dimmer switch. The infrared image at the right shows a dimmer in operation. The client was concerned because he thought the switch was hot. The cross hairs are the warmest temperature I was able to find after analyzing the image on my computer. The temperature is just over 121 degrees.
What is important to understand is a dimmer switch is made to dissipate the heat produced by its operation. It is equipped with a heat sink, which is the metal seen around the switch in the photo. One of the most important aspects to installing a dimmer is highlighted in the picture. This is where the manufacturer states the capacity of their dimmer switch.
This switch states it has a maximum capacity of 600 Watts for a single switch. That would be six 100 watt light bulbs or other combination equaling 600. It goes on to state if using two switches on the circuit that capacity drops to 500 Watts. With three it goes down to 400.
Exceeding the maximum wattage can cause a fire! The dimmer is not designed to dissipate the heat from over the stated wattage. The lighting on the dimmer in the infrared image was found to be well below the capacity of the switch.
Does it mean if the switch has too much wattage on the circuit you need to call an electrician? Not necessarily. Putting lower wattage bulbs in the lights can correct the problem, but first you need to know the switches rating as discussed above. As with anything electrical if you have one iota of doubt about doing it yourself, call a professional.
One last thing I would add is this; I have heard of instances where various home related professionals have stated that warm dimmer switches are defective or cause for concern. Whether a problem may exist can be fairly easily determined as I discussed. My concern would be has the person making the statement checked all the data.
Temperature is relative. A warm dimmer switch should not send anyone immediately running to the phone to call for help.
James Quarello
2010 SNEC-ASHI President
NRSB #8SS0022
JRV Home Inspection Services, LLC
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