I have several dimmers all over my house. The ones used on the home automation system are Leviton. Others that are not part of the home automation system are Lutron.
The majority of the lighting is still incandescent BR30 65 watt 130V lamps. Do those dimmer loads radiate/emit RFI through the air and onto other near by branch circuit wiring? You bet it does. Through the air at least 4 to 5ft until it starts to dissipate.
Just recently I installed LED, 85 watt equivalent incandescent, lamps in the can lights in the kitchen. I installed a Lutron 3way dimmer to dim the lights down as needed.
With a total of 7 dimmers for incandescent and one LED I can not detect any change in my 2 channel audio system or my HT system whether the dimmers are on or off.
With one exception. I have a separate audio rack in my audio room, with some old vintage 1970s equipment setting on it that is about 3ft from a Lutron dimmer. Even though the branch circuit the equipment is plugged into is different than the lighting circuit, the equipment is within the radiated RFI field of the dimmer as well the branch circuit the equipment is plugged into. The branch circuit wiring feeding the audio equipment is also infected by the Dimmer RFI.
When listening to a, vinyl record, CD, or Cassette tape, I do not hear any noise. It is quite noticeable if the tuner is used on the Marantz 2252B receiver though. Especially the AM band. LOL though, who listens to AM radio anymore?
IF you have dimmers in your home here is what you need to do when installing a new dedicated branch circuit/s for your audio system or HT system. KEEP the new dedicated branch circuit wiring as far as possible from any dimmer branch circuit wiring. Especially the load side wiring of the dimmer that feeds the lighting loads.
As for the line side feeding the dimmer I have found the dimmer RFI starts to dissipate the further you get away from the dimmer going toward the source, the electrical panel, the branch circuit is fed from. Is it still at the electrical panel? Yes somewhat but a whole lot weaker. And I found even weaker yet the farther you get away from the breaker/s feeding the lighting circuits the dimmer/s are fed from.
For my 2 channel audio system I kept the two 10-2 with ground NM-B cables, (Romex is a trade name of NM cable), as far away from parallel lighting branch circuits as possible as soon as I could after getting out of the electrical panel. I also kept the two dedicated circuits separated from one another by at least 2ft. The length of the dedicated branch circuits are about 75ft from the electrical panel to the wall duplex receptacle outlets. At the receptacles I can not detect any discernible dimmer RFI noise. The audio system is dead quiet.
IF it is not possible to keep a new audio dedicated circuit away from existing lighting circuits that have dimmers then you could use MC aluminum armor cable. The armor should/will shield the dedicated branch circuit wiring from the outside radiated dimmer RFI.
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I ran across this Lutron article doing a web search.
Minimizing Radio Frequency Interference (RFI)
Application Note #519
Revision D
June 2014
A solid-state dimmer is an electronic switch that rapidly turns the current on and off 120 times per second to achieve the dimming effect. This rapid current switching may cause radio frequency interference (RFI) — an audible buzzing noise — with sensitive audio and radio equipment. Although every Lutron® dimmer contains a filter to suppress RFI, applications with sensitive equipment may require additional filtering. 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
Radiated RFI
All wiring that carries dimmer-controlled current can act as an antenna to radiate RFI into the air waves. Any sensitive equipment that is in close proximity to this wiring can pick up the RFI and generate noise into its system. Also, this could occur if the wiring for sensitive equipment runs along side the wiring for the dimmer.
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https://www.lutron.com/TechnicalDocumentLibrary/360484.pdf//
Check out this interesting video on dimmer RFI harmonics.
https://www.youtube.com/watch?v=OCK5W9vlAE0