RE: Noisy dimmer switches and RFI

["Keith Doxey" <lists.diyha@xxxxxxx>]

Hi Tracey,

 

Any dimmer will generate noise. It is caused by chopping up the mains and suddenly applying current. It can be lessened by the judicious use of chokes to limit the rate of rise of current thereby limiting the magnetic field created. Better dimmers have larger chokes.

 

One way of trying to minimise the interference is to ensure that Live and Neutral follow the same path (something that doesnt always happen with house wiring) thereby creating a balanced circuit. Because the conductors are in close proximity and carrying identical but opposite currents the radiated magnetic field will be effectively cancelled.

 

The majority of interference is radiated by the WIRING not the dimmer. The dimmer is the cause but it is worsened haveing a bloody great aerial attached !

 

Keith

-----Original Message-----
From: Tracey Gardner [mailto:tracey.gardner@xxxxxxx]
Sent: 07 March 2002 13:45
To: ukha_d@xxxxxxxSubject: [ukha_d] Noisy dimmer switches and RFI

With reference to the attached, is it possible to get these
Lutron
dimmers in the UK, or has anybody got any suggestions about
"clean"
dimmers that are available in the UK?

Tracey

>>
>> Are there any particular brands or specific models of dimmer
>> switches(!!) that don't pollute our low frequency bands with
RFI?
>>
>> 73,
>> Charlie, N0TT
>>
>Yes, there are. The problem is that there are so many styles and
models of
>dimmers---rotary knobs with switches at the CCW end or with
push-in
>switches, sliders with or without switches, and toggles. There
are single
>and double pole dimmers, 600W and 1000W (and more) dimmers,
dimmers for
>low-voltage lighting, designer dimmers, and so on. I think you
get the
>picture.
>
>Generally, the "good" units include small ferrite beads and
maybe
>capacitors, and often the product description will mention the
RFI
>protection in some way. Unfortunately, such switches often have
a (small)
>added cost increment--so most people, unaware of what RFI is and
why they
>should be concerned, buy price and get the cheapest units from
Ace Hardware.
>
>Several years ago, I made up a test jig with a bunch of
different dimmers
>and a 100W bulb, and put a portable AM radio next to the kludge.
To achieve
>a meaningful comparison, all were single-pole, rotary knob, 600W
>incandescent units---the most common denominator. I think I had
a
>representative sampling---by no means was it comprehensive.
>
>The difference between these dimmers in terms of RFI was quite
>significant---stunning, really. My hands-down favorite for a
plain vanilla
>rotary 600W single-pole incandescent application was and is the
Lutron
>"Traditional" D-600 series. Lutron claims "superior radio
frequency
>interference (RFI) filtering" and I agree.
>
>I have since placed a half-dozen of these in neighbors' homes.
To find the
>offending RFI generator, I walk the neighborhood with a portable
AM radio
>tuned to the top of the BC band. The buzzer will often just leap
out at me
>as I walk past a house. Most folks, when I explain my mission,
allow me to
>replace their units, but there is a possible liability factor
involved in
>not being a licensed electrician.
>
>W.W. Grainger sells the D-600's for $5.14 in singles. Their
stock number is
>4LX92 (white) or 4X603 (ivory). The 3-way versions are the D-603
series:
>Grainger numbers are 4LX93 (white) and 4X852 (ivory) @ $7.84.
>
>There are also Lutron toggle (AY-600 single-pole and AY-603
3-way) and
>slider (GL-600 single-pole and GL-603 3-way) units in that
series. These
>cost a LOT more ($12.12 for the GL-600 to $54.90 for a 1000W
3-way toggle
>unit), so I don't even consider them for freebie replacements.
Ditto the
>"Designer" Series, which run from $16.26 to $91.45! As if these
were not
>enough, there are High Power dimmers (to 2000W) which generally
sell to
>commercial and public space applications and which can cost
hundreds of
>dollars eaach.
>
>The relevant pages in the huge and wonderful Grainger catalog
are 879-882. A
>whole tree died for each one of these.
>
>The standard disclaimers apply---I have no personal interest in
Grainger or
>Lutron. But Grainger is a toystore for adult males, fer sherr.
>
>Aren't you glad you asked? :-)
>
>Garry, NI6T
>




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