low-voltage pucks causing radio interference

LinelleJanuary 10, 2012

My GC installed low-voltage xenon puck lights under my kitchen cabinets (not my decision, but that's another story). I don't like anything about them and have decided to either replace them with LED light tape OR redo the wiring to 120V and install fluorescent UCL.

This will happen in the next week or so (I'm deciding on which option to choose). In the meantime, I've been turning on the pucks at night and in the early morning so I can see when I'm in the kitchen. This morning, while in my office (not adjacent to the kitchen) I turned on my little plug-in radio as is my morning routine. Horrible buzzing noise. Hmmmm. Only thing I could think of was the pucks. Turned them off, buzzing stopped. On, buzzing returned. They are now staying off.

I don't know anything about electricity and wiring, but it doesn't take a rocket scientist to figure out that it has something to do with the pucks on the new wiring. Is it the wrong transformer? What are the usual causes for this?

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David

The power supply /transformer could be causing radio interference. If so, unfortunately there's little you can do about it.

    Bookmark   January 10, 2012 at 3:56PM
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Linelle

I've decided to have the low-voltage wiring replaced with 120v and will be going with low-profile fluorescent fixtures. Saw two different kinds today (Juno and WAC) and they look awesome, not only the color of the light, but the spread of light from the fixture.

    Bookmark   January 10, 2012 at 4:25PM
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brickeyee

Many pucks use small switching power supplies with minimal filtering.

The radio frequency noise they generate gets is on the output wires and they act as antennas to broadcast the noise.

Try turning the radio 90 degrees.

Most AM radios still use a small ferrite antenna inside the radio, and they are very direction dependent.

If you have noise on the FM band it is getting directly into the radio electronics. Either turn off the lights or move the radio further away from the lights.

There are methods to reduce the noise, but if you plan on replacing the lights anyway there is no reason to spend more effort on them.

    Bookmark   January 10, 2012 at 6:35PM
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Linelle

brickeyee, even though I plan to banish the pucks from my life, I appreciate the helpful info you posted. I had been considering LED replacements, but now I just want the low-voltage wires and transformer gone.

    Bookmark   January 10, 2012 at 7:22PM
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flyfly

It is my understanding that LED lights need a transformer. Some fixtures come with a transformer built in. Others need a transformer added on.

    Bookmark   January 11, 2012 at 10:47AM
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David

This is most likely a case where the transformer / power supply is creating significant RF interference. The best option is to replace the transformer/ power supply.

The device connected to LED lights is not a transformer, but a power supply. Most LED lights out on the market today do not cause RF interference.

There are many devices in homes that require a DC power supply - desktop and laptop computers, alarm systems, ...

Desktop and laptop computers usually have extensive shielding (metal or metallized cases) which cuts down the amount of RF noise emitted.

    Bookmark   January 11, 2012 at 12:52PM
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Linelle

Just bought some low-profile Juno fluorescent fixtures with 3000K bulbs to replace the pucks. Wiring has to be redone, but so be it. These are the fixtures I wanted all along.

All of you have been most helpful and I appreciate it very much. :)

    Bookmark   January 11, 2012 at 3:21PM
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David

Glad it all worked out.

    Bookmark   January 11, 2012 at 3:24PM
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brickeyee

"It is my understanding that LED lights need a transformer. Some fixtures come with a transformer built in. Others need a transformer added on."

Most of the "transformer built in" devices are using a high frequency switching power supply to reduce the size of the unit.

Transformers with 120 V promaries are not small devices, witness the size of even a very low poer 'wall wart.'

The volume of most of them is the actual 60 Hz transformer, and they often cannot even produce 1 amp of output current.

A 10 watt, 12 volt incandescent bulb requires about 0.83 amps.

LEDs are a little better (often being less than 0.10 amps each) but since there are often multiple devices present the actual operating current goes back up.

LEDs often use a combination of series and parallel paths to allow for slightly higher voltages (less drop from the 120 V input) and smaller currents.

    Bookmark   January 12, 2012 at 2:44PM
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Linelle

My Juno fluorescent fixtures just got installed and I am a very happy camper. I've got 34" units centered under 48" cabs, and the light spreads beautifully, filling the deep corners with light. For task lighting, they're awesome.

    Bookmark   January 13, 2012 at 1:46PM
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Johnw1965

There is an option. The Hera Lighting low voltage lights have transformers with RFI (radio frequency interference suppressor). Using a quality product will eliminate the hum. You can find Hera Lighting under cabinet lighting using a Google search.

    Bookmark   June 4, 2012 at 9:01PM
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brickeyee

"The Hera Lighting low voltage lights have transformers with RFI (radio frequency interference suppressor)."

There is no guarantee the suppressor in any particular item will be adequate.

The all have to meet certain FCC rules for radiated interference.

The problem is that radios are designed to capture very small signals.

And better radios tend to be more sensitive and can capture smaller signal.

    Bookmark   June 5, 2012 at 10:45AM
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attofarad

linelle, which model Juno lights did you buy?

    Bookmark   June 6, 2012 at 9:17PM
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