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Thread: Installed new low voltage recessed lights - now switch hums

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    DIY Senior Member taysan's Avatar
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    Default Installed new low voltage recessed lights - now switch hums

    So I'm doing a complete gut-job reno on the bathroom (or rather I'm paying large sums of money to various professionals to do it).

    Previously there were 4 line-voltage 6" recessed lights. I had these switched over to 6 low-voltage 3.5" recessed lights. They are in IC boxes, all made in Canada. Bought from a proper electrical supply company, not Home Depot.

    They were installed today, using the original light switch (standard cheap Leviton switch - not a dimmer). I note now that there is a distinct 'hum' that seems to emanate from the switch when these lights are turned on.

    We're planning on going to a dimmer for these lights. Is there a specific type of switch/dimmer recommended for low-voltage lighting?

    On another switch in the same gang are two regular wall sconces. I want a dimmer on these as well, so I'd like to get two matching dimmers, one for the sconces, one for the 6 low voltage lights.

    Thoughts?

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    Plumber jimbo's Avatar
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    Are the lights just low voltage halogens? Or are they compact fluourecents?

    Low voltage lights have transformers, and these can hum. I suppose that could be reflected back to the switch.


    As for dimmers, you have to add up the total watts and get a dimmer rated to handle at least that much. Remember that most fluorescents cannot be dimmed at all, and those that can, the dimmer must also be rated for that type of ballast. Some dimmers are not.

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    Licensed Electrical Contractor Speedy Petey's Avatar
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    You have to find out from the Mfg what kind of dimmer to use.

    Low voltage has either a magnetic or electronic transformer. Most require a specific dimmer, some do use standard incandescent dimmers.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    If the low-voltage fixtures do require a special dimmer, be prepared for a fairly big premium over a 'conventional' one.
    Most of the manufacturers make compatible dimmers in various styles, so you should be able to get some that match, even if their guts are different.
    Jim DeBruycker
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    DIY Senior Member taysan's Avatar
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    So, a little more clarity

    Humming is definitely coming from the fixtures, not the switch. My mind playing tricks on me.

    The fixtures are Contrast Lighting ISMR3000M air tight IC housings and take MR16 halogen bulbs. I have Turolight bulbs installed. Magnetic transformers I think.

    http://www.contrastlighting.com/en/pdf/ISMR3000M.pdf

    Right now they're installed in an empty gutted room. They have vapor barrier boots over them, but no insulation and the bulbs are just hanging down. I put the fixtures up in the boxes to test the lights. I'm sure they'll be more quiet once the insulation, vapor barrier and drywall is all up.

    That being said I'll get a good dimmer for them. There are 6 lights on the switch at 50w each.

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    DIY Senior Member taysan's Avatar
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    Well, today I learned the hard way how expensive low voltage fixtures can be! Bought a low voltage dimmer, a regular dimmer for the wall sconces and a step down timer for the bathroom fan. $120 for the three of them. $50 for the LV dimmer.

    Glad I'm not doing a whole house. What is the advantage of LV lighting anyhow, or did I just get sucked into 'more expensive must equal better'?

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    Retired Defense Industry Engineer jadnashua's Avatar
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    A LV bulb might last longer, and you may have more choices (but more expensive!) in bulbs, but standard bulbs aren't bad. A LV bulb could be smaller, and therefore more unobtrusive. As you've found, dimming them can get expensive. Some LV fixtures can use standard dimmers, many cannot. I've stuck with line-voltage fixtures except for my under-counter, where I went with a micro track for the small size of the bulbs and fixtures.
    Jim DeBruycker
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    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Senior Member taysan's Avatar
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    Ah well, live and learn. The standard bulbs seem pretty inexpensive - $2.50 each for the ones I have. I'll have to look into what other options there are. They're MR16 50w bulbs.

    I presume I'm not using less electricity, just losing some of it to heat in the transformers? Or do these actuall draw less? Not that I'm expecting a drop in my electrical consumption from 6 fixtures

    The two dimmers are going into a gang of 3, with a fan timer in the middle. I understand grouping dimmers in a single gang requires a drop in the number of total watts on the dimmers. In my case I've got 6 50v LV on the one dimmer, and 2 line-voltage wall sconces on the other. I think I'm still good even with the drop needed.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    Almost all of the LV lamps use halogen bulbs which give more lumens/watt verses a standard incandescent, but there are line voltage halogens, too, just not as many sizes.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by taysan View Post
    I just get sucked into 'more expensive must equal better'?
    Yep this sounds like the the truth

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    DIY Senior Member taysan's Avatar
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    Well, that's the story of my life.

    I installed the Lutron LV dimmer, fan timer and line-voltage dimmer today. Very nice controls I must say. And the LV dimmer is great - the lights go WAY down to almost nothing. Seems to be less humming now. Just your typical 'buzz' at mid-dim on the lights. Better bulbs might help with that.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    The design of the filaments and how they are supported can make a big difference on how quiet the bulb is. It also depends on the way the dimmer decreases the voltage to the bulb. Some make a very ragged signal approaching a square wave. A sine wave is much less likely to cause ringing from the filaments than a square wave input.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    In the Trades Bob NH's Avatar
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    Quote Originally Posted by taysan View Post
    Well, today I learned the hard way how expensive low voltage fixtures can be! Bought a low voltage dimmer, a regular dimmer for the wall sconces and a step down timer for the bathroom fan. $120 for the three of them. $50 for the LV dimmer.

    Glad I'm not doing a whole house. What is the advantage of LV lighting anyhow, or did I just get sucked into 'more expensive must equal better'?
    Try putting a standard dimmer on the line side of the transformer. A transformer produces a voltage ratio so reducing the voltage on the input side reduces the voltage on the output side.

    Most solid-state dimmers chop the sine wave so you will have some high frequency components in the power to the transformer, but since you are adjusting the dimmer by watching the light it should work. If it doesn't work haven't lost a whole lot.

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    DIY Senior Member taysan's Avatar
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    Well, it's a couple of weeks in, and the humming is bugging me!

    I'm going to check in with my electrical supply place and the manufacturer. I'm wondering if I can go to line-voltage fixtures in the IC boxes that the low voltage fixtures pop into.

    The box itself has the wiring connection and a heat sensor (removeable). The light fixtures connect with a little snap plug and then pop up into the 3.5" holes like any recessed fixture.

    If line-voltage fixtures will eliminate the hum, I may just do that even if 120v MR16 bulbs are a little harder to find. When I find them I'll just buy 60 of them for my 6 fixtures

  15. #15

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    Have never used your brand, but we have many LV Lightolier fixtures installed, mr16 50w with dimmers, can't hear a one of them.

    You did say that you have an empty room, no drywall or insulation, is that still the case? You will find a dramatic change when they are covered, and surrounded with insulation.

    I doubt very much that the bulbs are the problem. A noisy transformer will resonate through the fixture frame.

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