7-50W 12V MR 16 lamped fixtures on a Juno Flex 12 Trac all went out after working fine 4 yrs. Transformer is buzzing when swithed on at either Lutron SLV-603P or other 3-way switch. Other switch does not contro dimming. Transformer ahs had a 60Hz buzz since new. Identical transformer controlling separate Juno Flex 12 Trac with 4 50W 12V M 16s never hummed/ buzzed since both were new SEpt. 2006. Transformer is Juno 310-0007 (label on transformer) 300W transformer- Fox Elec. TF5300BL

Hi John, I'm an electrician and I think I can help you with this problem.

First and foremost, this switch's 2000VA / 1600W electrical rating is based on a incandescent load.

Let's do do the math on this one.. 18 x 50 = 900 watts. So, you're under the 1600 watt capacity, but I think this is a bit more involved than this.

I'd be willing to bet that you're not dimming a 12 volt circuit - but rather a 120 volt circuit that supplies one or more transformers that step the power down from 120 volts to the the 12 volt bulb voltage. A transformer is an inductive load. A transformer's inductive load is completely different than the incandescent load the dimmer is designed to control. The transformers are rated for 120 volts and will have issues including heat problems if provided less than the rated input voltage to provide a reduced output voltage you want so that you can dim these lights.

This switch will not work on the output of the transformer in this situation either because the significant amperage being switched here. Each of these lamps draws a bit over 4 amps as determined by ohm's law: 50W / 12V = 4.16A. The total load at 12 volts is (again, Ohm's law) 18 x 4.16A = 74.88A ! That means the wire would need to be a #4 or #2. This is about the size of the cable on your car's battery (only amperage determines conductor size - voltage determines insulation).

A dimmer on this circuit will not work unless the fixtures are changed so that no transformers are used to supply the lamps. This includes fluorescent lamps (compact or otherwise) unless the packaging specifically states that they can be used on a dimmer.

You may wish to contact Lutron Hotline at 800-523-9466 for additional help and suggestions. I hope this helps & good luck!

if fixture is as shown, remove the nut in the middle of the fixture, remove the lamp, and replace it, note donot touch the lamp with your fingers, this causes lamp to fail, use a cloth to install then replace in reverse as you took it apart

The LED light bulbs operate at 3 to 5 V usually. The noise your hearing is a result of the voltage reduction within the internal workings of the lamp base. The lamps should be installed with an
LED driver vs a transformer power supply.

This is usually on most packaging:

LED MR16 lamps operate in the same fittings as regular 12V lamps. However, they work best when they are mated with an led driver in place of the transformer.
Example of an LED driver:
http://www.google.com/products/catalog?hl=en&safe=off&rls=com.microsoft:en-ph&q=LED+Driver&um=1&ie=UTF-8&tbm=shop&cid=16162019396751156854&sa=X&ei=HzQpTqOWOK_NmAX0-LWqDA&ved=0CEcQ8wIwAg#

The noise will not go away unless you use an LED driver with the MR16 lamps.

Thanks for choosing FixYa.
Kelly

Your issue is that the dimmer is not rated to handle the type of fixture/lamps its controlling.

From a lighting control standpoint, the 12V-lamps classify as "low-voltage halogen" and, somewhere in that circuit, have a transformer(s) converting the 120V~ down to 12V~. Using incandescent dimmers (like the one you are using) can cause compatibility issues with those transformers. What I suspect is happening is that the incompatibily is either throwing voltage spikes or current spikes on the line which are causing the dimmer to enter some sort of "safety" mode to shut everything down before any problems occur.

My recommendation is to first figure out what type of transformer it is: Either magnetic low-voltage, or electronic low-voltage. Ideally you would contact the transformer manufacturer (or look up their specs online) to figure that out. Other rules of thumb: if the transformer's big & bulky, it's probably magnetic - conversely if its lightweight, it's probably electronic. If its only one transformer controlling all of the lamps together, it's probably magnetic - conversely if its one of those transformers where the transformer and light bulb come togheter as one assembled unit and then snap into the track, it's probably electronic.

Then make sure the dimmer is rated for magnetic low-voltage, or electronic low-voltage (depending upon what the transformer is).

When you say "halogen bulbs," are you referring to MR-16 (12-Volt) lamps off a transformer, or line-voltage halogen lamps. If using the MR-16s, then the fixture doesn't qualify as "incandescent" which is what the dimmer you have is rated for, and the behavior of the transformers within the fixture can cause the types of issues you're seeing. If it is a line-voltage (120-volt) halogen then, then it could be a number of things depending upon how "rapidly" and frequent the "up and down" is. Regardless, call Lutron's tech support number at 1-800-523-9466. They're available 24/7, they won't charge you, and they can help you sort this out.

it was a mistake to install them in first place, now, if your transformer blows, that meant that it is overloaded!

primary solutionto the problem, without adding cost of re-wiring will be change globes (50w) to these of lower wattage, say 40w or even less and this will protect transformers from blowing up.

another solution will be to what is load on the transformer, it must be at least 20% greater than combined light supported. if it is not, then duiring power fluctuation it can, and will be burn out.

say, you have 30 lights and 3 switches, this meant that you have three circuits of say 10 lights. 10lights x 50w = 500wat!!! that is rather large and costly transformer, to avoid this prohibitive cost, solve problem otherways, buy 120watt or 150watt transformer and wire two globes to each. this will provide margin as well as enough supply to support your light.

please bear in mind that you are legally not allowed to touch anything what is connected to mains except changing the globe! you need to speak with elelctrician and come to solution in cooperation with eleloctrician.

if you find this advice useful, please do not hesitate to leave comment and vote for me, thanx!

There are two possible problems you could be facing (excluding the transformer going bad) If you have replaced light bulbs with higher wattage ones, you could be drawing too much current through the transformer. (It is common for MR-16 style lightbulbs to be 20w in landscape lights, but 50w for inside lights, and the local hardware store usually only carries the 50w replacement lamps) Each transformer has a specific amount of "watts" it can supply (anywhere from 100w to 1000w) If you exceed the supply wattage of the transformer, the breaker inside the transformer will trip. The quick and easy way to test this is to take a few of the lightbulbs out and see if the breaker will hold.
If you are positive that the total lamp wattage does not exceed the rating of the transformer the second possible problem (but less likely) is that you have a lamp socket or wire connection that is full of water. This water between the two conductors draws current just like a light bulb and can cause an overcurrent fault. This is usually more common if it starts to trip right after a heavy rain when the ground gets saturated with water.

Good Luck!

your new transformer should be fine unless your downlight lamp is 20w,most are 50w 12v so you should check this first.
As for connection your mains supply (primary) connects red to either of the 2 live terminals and black to any of the neutral.The 2 wires from your lamp then go into any pair of the secondary terminals.polarity doesn't matter that is why they are not marked.The transformer can supply 105 w so 2 50w lamps may be connected.
HTH

What is the dimmer rated for? Your load on the track appears to be 200 watts. A standard dimmer will burn out, you need to look on the dimmer to see what it is rated for. Did it run hot with the dimmer before you had this problem? They make dimmers for higher wattage that will do the job for you.

hi alan,

it sounds like the transformer is bad, which makes this easy, time for a new one. 12yrs is a good age for a microwave, average life is about 8-10 yrs!