Halogen Transformer Frequently Asked Questions

Can GE Lightech's electronic low voltage transformers be dimmed using a wall dimmer or a central dimming system?
Yes, all of the electronic low voltage transformers are dimmable.

What type of wall dimmer can I use?
The transformers can be dimmed with any "Trailing Edge" (Reverse Phase or ELV) wall dimmers which are commonly called electronic low voltage dimmers. These can be purchased in most lighting stores/showrooms or from an electrical distributor. These will be harder to find in hardware or home improvement stores.

Are there less expensive wall dimmers available?
Yes. These “Leading edge” (Forward Phase or Triac) dimmers are commonly called incandescent dimmers. These can be purchased in most hardware or home improvement stores. GE Lightech transformers can be controlled with many, not all, of these types of dimmers.

If you want to use these lower cost incandescent dimmers, we suggest contacting the dimmer manufacturer prior to purchase for any recommendations on models to use with an electronic low voltage transformer. Some dimming manufacturers recommend using only electronic low voltage dimmers to dim any electronic low voltage transformer. Any of GE Lightech's transformers can be dimmed with any electronic low voltage wall dimmer ("Trailing Edge").

Can electronic transformers be dimmed if I install a central dimming system?
Yes. Central dimming systems vary in their features and complexity so it is always best to contact the dimmer manufacturer before purchase or installation to let them know you will be using electronic low voltage transformers. The dimming manufacturer can suggest the appropriate dimming modules, wall dimmers, interfaces, etc. for their dimming system. GE Lightech transformers can be dimmed using any Trailing Edge or Reverse Phase control.

What types of lamps (light bulbs) can be used with your transformers and is there a minimum amount of wattage that I need to connect to the transformer?
The transformers are designed to power low voltage (12V or 24V) halogen or xenon lamps.

GE Lightech's datasheets on this website will show the minimum load (wattage) you must have connected to the transformer for proper operation as well as the maximum wattage you can have connected to the transformer.

GE Lightech's LET 60/LW transformer is a 60-watt transformer for 120V input power that only requires a minimum connected load of 3 watts. Some companies are designing very low wattage LED products so they can be powered by electronic transformers. You should not use transformers to power LEDs if the manufacturer does not specifically state that their LED product can be powered with electronic transformers that have a high frequency AC output (between 30-40kHz).

GE Lightech also makes a complete line of power supplies for LEDs. These are often called LED Converters or LED Drivers.

What should I know before wiring the fixture to the transformer?
Be sure to follow the installation instructions that come with the product. Loose connections anywhere on the low voltage side of the transformer will cause transformers to operate at an elevated temperature that may exceed the maximum case temperature of the transformer. This can affect the proper operation and shorten the life of a transformer. When joining two or more wires together you should twist (snake) the wires around each other before placing a wire nut or other type of wire connector over this connection. This “snaking” of wires maximizes the surface contact area of the wires you are joining together for better wire-to-wire contact. If the fixture comes with “terminal block” types of connectors make sure the wires are fully inserted into the terminal block and then tighten the screws to securely grip the wires inside the terminal block.

If your light fixture is a track, monorail or cable lighting system make sure the fixture heads are securely fastened to the rail, track or cables. Check all of the fixture heads whenever you are replacing lamps to make sure they remain securely fastened. Check the lamps (light bulbs) to make sure they are fully inserted into lampholders (sockets) and that the two pins of the low voltage lamps are being firmly gripped by the lampholders. Any lampholders (sockets) that are not securely gripping the lamps and have excessive play should be replaced.

Install all of the lamps in the fixture before powering up the fixture.

I installed a new low voltage lighting fixture and it does not work. What could be wrong?
Be sure to follow the installation instructions that come with the product. This can sometimes occur if the fixture was turned on before installing all of the lamps in the fixture. Try switching off power to the fixture for five seconds and then switching the fixture back on. The transformers have a short-circuit protection feature that will not allow the transformer to supply power to the fixture until the electrical short is removed. Turn off power to the fixture and look for any possible shorts. Inspect the wires coming into and out of the transformer to make sure there are no nicks in the wire insulation as a result of wires being pinched inside part of the fixture. Closely inspect the fixture for possible shorts. Check your wiring connections again. Switch the power to the fixture back on to see if this solves the problem.

Why would my light fixture be cycling on and off?
This is common when the transformer reaches an extremely high temperature. This is not a normal condition. The transformer has a thermal cut-off protection feature that shuts down the output of the transformer when it reaches an extremely high temperature. When the transformer has cooled to a normal operating temperature the protective feature will allow the transformer to power the fixture again. The cycling is an indication the transformer is repeatedly reaching an extremely high temperature and this requires an inspection of the wiring connections and the fixture. Do not continue operating the fixture in this condition for an extended period of time.

Fixture manufacturers usually perform a heat test of the transformer when it is inside their fixture. This heat test may determine the maximum wattage rating of the fixture and the maximum wattage per lampholder (socket) to ensure the transformer does not exceed its maximum case temperature when it is enclosed inside their fixture. This is why the maximum wattage rating of the fixture might be lower than the maximum wattage of the transformer. Add the wattages of all the lamps in your fixture and make sure this total wattage does not exceed the fixture manufacturer's maximum wattage rating.

If you have installed a GE Lightech transformer into a fixture that came from the manufacturer with a different transformer inside, the GE Lightech transformer could be exceeding its maximum case temperature when enclosed in the fixture. Reducing the connected wattage (load) will reduce the operating temperature of the transformer. Another common cause for the transformer to operate at a very high temperature is loose connections anywhere on the low voltage side of the transformer.

My voltmeter gives an accurate measurement of the input voltage coming into the transformer but my voltmeter measures no output voltage or an abnormally low output voltage from the transformer.
First, you must make sure that a lamp load (the fixture with light bulbs) is connected to the output side of the transformer before turning on the power to the transformer. Some transformers will not produce any output voltage unless the lamp load is connected prior to applying power (switching on) to the transformer. If power to the transformer is switched on first and then lamps are inserted into the fixture sockets you may not get any output voltage until you turn the transformer off for 3-5 seconds and then switch it back on again. This is a protection feature in the transformer.

You will not read any output voltage from the transformer if there is a short anywhere on the low voltage side of the transformer or in the fixture. The short-circuit protection of the transformer will shut down the output voltage of the transformer until the short is removed. A simple way to isolate the transformer for testing is covered in the next question.

Electronic transformers have a high frequency output that cannot be accurately measured unless the meter is a True RMS meter that is capable of reading the high frequency output of electronic transformers. You may have an expensive meter but it may not have this measurement capability. GE Lightech's transformers have an AC output that is between 30-50kHz. A True RMS meter that can read up to 50kHz is required to get an accurate voltage reading on the output side of the transformer.

I am an electrician but I don't have a meter to properly measure the output voltage of electronic transformers. How can I test the output of the transformer without one of these meters?
GE Lightech's transformers for use in North America:

North American transformers with a 120V input voltage are used in residential applications and some commercial buildings. Transformers with a 277V input voltage are used in commercial buildings. The input wire colors (high voltage side) are (1) black wire and (1) white wire. The output wires (low voltage side) of the transformer connect to the lighting fixture. The two wires having the same color (two blue wires for 12V versions or two purple wires for the 24V versions) are the output wires.

GE Lightech's transformers for use in countries outside of North America:

Many European and Asian countries have 230V or 240V electrical systems. In these countries the wire colors are different. GE Lightech's transformers input wire colors (high voltage side) are (1) blue wire and (1) brown wire. The other two (2) wires are the output side (low voltage side) of the transformer and those wires are used to connect to the fixture. You can verify this on the label to determine which end of the transformer is the low voltage side and which end is the high voltage side.

Once you have identified the two (2) low voltage wires of the transformer you can try a simple test method to isolate the transformer to determine if the transformer is working and if the transformer is providing adequate output voltage. With power to the fixture turned off, remove one of the lamps (light bulbs) from one of the lampholders (sockets) of the fixture. Connect the two (2) low voltage wires of the transformer to the two pins of the low voltage lamp. Turn the switch on and if the transformer is working, the lamp should light in less than two seconds. If the lamp is bright or “white” in appearance you know the transformer is providing adequate output voltage.

The various transformer models have a minimum wattage that must be connected to the transformer for proper operation and this could range from 10W-35W watts for the lower wattage transformer models. A minimum connected load of 50W-75W is required for the 150W-300W transformer models. For this test method to work you must have a lamp that is close to the minimum load requirement of the transformer you are testing. With a 50-watt lamp you can test most of GE Lightech's transformers using this method. Low voltage lamps reach a very high temperature in a short period of time so be sure not to handle the lamp with your bare hands.

My light fixture sometimes dims by itself and then returns to a normal light level. Why would my fixture be doing this?
If the transformer reaches a high temperature the transformer will dim the light fixture by reducing the output voltage of the transformer. This dimming is proportional to the rise in temperature above the maximum case temperature rating of the transformer. This is an auto-thermal regulation feature on many of GE Lightech's transformer versions (not all) that is a patented protection feature.

Add the wattages of all the lamps in your fixture and make sure this total wattage does not exceed the fixture manufacturer's maximum wattage rating.

Why would I measure no output voltage on my meter from a new transformer?
First, you must make sure that a lamp load (the fixture with light bulbs) is connected to the output side of the transformer. Connect the lamp load before turning on the power to the transformer. Some transformers will not produce any output voltage unless the lamp load is connected prior to applying power (switching on) to the transformer. It may also be the type of meter that you are using.

If I use one of your AC transformers how far can I put the transformer from the fixture or lamps that I want to power.
Electronic transformers with 12V AC output are used for shorter distance applications and there are some recommended distance guidelines. For transformers of 200-watts or less with a 12VAC output, you will want all lamps (light bulbs) to be within ten (10) feet of the transformer. For 300W transformers with 12VAC output this distance should be kept to five (5) feet. The distances include the total length of wire and/or fixture to the lamps you are powering. If you use a transformer with a 24V AC output you can multiply the distances by four. A 300W transformer with a 24V AC output can be used at twenty (20) feet and the 300W transformer with a 12V AC output can be used at five (5) feet. Do not use a transformer with a 24V output to power any 12V halogen or xenon lamps. Use 12 gauge (12 AWG) stranded copper wire to connect the output wires of the transformer to the fixture or to the lamps you are powering.

I see that you have a separate category for Class 2 transformers for 120V power. What is a Class 2 transformer?
Class 2 transformers are limited to 5A (amps) of current on the low voltage side of the transformer and this is considered inherently safe. You may not be required to encase or install the low voltage wiring in conduit by many local building inspectors but each local authority can be different