Dimming Low-Voltage LED MR16 Lamps

Light Emitting Diodes (LEDs) are replacing traditional light sources in almost all lighting applications, including low-voltage MR16 lamps. Traditional, halogen, low-voltage MR16 lamps are simple resistors and consistently dim well, with the right dimmer, regardless of whether they are fed from an ELV or MLV transformer. However, problems can occur when these lamps are replaced with LEDs (<a href='https://assets.lutron.com/a/documents/3683586_challenges_of_dimming_whi…; target='_self'>See Technical Paper, Challenges of Dimming LED Loads on ELV and MLV Transformers</a>).
Finding a dimmer, transformer, and LED lamp that are all compatible with one another can be difficult since the combination often results in lighting that flickers or buzzes loudly. Fortunately, many dimmable, LED MR16 lamps work off direct power (120/277V~) without the use of a separate, external, low-voltage transformer, and can be controlled using an LED-rated dimmer. 
 
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Recommended Options for Dimming LED MR16 Lamps
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Options for Best Performance
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<ul style='margin-top: 0in;margin-bottom: 0in;'><li style='margin: 0in 0in 0in 0px;line-height: normal;font-size: 16px;font-family: Aptos, sans-serif;'>Use an LED-rated dimmer</li></ul>
 
<ul style='margin-top: 0in;margin-bottom: 0in;'><li style='margin: 0in 0in 0in 0px;line-height: normal;font-size: 16px;font-family: Aptos, sans-serif;'>Replace the low-voltage transformer/LED combination with a dimmable, line-voltage, LED (not always possible; consult an electrician)</li></ul>
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If using an MLV transformer:
<ul style='margin-top: 0in;margin-bottom: 0in;'><li style='margin: 0in 0in 0in 0px;line-height: normal;font-size: 11pt;font-family: Aptos, sans-serif;'>Use an MLV-rated dimmer</li><li style='margin: 0in 0in 0in 0px;line-height: normal;font-size: 11pt;font-family: Aptos, sans-serif;'>Continue using halogen lamps instead of LED</li></ul>
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If using an ELV transformer:
<ul style='margin-top: 0in;margin-bottom: 0in;'><li style='margin: 0in 0in 0in 0px;line-height: normal;font-size: 11pt;font-family: Aptos, sans-serif;'>Use an ELV-rated dimmer</li><li style='margin: 0in 0in 0in 0px;line-height: normal;font-size: 11pt;font-family: Aptos, sans-serif;'>Continue using halogen lamps instead of LED</li></ul>
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Other Available Options
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If using an MLV transformer:
 
<ul style='margin-top: 0in;margin-bottom: 0in;'><li style='margin: 0in 0in 0in 0px;line-height: normal;font-size: 11pt;font-family: Aptos, sans-serif;'>Use an MLV-rated dimmer</li><li style='margin: 0in 0in 0in 0px;line-height: normal;font-size: 11pt;font-family: Aptos, sans-serif;'>Use a low-voltage LED* rated for forward-phase (leading-edge) dimming*</li></ul>
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If using an ELV transformer: 
 
<ul style='margin-top: 0in;margin-bottom: 0in;'><li style='margin: 0in 0in 0in 0px;line-height: normal;font-size: 11pt;font-family: Aptos, sans-serif;'>Use an ELV-rated dimmer</li><li style='margin: 0in 0in 0in 0px;line-height: normal;font-size: 11pt;font-family: Aptos, sans-serif;'>Use a low-voltage LED* rated for reverse-phase (trailing edge) dimming</li></ul>
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* Lutron suggests SORAA’s Vivid or Brilliant series of MR16, GU5.3 low-voltage LED bulbs. Visit soraa.com for more information. 
 
 
Verifying Minimum/Maximum Load Requirement
<ol style='margin-bottom: 0in;margin-top: 0px;'><li style='margin: 0in 0in 0in 0px;line-height: 107%;font-size: 16px;font-family: helvetica, arial, sans-serif;'>Verify that the transformer is rated to control LEDs</li><li style='margin: 0in 0in 0in 0px;line-height: 107%;font-size: 16px;font-family: helvetica, arial, sans-serif;'>Add up the LED wattage being controlled by EACH transformer – 
<ol style='list-style-type: lower-alpha;margin-bottom: 0in;margin-top: 0px;'><li style='margin: 0in 0in 0in 0px;line-height: 107%;font-size: 16px;font-family: helvetica, arial, sans-serif;'>Verify this is higher than each transformer’s minimum load requirement </li><li style='margin: 0in 0in 0in 0px;line-height: 107%;font-size: 16px;font-family: helvetica, arial, sans-serif;'>Verify this is lower than each transformer’s maximum output rating</li></ol>
</li><li style='margin: 0in 0in 0in 0px;line-height: 107%;font-size: 16px;font-family: helvetica, arial, sans-serif;'>Add up the “Input” rating of each transformer being controlled by the dimmer:
<ol style='list-style-type: lower-alpha;margin-bottom: 0in;margin-top: 0px;'><li style='margin: 0in 0in 0in 0px;line-height: 107%;font-size: 16px;font-family: helvetica, arial, sans-serif;'>For MLV Transformers – verify this is lower than the dimmer’s “MLV Transformer with Halogen” rating</li><li style='margin: 0in 0in 8pt 0px;line-height: 107%;font-size: 16px;font-family: helvetica, arial, sans-serif;'>For ELV Transformers – verify this is lower than the dimmer’s “ELV Transformer with Halogen” rating</li></ol>
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For Example:
 
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Equipment Ratings:
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Calculations:
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Maximum Dimmer Ratings: 
• LED: 250 W 
• MLV Transformer with Halogen: 400 VA 
• ELV Transformer with Halogen: 500 W
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Transformer (Minimum): 
• 20 W minimum transformer rating 
• 8 W LED rating 
• 20W / 8W = 2.5 – round up to 3 
• Minimum Transformer Rating: 3-LEDs per transformer
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Maximum Dimmer Ratings 
• LED-Rated; Electronic Low-Voltage 
• Input: 0.53 A Maximum • 
Output: 60 W Maximum; 20 W Minimum
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Transformer (Maximum): 
• 60W maximum transformer rating 
• 8W LED rating 
• 60W / 8W = 7.5 - round down to 7 
• Maximum Transformer Rating: 7-LEDs per transformer
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LED Ratings
• 8 W
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Dimmer (Maximum): 
• Transformer Type: Electronic Low-voltage • 500W maximum dimmer rating 
• 500W / 120V = 4.1-A maximum dimmer rating • 0.53 A Transformer Input Rating 
• 4.1 A / 0.53 A = 7.7 – round down to 7
• Maximum Dimmer Rating: 7-Transformers per Dimmer
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This article covers the challenges of dimming low-voltage LED MR16 lamps, different types of transformers, and choosing the appropriate Lutron dimmer.

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Dimming Low-Voltage LED MR16 Lamps

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