LED Dimming Guide Part 3: Checking Compatibility

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June 1, 2016

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Compatibility is by far the most important element when choosing LED dimming options, whether that is between a lamp and a driver, a lamp and a dimmer or even all three.

This article covers LEDs and older dimmers, matching an LED with new dimming systems, and dimmer loads – how many LEDs you can put on one dimmer.

It is part of a series of articles on LED dimming and uses some terms which may be unfamiliar to you so we recommend you read ‘Things to consider when dimming LED’ first. ‘Methods of Dimming’ will explain some of the terms used.

Our LED Jargon Buster and LED FAQs complement this article. Check these if you are unsure about terminology.

Older dimming systems

People often assume that their new LEDs with work seamlessly with their dimming switch as it has become second nature to buy a replacement lamp and have everything work perfectly.

Unfortunately, there are no guarantees that your new LEDs will work with your old dimmer. At some point, almost all technology gets overtaken and replaced.

Your new LED might work on your old dimmer, it might not. The only way to be certain is to buy one and try it out. However, before you do that check out our ‘Considerations when dimming LED’ for more information on using old dimmers with new LEDs.

LED and modern dimming systems

Modern dimming systems are very varied and come with a lot of hoops to jump through to make sure your system works. Essentially, you follow a path which varies depending on where you start and what choices you make.

You may also want to view our LEDs and Drivers Guide and our Dimming Methods introduction to better understand what each option is.

Dimming and Electrical Loads

An electrical load is the amount of power drawn by appliances on a circuit. For example, you have a circuit from the positive end of a battery, to a torch light, then back to the negative end of the battery. If the torch light requires 1W of power, then the load on this example circuit is 1W.

Maximum load

Dimmers have a maximum load they can sustain. If a dimmer has a maximum range of 400W, it is critical you do not place more than a 400W load on this dimmer.

For example, 10 x 60W incandescent lamps all wired to one 400W dimmer would seriously risk damaging both the dimmer and the lamps.

With incandescent lighting, ensuring you didn’t overload the dimmer was easy enough. If the dimmer was 400W maximum you could put up to 6 x 60W incandescent lamps. 6 x 60W = 360W. Whereas 7 x 60W = 420W is too much.

LEDs complicate this equation. It isn’t so simple as to say I have a 400W dimmer so I can dim 40 x 10W LEDs.

Due to a phenomenon known as in-rush, for a short period of time an LED operates at a much higher wattage than its average. A more in-depth explanation of this can be found in our ‘Things to consider when dimming LED’ article.

You should aim to load a dimmer with LEDs to only 10% of its maximum wattage, and you should never load a dimmer with LEDs to more than 25% of its maximum.

Minimum load

As LEDs are comparably very efficient, they have a very small average wattage. This means you need to select a dimmer with a low, ideally zero, minimum wattage.

Older dimmers would have a minimum wattage of somewhere between 30W to 50W. This is because the dimmer was designed to steal some of the power from a lamp on the same circuit.

This causes a problem for LEDs as they are low wattage and will behave erratically or will not work at all on these dimmers. For example, a 10W LED will not perform properly with a dimmer that has a minimum load of 50W.

Modern dimmers overcome this problem by incorporating a neutral wire which allows a dimmer to have a minimum wattage ranging from 0W to 10W. This means you can expect an LED to perform well on a modern dimmer.

A more in-depth explanation of this can be found in our ‘Things to consider when dimming LED’ article.

So, the practical implication of this is that you should aim to buy a dimmer with a minimum load of 0W for perfect dimming, or at most a minimum of 10W.

Dimming Guide part 1: Things to consider when dimming LED

Dimming Guide part 2: Methods of dimming LED

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