Bright Ideas

FAQ's - Under Cabinet LED Lighting

Posted by Geoffrey Walling on Jul 26, 2016 4:48:28 PM

We’re answering your most common questions regarding our Under Cabinet LED lighting.

The UCA series has been a popular fixture for RDA Lighting because it is multi-purpose and can be used in residential, commercial and industrial applications.  Not only does it brighten up kitchen spaces, but it can also light up PLC control panels as well as the insides of your boats or RV.  The possibilities are endless.

This blog post will cover the most frequently asked questions when it comes to installing and customizing our UCA LED under cabinet lighting.


KitchenBrickWall_149930441.jpgWhat are the limitations of a “run”? 

This has to be our #1 question.  What is a “run”?  It’s the maximum length of Under Cabinet LED strips recommended for use before you’ll notice a drop in voltage.  Some people believe that you can only do a two metre run off one power supply.  This isn’t the case.  With the original RDA UCA product, the standard maximum length of a run is about 32 watts in a series; this equates to approximately 80” of fixtures when using UCA or 120” on the UC product.

These lengths are guidelines; ask your licensed electrician to ensure they are accounting for voltage drops when using long runs of wire between fixtures.  You will experience a drop in voltage if the wire is coiled up between fixtures.  This is why you should always use the correct length of wire.  For your convenience, they are pre-packed as 6”, 40” or 80”. To get the exact length, use a DC cable connector with LVT or bell wire.

If you decide to add a splitter, you’ll be able to use two or three runs on one power supply. For example: when you are installing Under Cabinet Lighting with a 96 watt power supply, you could do two runs of two metres (32 watts) each.  In general, you want a power supply that has at least 10% more capacity than the calculated wattage, in order to account for potential voltage drops. For this scenario, you would use a splitter off the hardwired kit and have two leads going to the product.  Keep in mind you can still use a motion sensor with the splitter.


What are the voltage requirements of the UC, UCA, UCP, and UC series?

All fixtures use 24 volts DC as their input voltage, this can supplied by one of our plug in power supplies, dimmable or non-dimmable hardwire powers.  In industrial applications such as PLC or control panels, the 24V DC source can be supplied from other DC power supplies. In 12VDC automotive and boating applications, you will need to use a step up transformer to achieve 24VDC or you can special order 12V DC fixtures. 


What measurements should I keep in mind?

When installing your Under Cabinet Lighting, it’s important to allocate the correct amount of space for connectors and power feeds.  The basic rule of thumb is to allow an inch for each direct connector that you use and an inch and half to two inches for each accessory, including the PIR motion sensor, the DC junction box connector, or a touch dimmer.


What should I consider with color temperature?

Color temperature is one of the trickier aspects of lighting since it’s more about aesthetics, but also requires some knowledge of lighting principles to get it right.  When selecting a UCA you need to think about the color temperature in terms of the desired effect you want in the room.  This means accounting for the colors in the room.

For example, if the walls are white and you use a warm white UCA, it will look more yellow.  If you want to keep the color of your wall, then you would select a natural white UCA.  If you have a brown tile for your counter top, warm white might be the best choice.  Standard LED Under Cabinet Lighting units are offered in 3000 kelvin (warm white) and 4000 kelvin (natural white).

Think of warmer colors being earth tones like brown, green, and beige typically found in kitchens with natural wood cabinets and/or brown marble/stone counter tops.  These would typically be best suited for 3000k lights.

Kitchens with primary colors, stark white and stainless steel tend to appear brighter when cooler color 4000k lights are used.


What are my limitations with lighting controls? 

We receive many questions regarding how to correctly install motion sensors and dimmers with Under Cabinet Lighting.  There are a wide range of applications for motion sensors with UCA fixtures, including university cubicles, kid’s desks, work benches, inside a cupboard, crawl space, or panel box.

  • Will the motion sensor work if it is placed between two UCA strips?  No, only the fixture after the sensor will be controlled by the sensor.
  • Can I use a wall dimmer with a plug in power supply? No, line voltage (wall) dimmers can only be used with dimmable hardwired power supplies.  If you are using a plug in or non-dimmable power supply, you could use our touch dimmer to turn fixtures on/off and touch to dim up or down.

Why am I getting flickering?

Flickering can occur when you are using a line voltage dimmer and the line voltage dimmer is not recognizing the load.  Some electronic line voltage dimmers require a minimum 40 watt load.  For example, if you have a run with one 16W (40” section) this may be too small a load for the dimmer to control, and you may get flickering through the dimming cycle.  Most of the older (and cheaper) magnetic/incandescent dimmers will work very well even at very small loads of 3 watts.  Some of the new electronic dimmers have trim adjustments that allow the installer to find flicker points in the dimming cycle and use the adjustment to remove or reduce flicker. 

Please consult our customer service team if you are having trouble finding the right dimmer.


What’s the correct connection set-up?

When you want to create a long run (more than 80”) or if you need to fish wire behind drywall, you should use the DC junction box connector accessory with 18AWG 2 strand wire.  This wire is commonly known as 18-2 LVT (low voltage thermostat wire) or 18-2 Bell wire.  Always ensure the wire you use is properly certified for the application.

Using the DC junction box connector?  Make sure the negative and positive from the power supply are correctly connected to the negative and positive points of the connector.  Should you reverse them, the fixture will not light and you will need to start over and reconnect it.

Learn more about RDA’s Under Cabinet Lighting (UCA) series by clicking the button below.  If you have any questions that aren't covered here, please feel free to contact us


About the Author: Geoffrey Walling is a Lighting Specialist at RDA Lighting.  He fields questions daily about lighting layouts, installation, and fixture selection.

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Topics: Under cabinet lighting