The Kele LDIM2 and Fluorescent Dimming

The Kele Model LDIM2 is a dimming control for 0-10V dimmable fluorescent/LED lighting ballasts. It is an excellent interface between a building automation system (BAS) and the dimming ballasts. However, it’s important to understand the workings of the ballast system when designing controls around the LDIM2. The key to understanding this 0-10V ballast dimming system is in the fact that the 0-10V signal originates in the ballast, not in the LDIM2.

The LDIM2 sinks this 0-10V signal and drags it down to the level specified by the input, thus dimming the lights. It also provides feedback on both setpoint and output via 4-20 mA signals. According to the IEC 60929 standard, any output of 10V or above means 100 percent (full) lighting, and any signal of 1V or below signifies minimum lighting for that particular ballast (may be anywhere from OFF to 40 percent light output).

A question we are frequently asked at Kele is, “How many fluorescent or LED ballasts can the LDIM2 support?” The answer is that it depends on the output limits of the particular fluorescent or LED ballasts to be dimmed. Some, for example, comply with IEC Standard 60929 and are limited to 2 mA output on the 0-10V signal. Since the LDIM2’s output is rated at 0.5A, it can drive (0.5A/2mA) or 250 ballasts of this type. Some ballasts are rated a bit higher (non-compliant), and some a bit lower, so it’s important to know the ballast output current limit in order to calculate the number that can be connected to a single LDIM2.

The LDIM2 also features a wide range of input signals: 0-10V, 2-10V, and pulse width modulation from a digital BAS output (adjustable, 0.1 to 25.6 seconds). The dimmable range is typically 40 percent to 100 percent for a typical 0-10V dimmable ballast. In addition to feedback from both setpoint and output, the LDIM2 features manual override settings of 40, 50, 60, 70, 80, 90, and 100 percent. In the event of input signal loss, the output can be set to go to 100 percent level, or to maintain the current brightness level (dip switch selectable).

There are also ballasts (primarily found in theatrical stage lighting) that expect the controller to source the 0-10V signal. These ballasts are specified to conform with standard ESTA E1.3, Entertainment Technology – Lighting Control System– 0-10V Analog Control Protocol. If you run into this type of ballast for fluorescent or LED systems, your controller must source the 0-10V signal, and you’ll still need to obtain the current requirements for the ballasts in question to determine how many you can control with a single 0-10V signal from your BAS.

In either case, the 0-10V signal is most often designated as Class 2, per the National Electrical Code. Thus, it’s important to separate the signal wires from the power wires to the LED or fluorescent fixture. Another important note is that ballast replacement must be made with the same make and model as the ballast to be replaced. Doing this maintains the fixture’s UL listing, and also allows for equal dimming of adjacent fixtures. Different ballasts may have different dimming profiles.

Contact Kele with questions about the LDIM2 and your dimming control needs.

2 thoughts on “The Kele LDIM2 and Fluorescent Dimming

  1. Hi

    We have installed LDIM2 PCB’s in our lighting control panels, we are using them to dim multiple 0-10v LED lights, we have set dip switches 1 and 7 on.
    When we bench tested them with a small powered dimming module the output worked fine. but now the control panels are connected to the BMS 0-10v they don’t work, can you please help us to solve this, maybe a diagram showing the connections from a BMS control system

  2. The current LDIM2s work with 24VAC or 24VDC so both types of input power can use the same common. There is only one Common on the BAS side for power and signals in/out. Please note our published diagram concerning your 0-10V BAS input. Has 24V power been verified? Has 0-10V BAS signal at the input terminals been verified? Please also try using the Manual Override options using the dipswitches to verify that output side is working with the ballasts properly. If not, we would recommend trying that next. Would show whether the problem is on BAS side or lighting side.

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