Mark Lewin from Zano Controls introduces a solution for successfully dimming low loads.
It can seem like LED dimming is never straightforward. We all know that TRIAC dimming methods tend to be incompatible with LED loads, but the issue of load compatibility doesn’t end there; even digital LED-specific dimmers can fail to sufficiently dim certain loads. Somewhat surprisingly, the biggest stumbling block for installers seems to be dimming low, rather than high, loads.
TRIAC dimmers
Firstly, TRIAC or ‘leading edge’ dimmers tend to have a high minimum load, as they were originally designed with resistive loads – as used by traditional Incandescent bulbs – in mind. As such, many TRIAC dimmers simply won’t cooperate at all with a low-wattage LED installation. 
Secondly, leading edge dimmers operate a current interruption method that reduces power to the light source in order to dim the level of light emitted. Unlike incandescent bulbs, LEDs run on a continuous forward current, which can result in those current disruptions becoming visible in the LED’s light output. It can also cause the coil within the mechanism to buzz at lower levels, as it struggles to facilitate the low load.
Paired with a decent number of LED lamps, a leading edge dimmer may be able to achieve an acceptable light output when dimmed within a comfortable, mid-level range but, as the dimming level drops, that current interruption becomes more apparent, resulting in flicker and buzz.
Digital dimmers
Even with a digital ‘trailing edge’ dimmer, created specifically for LED drivers, an under loaded circuit can bring its own set of problems, including flicker, dropout or a failure to work altogether.
Many digital dimmers available in stores can dim between 10-300W. While this is a suitable range for some basic domestic LED installations, it can become problematic when a low load is required.
Take an LED installation in an en-suite bathroom, a study, or even a reading nook, that requires just two downlights. Each lamp consumes 4.5W each. A minimum 10W controller won’t support that low level.
Even if the combined wattage of an installation is compatible at full power – for instance, four 4.5W LED lamps on a 10-300W dimmer, set to full capacity – the installation can still fail to achieve the lower lighting levels desired, as the dimmed load fails to reach the 10W minimum level preset required by the driver. This can result in the lamp dropping out when dimmed below 10W, or flickering as the driver struggles to maintain a consistently low current to power the fitting.
Problem solved
It’s a problem that Zano Controls’ Technical Support team have encountered frequently, as frustrated installers search for a way to achieve low level dimming on low loaded circuits. Luckily, Zano’s award-winning ZLED technology can provide a solution.
The ZGRIDLED 5-250W can support loads as low as 5W, making it perfect for small space circuits, or secondary circuits that require just a few lamps on one dimmer. It’s compatible with both leading and trailing edge technology, fits eight leading grid systems and is not limited to 10 lamps per circuit, eliminating some of the other frustrations caused by LED dimmers.
“The ZGRIDLED 5-250W can support loads as low as 5W, making it perfect for small space circuits, or secondary circuits that require just a few lamps on one dimmer.”
Even more versatile is the ZBARLED range, which starts at 0W and can support up to 1000W on one circuit. Also compatible with both leading and trailing edge systems, the ZBARLED can be used to control a mix of LED and incandescent bulbs on one circuit, with the 0-1000W model enabling the product to adapt to a variety of low and high loads.
Testing
Just as it is important to test large loads prior to installing dimmable LEDs, it’s crucial to test low loaded circuits to ensure that the installation can achieve as wide a dimming spectrum as possible once fitted. Zano Control’s Technical Support team test ZBAR and ZGRID products against a range of lamps from leading manufacturers, and are happy to test any lamp on request.
