Digital Ballasts – The Definitive Test from GroWell Hydroponics
Here is some magnetic vs. e-ballast testing data...
http://www.growell.co.uk/pr/57/Digital-Lights-The-Definitive-Test.html
Digital Ballasts – The Definitive Test
We’ve heard it all about digital ballasts – from ridiculous performance claims to unachievable physics, there seems no end to the fanciful claims of some manufacturers. The list of so called experts who have added their 2p to the digital ballasts debate seems to grow by the day, so in search of some definitive answers we have decided to carry out some tests.
Background
In order to understand our test results, you first need to fully understand the mechanics of how a ballast and lamp work.
High Intensity Lamps such as the Sodium and Metal Halide lamps that are used in grow lights need a ballast to regulate the power supplied to them. Without a ballast to control the power to the lamp, it would simply draw massive amounts of power and instantly fail. This is why you need to match your 600 Watt Lamp with a 600 Watt Ballast – so that the right level of power is supplied to the lamp and that the lamp itself is not damaged.
HID Lamps have a band of operation at which they will perform to their optimum level, the gases within the lamp will ignite correctly (providing the intended colour of light) and no unnecessary damage is caused to the lamp. In a 600 Watt Sodium Lamp for example, this range is from 580-660 Watts. Any further power to the lamp and you risk damage and the colour rendition from the lamp will not be as intended. You may achieve higher overall light output from lamps that are overrun above this safe level, but it will be expensive both in terms of electricity used and the need to replace your lamps more often. It is therefore very important to provide consistent power to your lamp within the safe range of operation for that lamp.
How traditional (magnetic) ballasts work
You may have heard a traditional ballast referred to as “magnetic” or “core and coil”. This is because a traditional ballast regulates power to your lamps by means of a coiled wire around a metal core. This creates a magnetic field (exactly like an electro magnet) which restricts the power allowed to reach the lamp. In very basic terms, the ballast is designed to balance against the pull of the lamp so that the correct level of power ends up being supplied. This method has worked very well for a very long time, but there are a number of flaws in the design.
To accurately regulate the power to the lamp, the ballast is designed on the assumption that the input power will always be constant. In reality this is not the case. Everyone knows that UK mains power is supposed to be 240 Volts, but in truth this can range from between 215-260 Volts depending on your geographic location, the time of day or even how many lights you have on the same circuit. What this means is that your traditional ballast (which is designed to provide 600 Watts to your lamp when it has a constant supply of 240 Volts) will actually supply varying levels of power to your lamp depending on the incoming supply. This is bad for the lamp (as it will degrade faster) and is also bad for your plants as they could be missing out on valuable light.
Another drawback of magnetic ballasts is that over time they will become less and less efficient and supplying the right power to your lamp. They will draw more power (costing you more on your bill) and will not correctly regulate the power to your lamp (meaning that you may have to replace you lamps more frequently).
How digital (electronic) ballasts work
The purpose of an electronic ballast is exactly the same as a traditional ballast – to regulate the power to the lamp. The way in which it does this is very different though. Rather than pulling against the draw of the lamp, an electronic ballast regulates the power supplied to the lamp via circuitboards and microprocessors. In practice what this means is that they supply exactly the desired power to the lamp (in the case of the Lumatek ballasts exactly 600 Watts to a 600 Watt Lamp). There is no loss of efficiency over time either – a 5 year old Lumatek will still supply exactly 600 Watts to the lamp just as a new unit would as it will not lose efficiency over time like a magnetic ballast will. This means that your lamps will always provide the correct colour and will last longer thanks to consistent supply well within its safe range of operation.
Electronic ballasts are extremely efficient. In our tests, the Lumatek ballast “lost” very little power between the wall and the lamp. The Watts of electricity drawn at the wall for a Lumatek 600 Watt ballast is 634 Watts – meaning that just 34 Watts are lost between the wall and the lamp. On our magnetic ballast tests, much more power was being consumed (especially with the older ballast) and the electricity bills associated with using these units would have been considerably higher than the equivalent electronic unit. Typically, a brand new magnetic ballast supplying the exact same 600 Watts to the lamp would “lose” between 50-60 Watts between the wall and lamp in the form of heat, noise and vibration. This amount of ”lost” power increases as the magnetic ballast ages.
Electronic ballasts also compensate for fluctuations in the supply – so unlike the magnetic ballast where light output can vary depending on the incoming voltage, the Lumatek will stay consistent no matter what happens with the supply. Your lamp output will always remain the same no matter what time of day or where in the country you use your light.
Increased Lamp Efficiency
Digital ballasts aren’t just more efficient at regulating the power to the lamp – Lumatek claim that they also operate your lamps in a more efficient way than a magnetic ballast and actually achieve a higher lumen output per watt.
A traditional magnetic ballast turns your lamp on and off 50-60 times per second whilst a digital ballast turns your lamp on and off approx 40,000 times per second. Lumatek claim that this high frequency lighting excites the gases in the lamp more efficiently and produces more Lumens per watt. At 50-60 times per second the amount of power the ballast provides the lamp (lamp power) is directly proportional to the amount of light it produces i.e one magnetic ballast providing 600w to the lamp will produce exactly the same light output as another that provides 600w lamp power. This is not the case with the lumatek ballast. For the same lamp power provided to the lamp the Lumatek increases efficiency by approx 5%. Combined with the better power management this gives efficiency gains by the Lumatek in the 10-20% range over magnetics (depending on voltage). At the time of writing, we have not been able to independently verify this additional lamp efficiency data, but given that all of their other claims have stood up to our tests with regard to power management then we have very little reason to doubt that this is also true.
To see all of our test results in an easy to read and easy to understand table by downloading our datasheet pdf here.
