Digital Ballasts vs. Magnetic Ballasts

Digital Ballasts vs. Magnetic Ballasts

Paul
Paul
04 Aug 2014

Using a magnetic ballast? It could be time to upgrade.

Magnetic ballasts may be cheaper to buy, but digital ballasts cost less overall.

Here’s why. 

What's a Ballast?

Each lighting system is made up of a reflector, grow lamp and a ballast.

It’s your ballast’s job to regulate how much power goes to your lamp:

Try using a grow lamp without a ballast and it won’t be pretty. If you’re lucky, your lamp won’t light. What’s more likely, is that your lamp will explode.

There are two kinds of ballast you can use - Magnetic & Digital.

Magnetic Ballasts

BAY6 Magnetic Ballast BAY6 Magnetic Ballast

These use what’s known as a ‘choke’ to regulate power output.

A choke is a steel core with a metal wire coiling around it.

  • The steel core is often laminated steel plates
  • The wire coil is often copper or aluminium

Together, the core and coil create an electromagnetic field that regulates the output voltage.

 

Digital Ballasts

BAY6 Digital Ballast BAY6 Digital Ballast


These use solid state circuitry to transform and regulate the power output to the lamp.

They’re much smaller, lighter and efficient than magnetic ballasts. 

In this day and age, most people are using them.

Which Ballast is Best?

The ballasts are very different. But which one's best? Digital all the way! Here's why.

1. Size and Weight

Ballast Ballast

This one's easy.

  • Magnetic Ballasts: Are big, bulky and heavy
  • Digital Ballasts (or electronic ballasts): Are small and light

If you're struggling for space, you'll find it easier to get a small, digital ballast in.

If you're mounting it with your reflector, as a complete fixture, digital ballasts are lighter, too.

2. Energy Saving

Ballast Ballast


Digital ballasts are waaaaay more efficient.

It’ll vary, depending on which units you compare, but typically digital ballasts use 3 - 4% less energy.

This doesn’t sound like much but, when you’ve got multiple grow lights on the go, the combined saving really cuts down your energy bills.

3. Heat Output

Heat output Heat output


Magnetic ballasts produce a lot more heat. The flow of electricity through the choke’s core and coil sees to that.

All of that heat is an unwanted by-product – evidence of how inefficient magnetic ballasts are.

Digital ballasts also generate a little heat, but not much compared to magnetic ballasts. Internal parts are actually sheathed in plastic to help prevent heat problems.

4. Noise

Ballast Ballast


The coils in magnetic ballasts vibrate, which creates a soft humming noise. This humming gets louder and louder as the ballasts age and the coils become looser. The loosening of coils also makes them slightly less efficient.

If you want to run a quiet grow room, always choose a digital ballast. They run silently, with no humming and no buzzing whatsoever!

5. Light Consistency

Light consistency Light consistency

Magnetic ballasts can only output the voltage that goes in – no more, no less.

This is a BIG problem, because the output from a standard UK mains electrical supply ranges from 220-258V, depending on your location.

Magnetic ballasts operate well at 230-240V...

  • Lower than this and they’ll underperform
  • Higher than this and they’ll use more energy

To complicate matters further, voltage from your mains supply can fluctuate by 10- 15V depending on:

  • The time of day (due to the demand on the grid)
  • The amount of electricity you are drawing on a circuit at your property

Every time you add an extra magnetic ballast to the electrical circuit that powers your grow room, the voltage reduces. This decreases the light output of all your lights!

A variation in the mains voltage means a variation in electrical consumption and light output. Ultimately, this can harm plant growth and lower your yield.

You won’t get any of this with a digital ballast. They have the ability to transform the incoming voltage up or down, regardless of the supply.

 

6. Frequency of Lighting

Ballast Ballast

Magnetic ballasts are governed by the frequency it gets from the main supply (around 50Hz).

Basically, this means it’ll go on and off 50 times per second. That’s a fairly low frequency that creates a ‘flickering’ sensation. Digital cameras actually capture the banding effect it creates.

Digital ballasts regulate the output frequency. You’re looking at a frequency of 40,000-100,000 Hz, depending on the brand and model.

This excites the gases in the lamp more efficiently. Overall you’ll have a better light output, a longer lamp life and more accurate colour rendering.

7. Dimmable Lighting

Ballast Ballast

Digital ballasts can be dimmed. Magnetic ballasts can’t.

Why dim lights? 

1. In early veg, plants are still very delicate. A light that’s too intense can stress and shock them. To prevent this, start off on a dim setting then slowly increase your intensity to ease plants in.

2. To control your temperature you can lower your light intensity. This'll happen automatically if you have a GAVITA or Dimlux controller.

 

8 Overdrive function

Lighting Lighting

With a dimmable digital ballast, you can overdrive your output by 10%. This means you can give your plants the extra push they need for bigger yields.

Example: 

A 600W lamp can emit 660W for a short period of time. Doing this does reduce your lamps life so use sparingly.

Caution: 

Don’t ever overdrive a Metal Halide lamp – they won’t be able to take the output.

9. Economics

Ballast Ballast

Magnetic ballasts are cheaper to buy, but cost way more to run and are slightly quicker to degrae.

For optimum efficiency, you should replace your magnetic ballast every 2-3 years.

Digital ballasts last much longer, and have a consistent output over their life. They only need replacing if they stop working, which can be 10+ years.

When you break it down, and take running costs into account, it costs less to run a digital ballast.

10: Digital vs. 400V

Ballast Ballast

The icing on the cake with digital ballasts 400V lighting.

400V ballasts take 230-240V (delivered by the mains electrical supply in your house) and transform it up to 400V. Why? It’s all about the lamps.

The short of it is: 400V lamps produce more plant usable light (micromoles) than standard 230V lamps (more on micromoles here).

The average increase with 400V lamps is 8% more light, which produces better growth and on average 10% higher yields compared to 230V!

Summary

Which ballast should you use? It’s a no-brainer really – digital ballasts all the way!

Benefits of a Magnetic Ballast:

  • Cheaper to buy

Benefits of a Digital Ballasts:

  • Cheaper to run (uses less electricity)
  • Lightweight and compact
  • Cooler
  • Silent
  • Consistent, high light output
  • Dimmable
  • Overdrive function – intensify your lights
  • Longer life

Just for good measures, here's a comparison table

  Magnetic Digital Digital 400V
Initial cost Low Medium High
Running cost High Low Low
Efficency Low High High
Noise High Low Low
Heat High Medium Low
Size and Weight High Low Low
Life span Low Medium High
Dimmable No Yes Yes
Controllable No No Yes
Light Output Medium High Very High

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Paul
Paul
About the author

Paul is our Merton shop manager. If you haven't met him yet, he's as friendly as they get. 

GroWell Hydroponics Merton

Call GroWell Merton:
020 8648 6327