A sodium vapor lamp is one of the most frequently used grow lamps when it comes to growing in your own four walls. The term Sodium vapor lamp (HPS) * is also wrongly used for otherMetal halide lamps (MHLs) *. used.
With this post we want to provide a clarity and address the advantages and disadvantages concerning this types of light systems.
The best MHL grow light for the growth phase
The best HPS grow light for the flowering phase
MHL / HPS complete sets for beginners
Sets have the great advantage that all parts are coordinated with one another, they are delivered pre-wired and are slightly cheaper than the individual parts, if bought seperatly.
We therefore recommend this complete grow lamp set especially for beginners.
Our pre-calculated HPS & MHL grow light dimensioning
If you don’t want to buy an MHL / HPS complete set * , you need these accessories for your grow lamp.
MHL & HPS always require a ballast for operation – it must be adapted to the power (watt) of your lamps. The GIB is an electronic ballast, the advantage here is that the life of your lamps is extended. However, it costs a little more.
Execution from 250W-1000W.
The cheap alternative to the electronic ballast is the analog one, with the disadvantage that it also requires more power than the electronic alternative. You can choose from 150W to 1000W.
The number of watts must be adapted to your lamps
The pre-wired reflector is connected directly to the ballast. Again, you should pay attention to the wattage of your lamps and buy the right reflector.
Don’t want to switch the light on and off manually in your grow lamp? Get yourself a timer.
Electronic ones are suitable for low power, but from around 400W you should use an analog one. This can handle the current peaks better.
For the very cautious, we recommend a relay with a timer from 1000W, so that you are better protected against possible cable fires or the like.
Which grow lamp / how many watts for my grow tent ?
As mentioned above, this depends very much on the size of your tent.
For the growth phase you should have at least 30,000 lumens per m2, for the flowering phase at least 50,000.
In our article on lighting systems , we describe how to calculate whether a lamp is powerful enough for your grow tent . The best thing to do is to read through the part about light intensity, or you can choose your lamps from our precalculated table.
What you should know about gas discharge lamps
HDLs and MHLs belong to the gas discharge lamps- like your ordinary neon tubes. They consist of a cathode and an anode, which are located in a sealed glass bulb. This is filled with gas. If a certain voltage is applied, a gas discharge occurs and light is generated.
If you are interested in how exactly it works, you can read the Wikipedia article on gas discharge lamps. For us as growers there is really only one thing that is interesting to know. While MHLs must be operated with exactly the power for which they are designed (e.g. 400W), sodium vapor lamps can be operated with a variable power.
Electronic / digital ballasts * consist of circuit boards and computer chips, get less warm and have almost no loss and are therefore better at generating the voltage required for the lamp. Not only do you get more out of the lamp, older lamps that have lost a little of their power over time also shine with an electronic ballast.
Okay, back to the variable power sodium lamps. Of course, that doesn’t mean that a 400W HPS can be operated with a 250W or 600W ballast. There are, however, electronic laminated ballasts that can provide up to 10% additional power via a switch. So 400W suddenly becomes 440W or 600W becomes 660W.
But that only works with HPSs. MHLs must be operated with the performance for which they are designed. Otherwise they’ll break.
Advantages of the gas discharge lamp
Now we come to the advantages of gas discharge lamps. The first and most important argument would be the emission of monochromatic light . This means that the light only depicts a tiny area of the entire light spectrum.
We can make use of this property because we know exactly which spectrum our protégés need in the growth phase and which in the flowering phase . This is good because the light from other spectra can hardly or not at all be used by the plants.
Next you have to say that HPS and MHLs are very bright (approx. 150 lumens per watt). With the same power you will get less light intensity with conventional fluorescent tubes (approx. 45-100 lumens per watt). A 250W sodium vapor lamp has 33,000 to 40,000 lumens, depending on the manufacturer.
The last point to be mentioned is that the lamps are very cheap . That’s because they are used almost everywhere in the world. You have probably seen thousands too, because they are often used in street lights.
These are the disadvantages of the gas discharge lamp
But gas discharge lamps also have disadvantages. On the one hand, they generate a lot of heat . They get quite hot when in use and are also a bit more sensitive to dirt. You should not touch them with greasy hands, otherwise there is a risk that the residues will burst them during operation.
Plus, they still use quite a lot of electricity . For a 100 × 100 cm area, you should use at least a 400W lamp. There are now alternative light sources such as LEDs , which are a bit more energy efficient but also more expensive to buy.