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HOME + GROW INFORMATION + GROW LIGHTS FAQ

FAQ: GROW LIGHTS

What light is right for me?
What type of light is better, High Pressure Sodium or Metal Halide?
Why do people use Metal Halides or High Pressure Sodiums?
Is there a light, for under $200, that you could recommend?
What type of light system would be best for someone with a limited grow space?
I have a large room, how many lights do I need?
Can I grow a tomato plantr full term under one of the newer high intensity fluorescents ?
I grew (4) 48" fluorescent bulbs. My plants were pale and spindly. Is my light level too low?
Questions about Bulbs:
What is the difference between 120 volt and 240 volt?
What is the difference between lumens and wattage?
What is the difference between High Pressure Sodium and Metal Halide?
Can I interchange bulbs between lighting systems?
What are Conversion Bulbs?
Are there lights/ballasts which can burn both Metal Halides and High Pressure Sodium bulbs?
What size light should I purchase?
What is the life cycle of Metal Halide and High Pressure Sodium lamps?
What precautions should I take with HID lights/ballasts?
Is it true that HID lamps can explode?
My bulb flickers when I turn it on. Is this normal?
How long do I have to leave my light off before I can turn it on again?
What is the difference between the Tek and New wave units?
Can a T5 fluorescent light fit in to a regular fluorescent light fixture?
Can the HID bulbs you sell plug into a regular socket?

Questions About Light Setup:
How do I hang my lighting system?
I have an area that is lit by normal fluorescent lighting.Can I use T5 bulbs in their place?
How much area can a 400 watt HID lighting system cover? Would a light mover help?
What does the Light Cool Kit do for my lights and how does it work?
What fan would you recommend for the DayStar AC Reflector with 6 inch flanges?
I recently purchased a Vortex fan, CAN 9000 Filter and Flange. How do I connect the flange to the filter? Which way should air flow to exhaust heat out?
 

What type of light is better, High Pressure Sodium or Metal Halide?
There are several things to consider when picking the right light for your gardening needs.

First, do you have any natural light available, and if so what type? When supplementing natural sunlight, use a High Pressure Sodium bulb to extend daylight in the early spring and fall. You can also use them on cloudy, low-light days. When no natural light is available at all, a Metal Halide bulb is most frequently used, which is a very wide spectrum bulb perfect for indoor growing. Halide lights are excellent for vegetative growth of leafy plants like lettuce and basil.

A second factor is bulb efficiency and life expectancy. Sodium bulbs are superior to halide bulbs in terms of efficiency: they put out more light per watt and last approximately twice as long. Of course, halide lights provide much better spectral distribution, so ultimately, the decision about which is best comes down to what's most important to you.

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Why do people use a Metal Halide for vegetative growth and High Pressure Sodium for flowering?
There are a couple of reasons growers switch between bulbs during different stages of plant growth. First, sodium bulbs can make some plants grow "leggy" and stretched out due to the high yellow to red spectrum they give off. Halide bulbs tend to keep plants "tighter", with less space between internodes. Consequently, some people use metal halide lights during vegetative growth to keep the structural growth of the plant nice and tight, but switch to sodium bulbs during the flowering stage when plants need more light. Although sodium bulbs don't have as balanced a spectrum as halide bulbs, the intense light they put off does promote flower and fruit development. Bottom line: switching bulbs is a matter of personal preference.

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Is there a light, for under $200, that you could recommend for growing fruits and vegetables in a basement year round?
We recommend either the Sun System V HPS 400w or the Sun System X HPS with EconoWing Reflector

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What type of light system that comes wired to plug in to a standard home outlet would be best for someone with limited grow space for indoor plants?
Most of our lighting systems are wired to plug in to a standard 120V outlet. You can special order a system for a 240V outlet (the type of outlet you plug a washing machine into). There’s a ballast kit that you can screw a fluorescent light into which runs around $110. However we highly recommend that you spend a little more money and get an all-in-one HID light kit. The kit comes with the reflector, an HPS 400w light bulb, a socket, and ballast. This ballast and bulb kit will plug directly in to a standard wall outlet. Take a look at our selection of Mini Grow Lights

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I have a large room. How many lights do I need?
We've created a Lighting Calculator to help you figure out the correct number of lights for your room. It will tell you the wattage per square foot of various lighting configurations of your choosing. Play with it to decide what sort of lighting arrangement you'll need.

For optimum lumens, you'll need between 20 (minimum) and 60 (maximum) watts per square foot. There may be several different arrangements that will give you the optimum light energy. For example if you needed 2400 watt, you could fill that with (2) 1000 watt lights and a 400 or with (4) 600 watt lights, etc.

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Can I grow tomatoes or peppers full term under one of the newer high intensity lamps such as the New Wave or Teklight?
The 48" T5 bulbs are reported to be about 5,000 lumens per bulb. So an eight light model is somewhere in the range of a 40,000 lumens. That is just barely enough to grow only one tomato per fixture. If you want to grow more then one plant, it is probably better to go with an HID light. You may do a bit better with peppers, but they really vary in what they need. You might be able to grow a few plants under an eight light model, depending on the variety. For a point of reference, in a sunny summer location, Mother Nature will flood every square foot of garden space with 75,000-100,000 lumens of perfectly balanced sunlight.

  • A 400 watt HPS bulb is somewhere around 45,000-55,000 lumens
  • A 600 watt HPS bulb is somewhere around 85,000- 95,000 lumens
  • A 1000 watt HPS bulb is about 100,000 lumens.
> What the T5 Fixtures are good for is vegetating plants. They are very similar to Metal Halide bulbs in their ability. You can grow beautiful herbs and lettuces under them. Also some orchids do well under them. They are great for starting a batch of tomatoes under and having some really nice size plants to set under an HID light or outside for flowering or fruiting

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I tried to grow tomatoes under four 48" fluorescent bulbs rated at 1900 lumens. My plants were pale and spindly. Is my light level too low? What kind of light do you suggest? I used FloraFro, FloraBloom, & FloraMicro fertilizers and followed directions. What am I doing wrong?
Your plant light levels are WAY too low to grow any kind of fruiting or flowering plants. Fluorescents are great for early plant stages-you can vegetate a plant under them and do all right, but you will completely fail for blooming (as you unfortunately learned). If you think about it tomatoes grow in full sun in the summer time (see previous question for further information). These fluorescent lights aren't putting out anywhere near that kind of energy. What you need is an HID light. We suggest a 400 watt HPS Light.

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What is the difference between 120 volt and 240 volt?
Both 120 volt and 240 volt lights operate with the same 100% output and use the same amount of electricity. A 600 watt light uses the same amount of current in 120 volt as in a 240 volt light. The standard outlet you see in your house is 120 volt.

You may want to get a 240 volt if you plan on running several lights off of one circuit breaker. The maximum wattage on a 120 volt circuit is 1500 watts, per the National Electric Code. With the proper breakers or fuses and wire, 240 volt circuits can carry up to 5760 watts. This means that you can plug several high powered lights into a lighting timer that will turn them all on and off on the same circuit. 240 volt is also considered to be more 'stable' because it uses half the amounts of amps. The equation goes like this Amps x Volts = Watts.

Installing a 240 volt outlet is considered 'basic' electrical wiring and it can be done on your own with the correct tools and with a good home electric book. Warning! Electricity is very dangerous and wiring on your own should not be attempted unless it is done so seriously and carefully. If you don't know what you are doing then contact a professional!

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What is the difference between lumens and wattage?
Lumens refer to the total number of light particles coming from the bulb. Wattage refers to the amount of electric power, expressed in watts or kilowatts which a bulb uses. In other words, lumens describe bulb brightness while wattage describes the power usage.

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What is the difference between High Pressure Sodium and Metal Halide?
Although high pressure sodium and metal halide are both types of HID (High Intensity Discharge) lights, they emit different color spectrums. High pressure sodium bulbs emit very bright light that is concentrated in the red to yellow side of the spectrum and weak in the blue-violet end. Metal halide bulbs, by contrast, emit a very balanced light, which contains all the energy peaks of the visible spectrum. Both types of lighting have their place in an indoor growing environment.

Another difference is the lumens per watt of both bulbs. (Lumens is the measurement for the efficiency of the bulb or how much light you're producing for the amount of electricity you're using). Sodium bulbs produce between 97 and 150 lumens per watt. Halide lights produce 65-115 lumens per watt. An easy way to tell difference between the two types is by appearance. Sodium bulbs appear very yellow-orange; halide bulbs appear more blue-white.

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Can I use different bulbs in my system?
No. Never interchange bulbs between systems unless they are specifically designed to do so. Lots of people ask if they can use a 1000 watt bulb in a 400 system and the answer is NEVER! It's dangerous; the bulb could become unstable and explode. You should also never put halide bulbs in a high pressure sodium system or high pressure sodium bulbs in a metal halide system. The ballasts are only meant to run the type of bulb they are rated for. If you want to interchange bulbs between systems get a conversion bulb; a high pressure sodium bulb designed to run off a halide ballast, and vice versa. But remember -- only use the bulb in a system it is designed for.

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What are Conversion Bulbs? How do they work?
Conversion bulbs are designed to allow metal halide systems to produce high pressure sodium light (MH-HPS) and high pressure sodium systems to produce metal halide light (HPS-MH) . This type of bulb allows you to tailor the light source to the growth stage of the plant (again, using halide blue light for growth and sodium red light for flowering/budding) merely by changing bulbs.

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Are there ballasts which can burn both MH and HPS bulbs?
Yes. .Our favorite option is to purchase a Digital Ballast, which, in addition to being able to run MH or HPS, will also save energy and produce more lumens.

The alternative is to purchase a regular magnetic coil ballast with a switch. Most of the lighting systems we sell on this site can be upgraded to switchable options.

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What size light should I purchase?
It depends on your space and electrical requirements. First, figure out what square footage you'll be working with. But don't just figure for the whole room. Figure out what the plant area is that you need to cover. Multiply length x width to get square footage. You'll need at least 30 watts per square foot. For example: if you have a 4 x 4 area, which equals 16 square feet, multiplied by 30 watts you get 480 watts. That means you need at least a 430 watt light. Keep in mind, the actual amount of light you'll need depends on how much light the type of plants you are growing like. Some plants like more light, some like less.

For more help, check out our Lighting Calculator

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What is the life cycle of Metal Halide and High Pressure Sodium lamps?
Metal halide lamps should be changed at least every 6 to 12 months if you're burning them 18 hours per day. High pressure sodium bulbs, burned at 12 hours per day, will last between 6 months and a year and a half depending on the bulb.

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What precautions should I take with HID lighting systems?
A little care should be taken to ensure the safety of your HID lighting system. Remote ballasts should be placed safely out of the way where they can not be knocked over or splashed with water. Ideally they should be off the floor to allow for better cooling and to prevent problems in the case of flooding. Ballasts can get very warm and should not be placed near anything flammable.

Always be sure that the outlet the lamp is plugged into is rated for the amount of electricity you are using. Pulling too much electricity through wiring that's too small can cause electrical fires. We suggest putting all lighting systems on GFCI outlets. You have probably seen these kinds of outlets - they have a small red 'reset button on them. They can prevent electrical fires.

A GFCI is not dependent of a ground to function. It does not measure shorts to the ground, it measures the current difference between the hot and neutral wires. A sudden difference of 5 ma. or more, indicating that there is another path for the electricity to flow through will trip this device. It protects any appliance plugged into it, and can also be wired to protect other outlets that are connected to it.

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Is it true that HID bulbs can explode?
HID bulbs can explode if they are not handled correctly. This will occur if the bulb is very cold when first turned on, or if there are fingerprint oils or moisture on its surface. To prevent accidents, never pick the bulb up directly by the glass. Handle the bulb by the base and wrap the glass body in a paper towel. Handling the bulb through the paper towel, screw it carefully into the lamp body.

If you need to clean the bulb, use a towel lightly dampened with window glass cleaner or rubbing alcohol; wipe all fingerprints, dust and impurities from bulb's glass surface. Let dry thoroughly before installing. After cleaning, always handle the glass through a paper towel. Also, make sure bulb is warmed up to room temperature before installing.

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My bulb flickers when I turn it on. Is this normal?
It usually takes about 30 seconds for a bulb to ignite, and it can take up to 5 minutes for it to reach full brightness. As the lamp brightens, it will probably flicker and change color for several minutes. This is totally normal and is nothing to worry about.

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How long do I have to leave my lighting system off before I can turn it on again?
When MH bulbs are turned off they should be left to cool for 20 minutes before re-starting. Turning a Metal Halide bulb on when it is already hot severely shortens the life of the bulb and it can affect the intensity of the light. Metal Halides should be replaced after a year of heavy use.

High Pressure Sodium bulbs can be restarted after only 2 or 3 minutes after being turned off, and they should be replaced every two to three years.

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What is the difference between Teklight and New Wave units?
Both units have the same lumens/watt. The difference is in the quality of workmanship and materials. The TekLight is sleek, black, and very nice looking. The New Wave is more of a shop light. Both lights come with a two year warranty. In the end it comes down to aesthetics

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Can a T5 fluorescent light fit in to a standard fluorescent light fixture?
Unfortunately nothing that you would be able to pick up at a local hardware store would work with the T5. The T5 bulbs fit into their own unique Fixture.

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Can the HID bulbs you sell plug in to a regular socket?
The Grolux like all other HID (metal halide or high pressure sodium) do not plug into regular sockets. They need to plug into a "mogul" base socket which will connect to (and be charged by) an HID ballast (in the case of Grolux, a 600W HPS ballast ). The ballast is equipped with the requisite transformer, capacitor, and igniter, which are all you need to fire up the bulb.

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How do I hang my lighting system?
Installing the fixture and reflector is very easy. We sell a Light Hanging Kit that comes with all the parts you need. This kit allows the raising and lowering of a grow light reflector in one easy movement.

As an alternative to hanging the light from your ceiling, you can purchase a light stand.

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I'm attempting to convert a 24' x 36' building with one window at each end into an indoor greenhouse. Right now it is lit by normal fluorescent lighting. I am wondering if the bulbs can be changed out using T5 bulbs in their place.
You can use tubes such as AgroSun Fluorescents. They are about 20% brighter then standard fluorescents. As for the T5 bulbs, they need specialized fixtures, such as the New Wave or the Teklight.

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How much area can a 400 watt HID lighting system cover? And how much improvement would putting it on a mover offer?
A 400w HID covers a 3x3 area very well; anything beyond that will be less than adequate. If you were to put it on a mover and cover a 6x3 area it would illuminate as if it were a 200w light. This is fine, but not great for vegetation. You don't want to do this in bloom because it will result in stretchy, leggy plants with small fruits and flowers. We suggest considering a 600w or 1000w if you are going to use a light mover and cover a 4x6 or 4x8 area. A 600w covers a 3.5-4ft x 3.5-4ft area in “full sun”. A thousand watt covers a 4-4.5 ft area in “full sun”.

For more help in choosing lights, check out our Lighting Calculator

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What does the Light Cool Kit do for my lights and how does it work?
An Air cool Kit will reduce your heat by about 3-7 degrees. The kit includes vent flanges and a cover which you attach to the sides of the reflector. By including a fan and some ducting you can remove some of the heat from the light. The Air Cool Kits are reflector specific. Please contact us if you need help finding the right one for your reflector.

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What fan would you recommend for an the Daystar AC Reflector with 6 inch flanges?
You can cool the DayStar AC Reflector with an Active Air vent fan. While you can use the 265 cfm, the 465 cfm model will serve you much better. However an inline fan like the Vortex is really the way to go. Along with being better for continuous use (12-18 hours a day) they are also much quieter and more efficient when running through ducting since they have no 90 degree turns. The Active Air fans take in air at a 90 degree angle, perpendicular to the side that they push the air out of. This is fine if there is no ducting, but once you connect ducting to the Active Air your cfms are cut almost in half because of that 90 degree angle. The DayStar AC system was made to be cooled with a 6 inch fan.

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I recently purchased a Vortex fan, CAN 9000 Filter and Flange. How do I connect the flange to the filter? Which way should air flow to exhaust heat out?
The Flange comes with double sided tape.  You apply the tape to the flange and then peel of the tape on the other side and press it onto the filter.  Then you use the self tapping screws that also came with the unit and drill them into the top of the flange (through the flange) and into the top of the filter. These screws need a second to "catch"; but once they do they will go through the remaining metal on both the flange and filter rather easily.

Here is a simple diagram for Exhausting the room with one filter and fan:
http://www.igrowhydro.com/InfoSheets/Diagram-AirCool_NoCO2_SmallHut_EasiestStyle.pdf
Here is an example of Exhausting the Room and Air-Cooling the Light all with one Fan and Filter:
http://www.igrowhydro.com/InfoSheets/Diagram-AirCool_NoCO2_SmallHut.pdf
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