Metal Halide & HPS Plant Grow Lighting Questions

NO. HID lighting requires a special ballast or transformer to ignite the bulb or lamp. The internal components of the ballast are designed to send the correct voltage and current for the rated lamp. Mixing bulbs and ballasts will result in premature failure and will void the manufacturers’ warranty. Consider the size area you want your garden to be prior to making a lighting purchase. It is better to grow into a fixture than out of one. It is important to always match your ballast and lamp wattage and type. For example, do not use a 400W HPS light bulb with a 1000W HPS ballast. This may fire up the lamp but could cause the lamp to explode or will reduce its life. Also you cannot run a metal halide bulb on a HPS ballast or vice versa. The only exception is that a 430W HPS bulb will run on a 400W HPS ballast (see #4). Also, special bulbs called conversion light bulbs can be used to convert an HPS ballast to MH or vice versa (see #5).

Yes, a 430 Watt HPS light bulb will run on a standard 400W HPS ballast (Ansi S51). However, you will only receive 400 watts of light output.

The "color" of light sources comes from a complicated relationship derived from a number of different measurements, including correlated color temperature (CCT) or Kelvin temperature (K), color rendering index (CRI), and spectral distribution (PAR Watts). However, color is most accurately described by a combination of Kelvin temperature and CRI.

• Color Rendering Index - CRI

CRI is a numeric indication of a lamp's ability to render individual colors accurately. The CRI value comes from a comparison of the lamp's spectral distribution to the standard (e.g. a black body or the daytime sky) at the same color temperature. The higher the CRI the more natural and vibrant the colors will look. A bulb with a CRI of 85 or higher is excellent being that the sun has a CRI of 100. Eye Hortilux makes 90 -92 CRI bulbs that are used in aquarium, horticulture and other applications such as the 400W Eye Hortilux Blue 90CRI and 1000W Eye Hortilux Blue 92CRI. Standard Metal Halide bulbs have a CRI of about 70, so only 70% of colors will be rendered correctly. HPS bulbs have a CRI of 22.

• What is the Color Temperature or "K" - Kelvin Rating?


The K rating is a generalized form of addressing the color output of a Light Bulb. Color Temperature is not how hot the lamp is. Color temperature is the relative whiteness of a piece of tungsten steel heated to that temperature in degrees Kelvin. HPS has a warm (red) color temperature of around 2700K as compared to MH at 4200K, which has a cool (blue) color temperature. The higher the kelvin temperature gets, the bluer. 10k lamps seem to be a nice crisp white, while higher kelvin can go from a blue/white to very blue and lower kelvin seem more like that of sunlight (6500k). Metal Halide bulbs go up to 20,000K (commonly used in aquariums) providing the bluest light.

• What is Spectral Energy Distribution & PAR Watts?

The total visible spectrum is perceived by us humans as white light, but the "white light" is actually separated into a spectrum of colors from violet to blue, to green, yellow, orange and red made up of different wavelengths. Plants use the blue to red part of the spectrum as their energy source for photosynthesis. The different combinations and the relative intensity of various wavelengths of light determines the CRI of a light source.

Only part of solar radiation is used by plants for photosynthesis. This active radiation Photo synthetically Active Radiation (PAR) contains the wavelengths between 400 and 700 nanometers and falls just within the visible spectrum (380 - 770nm). The light in this region is called PAR watts when measuring the total amount of energy emitted per second. PAR watts directly indicates how much light energy is available for plants to use in photosynthesis.

• What is the Lumen Measurement?

Lumen is a measurement of light output. It refers to the amount of light emitted by one candle that falls on one square foot of surface located at a distance of one foot from the candle. Traditionally, lumens have been the benchmark of a lamps ability to grow plants; meaning the brighter the lamp the better the plant. However, studies have shown that a broader color spectrum lamp will perform much better than a lamp with high lumen output, especially when it comes to plant growth.

Metal Halide and HPS grow light systems are perfectly safe to run in your home. All of our grow light systems are manufactured by Sunlight Supply and are UL listed. The UL listing indicates the grow light has been properly tested for safety.

Manufacturers do not indicate that gloves are required when handling MH or HPS Bulbs. However, it is recommended that your hands be thoroughly washed prior to handling these bulbs. However you should handle MH HQI double-ended bulbs very carefully and should wear gloves.

The inner arc tube of a Metal Halide lamp contains mercury. Underwriters Laboratory has stated that for a Metal Halide fixture to maintain its UL Listing, that an additional tempered safety lens is required in the event that the arc-tube and outer glass fail. This will prevent the spread of Mercury.

This depends on the type of plants and whether you have natural sunlight available to your garden. As a general rule, when you are in a vegetative stage of plant growth and you have no natural sunlight, run your lights 14-18 hours a day. If you have natural sunlight, it will vary because the sunlight may or may not be direct. It will take a little experimenting to find the best length of time to run your lights. If you are actively fruiting and flowering, the rule is to run your lights 12 hours a day if you have no natural light

HID (MH/HPS) bulbs should be replaced after 12 to 18 months of use. Although MH and HPS lamps will continue to light beyond 18 months of use, they will have lost up to 30 percent or more of their lumen output while consuming the same amount of electricity. The average life of a MH lamp is 12,000 hours for a 1000 watts lamp and 20,000 hours for a 400 watt lamp. The rated life hours for most HPS light bulbs is 24,000 hours. Most manufacturers rate their lamps by “Average Life Hours” and usually claim 10,000 to 24,000 hours. These ratings are based on when the lamp/bulb will completely fail to come on. They do not factor in loss of intensity or loss of color. MH and HPS light bulbs lose intensity and color through normal use. This is OK if you are lighting a warehouse, but when it comes to plant growth, these losses can mean wasted electricity and poor plant performance. Serious horticulturists recommend that replacing HPS or MH Light Bulbs after 6000 hours of use. This equates to using your light 16 hours a day for one year.

A Remote ballast kit is a system where the Ballast or transformer is a separate unit from the reflector. An enclosed Ballast light kit is a light system where the reflector and ballast are integrated in the same metal housing of these grow lights.

• Ballast
• Reflector with Socket & Cord
• Light Bulb

What is a Remote Ballast Grow Light Kit?

A Remote ballast kit is a system where the Ballast or transformer is a separate unit from the reflector. These ballasts are extremely heavy and some models are made to be wall mounted while others can simply be placed on the floor. Most of the items we sell are lighting systems (kits) for growing plants, herbs, seeds, and for greenhouses applications. Many of the items we offer are sold as Kits with many different options and components. A complete remote ballast grow light system would consist of a ballast, reflector, socket & cord and light bulb. The ballast (transformer) is needed to ignite the bulb. The reflector or hood is what is used to direct the light and usually has a reflective insert to provide greater light intensity. Many of the reflectors now come with the socket & cord pre-wired into the hood. The example to the left is item# 400HPSYLD1: 400W Sun System 1 Ballast with Yieldmaster 2 reflector and 400W HPS Bulb. So the components that would automatically be included in this system would be:

• 400 Watt HPS Sun System 1 Ballast
• Yieldmaster 2 Reflector with 6in. Fittings
• Standard 400W HPS Light Bulb. You have the option to upgrade your bulb. For more information on bulb upgrades go here.