HPS and MH lighting - Tips and info, optimal distance from tops!

Discussion in 'Indoor Lighting' started by THContent, Jun 8, 2010.

  1. THContent

    THContent Banned

    This is basically like a mini guide and crash course on HPS and MH lighting, benefits of each, differences to other types of lighting, and most importantly knowing the proper distance between the bulbs and your plants - regardless of heat!

    Some basic things to know, what is MH/HPS?:

    - MH: Metal Halide
    - HPS: High Pressure Sodium

    MH and HPS are far superior lighting alternatives to the sun over any other type of lighting known to man. Some people suggest that you should accommodate lighting relative to your space, I disagree. You CAN use up to 1000W MH/HPS system in a closet as long as you have a method to carry the heat from the bulb to the outside of the house, not back in to the room! For this I recommend getting a cooltube on ebay for about $100, or building one yourself as my signature will show you everything to do that, which will roughly be $35 for everything, minus the ballast. And then combined with a 160CFM inline fan, and some ducting and tape, you are on your way to a balanced temperature closet grow using 1000W HPS/MH! Please keep in mind I am not responsible for you burning your house down from lack of experience or knowledge, common sense plays a big part in this. It is critical that the plants have a hygrometer right next to the plant to monitor temperature and humidity, temp should be between 75-79 degrees F, this is when optimal photosynthesis production occurs. Regardless of what people say about the hand test method to test the heat from the bulb, this is a misconception! With MH/HPS systems you should be careful as to not get too close to the plants with the light, even if it feels cool, I have a couple of graphs below that illustrate acceptable distances from the bulb for best growth/lumens/PAR. If you get too close (regardless of heat), your plants can in fact get too much light by being too close, this will cause a plant's top to get white and feel rubbery to the touch. Too far away and you lose lumens and light output to plant, so the graphs below are to illustrate how you can maximize distance while maintaining optimal temperature.

    Combined with the proper nutrition, environment, and proper care, your flowering and budding will exceed that of any other artificial lighting used. You will yield higher with MH/HPS, there is no dispute, so long as the conditions are met for this plant to thrive!

    Always keep your temps in the grow room between: 68 and 85 degrees to avoid stress to your plants. However plants are fine for short periods of time a little above or a little below this range.

    MH/Metal Halide:

    Metal halide lamps, a member of the high-intensity discharge (HID) family of lamps, produce high light output for their size, making them a compact, powerful, and efficient light source. By adding rare earth metal salts to the mercury vapor lamp, improved luminous efficacy and light color is obtained. Originally created in the late 1960s for industrial use, metal halide lamps are now available in numerous sizes and configurations for commercial and residential applications.

    Like most HID lamps, metal halide lamps operate under high pressure and temperature, and require special fixtures as well as ballast to operate safely.

    Since the lamp is small compared to a fluorescent or incandescent lamp of the same light level, relatively small reflective luminaires can be used to direct the light for different applications (flood lighting outdoors, or lighting for warehouses or industrial buildings).

    HPS/High Pressure Sodium:

    High-pressure sodium (HPS) lamps are smaller and contain additional elements such as mercury, and produce a dark pink glow when first struck, and a pinkish orange light when warmed. Some bulbs also briefly produce a pure to bluish white light in between. This is probably from the mercury glowing before the sodium is completely warmed. The sodium D-line is the main source of light from the HPS lamp, and it is extremely pressure broadened by the high sodium pressures in the lamp; due to this broadening and the emissions from mercury, colors of objects under these lamps can be distinguished. This leads them to be used in areas where good color rendering is important, or desired. Thus, its new model name SON is the variant for "sun" (a name used primarily in Europe and the UK). HPS Lamps are favored by indoor gardeners for general growing because of the wide color-temperature spectrum produced and the relatively efficient cost of running the lights.

    High pressure sodium lamps are quite efficient—about 100 lm/W—when measured for photopic lighting conditions. They have been widely used for outdoor lighting such as streetlights and security lighting. Understanding the change in human color vision sensitivity from photopic to mesopic and scotopic is essential for proper planning when designing lighting for roads.

    Because of the extremely high chemical activity of the high pressure sodium arc, the arc tube is typically made of translucent aluminium oxide. This construction led General Electric to use the tradename "Lucalox" for their line of high-pressure sodium lamps.

    Xenon at a low pressure is used as a "starter gas" in the HPS lamp. It has the lowest thermal conductivity and lowest ionization potential of all the non-radioactive noble gases. As a noble gas, it does not interfere with the chemical reactions occurring in the operating lamp. The low thermal conductivity minimizes thermal losses in the lamp while in the operating state, and the low ionization potential causes the breakdown voltage of the gas to be relatively low in the cold state, which allows the lamp to be easily started.

    At the end of life, high-pressure sodium lamps exhibit a phenomenon known as cycling, which is caused by a loss of sodium in the arc. Sodium is a highly reactive element, and is easily lost by reacting with the arc tube made of aluminum oxide and the products are sodium oxide and aluminum:

    6 Na + Al2O3 → 3 Na2O + 2 Al

    As a result, these lamps can be started at a relatively low voltage but as they heat up during operation, the internal gas pressure within the arc tube rises and more and more voltage is required to maintain the arc discharge. As a lamp gets older, the maintaining voltage for the arc eventually rises to exceed the maximum voltage output by the electrical ballast. As the lamp heats to this point, the arc fails and the lamp goes out. Eventually, with the arc extinguished, the lamp cools down again, the gas pressure in the arc tube is reduced, and the ballast can once again cause the arc to strike. The effect of this is that the lamp glows for a while and then goes out, repeatedly. That is how you know it is time to get a new HPS bulb.

    More sophisticated ballast designs detect cycling and give up attempting to start the lamp after a few cycles. If power is removed and reapplied, the ballast will make a new series of startup attempts.

    LPS lamp failure does not result in cycling; rather, the lamp will simply not strike or will maintain its dull red glow exhibited during the start up phase.

    About MH and HPS:

    Both MH and HPS systems are far more efficient than other artificial light sources. MH and HPS work far better than other artificial lighting sources because they produce a spectrum closest to that of natural sunlight. MH should be used during vegetative growth due to that of the summer sun, which emits more of a blue spectrum of light. HPS lighting should be used during flowering/bloom period due to that of the fall sun, it emits more of a orange/red spectrum of light which triggers the flowering when combined with reduced lighting (12 on/12 off).

    Some basic things to know:


    How far should my lights be from my plant's you ask?

    MH graph for optimal bulb placement from plants:

    HPS graph for optimal bulb placement from plants:

    MH Percentage of sun power, graph:

    HPS Percentage of sun power, graph:

    Enjoy! And nothing ever beats the SUN!!!
    Last edited: Jun 8, 2010
    • Like Like x 7
  2. GetThisOrDie

    GetThisOrDie Registered+

    Wow very informative post! Great links and charts! Sticky!

    Rep up for ya for posting alot of info to help people.

    Cant wait for the die hard LEDers to read your post lol!
  3. THContent

    THContent Banned

    lol, yeah haha I myself got a couple led panels but saving those for a later grow.
  4. THContent

    THContent Banned

    Is there any staff left on these boards at all? If so, when do they get around to reading posts... lol.
  5. drudown11

    drudown11 Registered+

    im really intrigued by LED lighting, but I will never pay 450 dollars for a 150 watt fixture, and i will never spend 400 dollars on a 90 watt fixture.

    I could get 2 1000 Watt HPS lights for the same price, and grow 3 times the bud.
  6. Psycho4Bud

    Psycho4Bud The Modfather

    Definately worthy of a sticky.....GREAT POST!

    Have a good one!:thumbsup:
  7. THContent

    THContent Banned

    Thanks Psycho, you are the one mod I have come to respect as of yet :D


    I will see about adding some more useful info in time :)
  8. THContent

    THContent Banned

    Good points.
  9. Hbuddy

    Hbuddy Registered+

    Im working with 400 watt and 1000 watt dual balast set ups. I was wondering which light i should be using for veg. and which for flower?
  10. lbrends

    lbrends Registered

    400w metal halide for veg and the 1000w high pressure sodium for flower will be the way to go.
    • Like Like x 1
  11. n00b

    n00b Registered+

    Gotta 400w MH for veg and 400w HPS for flowering. Just picked these up recently. Hoping my second grow will surpass my first by leaps and bounds given this. This is great reading, however, I moved my MH closer to my new batch of seedlings (about 2.5 weeks old) as recommended in the attached chart and think that I got them a little crispy. Are these the distances recommended for plants once they are out of the seedling stage? If so, what are the recommendations for distance for a new seedling crop or should I not even bother with the MH until they are out of the seedling stage?
  12. KnowledgeIsPower

    KnowledgeIsPower Registered+

    What would happen if you put a 400watt HPS bulb into a socket that was connected to a 400watt MH ballast? Beuler? Anyone?
  13. pipesdaddy

    pipesdaddy Registered+

    Such a great post. It's really difficult to believe that anything is left. Such a great piece of information.
  14. THContent

    THContent Banned

    I appreciate everyones interest in my mini guides :D

    I am not trying to stir up a bees nest but I just wanna add something here.

    If you notice, alot of the people that boast about their LED grows being better than MH/HPS belong in nuthouses. Not only that but they are usually the people that are promoting them in order to sell them. They will show you pictures of their LED grows showing crazy buds... But you will also notice they let their plants veg for alot longer than normal... MH/HPS closely replicates the same output as the sun which is what plants have known since the beginning of time, for someone to come along and say that plants only use certain light waves is false. If you had to compare for example, someone that is selling vitamin D out of the bottle in pill form for them to say it is better than vitamin D from the sun. See where I am going with this.

    Not knocking LED's but cmon guys be real here. ALL experienced growers know that HPS/MH is the single best unsurpassed alternative light source to the sun. If I was selling something, I would only be pointing out the benefits of something too... Kinda like cigarette companies.

    Bottom line: Side by Side MH/HPS beats LED hands down to grow plants.
    Last edited: Mar 29, 2012
    • Like Like x 2
  15. eatingglass

    eatingglass Registered

    HPS is not the solar spectrum. MH is closer to the sun. With this, there are several types of MH.
    In theory, plants should grow better with MH because of the spectrum, and in fact grow better with HPS.
    For lighting streets often selected LPS lamps, which have even higher performance - lumens / watt.
    Probably like a lot of red hemp waves and so HPS is better. However, it is found HPS lamp, which has a high rate uMol.
  16. THContent

    THContent Banned

    Anybody that is thinking about purchasing a lighting system, stick to MH Hands Down! LED's have proven to be a new aged ripoff they side by side will never equate in any way to HPS or MH lighting. If heating is your concern spend the money you would have spent on some overpriced LED's and build a cooltube, just read my grow log and tutorials for a cooltube and if your not satisfied then I would say waste your money on the LED setup but remember in the end the LED marketers are gonna take u for a ride and your buds will be pop or sized, they over hype them and grow with MH then put LED's up and take pics and say hey, look at my LED results.... The are just promoting it to make money regardless of hour yield so take it from me someone with actual knowledge and results that are not bs or tampered with and go the route that has ALWAYS proven to beat everything except the sun itself, MH or HPS combined with a cooltube and you won't be sorry I will wait for the thanks :)
    • Like Like x 2
  17. THContent

    THContent Banned

    MH graph for optimal bulb placement from plants:

  18. THContent

    THContent Banned

    HPS graph for optimal bulb placement from plants:

  19. whitewallgrower

    whitewallgrower Registered+

    1407440460459.jpg hi im a first time grower. Im using 2 2 40w flourecent 40" lights. The lights don't put off any heat so I have the plants about 1-3 inches from the lights at all times. Just wondering if I should do anything different. They are all healthy and full of leaves 1407440720500.jpg 1407440720500.jpg 1407440720500.jpg 1407440720500.jpg the 2 plants are in 10qt buckets. The other 7 are in buckets according to their size 1407440866092.jpg just wondering if everything looks good. 1407440955782.jpg

    Attached Files:

    • Like Like x 1
  20. 710Dabmaster710

    710Dabmaster710 Registered

    Not true anymore LED
    Are the way to grow..

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