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Do cmh run hotter than hps of the same wattage?

Discussion in 'Lighting' started by SpliffShady25, Dec 7, 2017.

  1. I'm about to buy my lights I have 8ft hight in my basement and will be running ebb and flow so take 3ft away for the res n the table with small plants. I was planning to go wit 4 1000 hps which I heard the light takes up about a foot and you gotta give about a foot of space between the lamp and canopy so that's another 2 feet which leaves me 3foot growing space. I was thinking maybe I can get the 630 cmh's n cover the same amount of space and get closer to the canopy but I read somewhere the cmh gives off more heat than hps per watt. Is this true and can the cmhs cover the space and have the penetration of the four one thousands I ask cuz I may eventually lose the tables and go for big plants. Thanks for any replys.

    Sent from my iPhone using Grasscity Forum
  2. if heat is a problem for your area, then you can check out the LED grow light.will be cooler,save your cooling bill also
  3. Appreciate your reply but I just don't have the money or time to get into leds yet maybe after a few crops. For now I'm looking for my best cheapest option to get started. My main concern wasn't heat it was hight limitations and how close I can get to the canopy. Since with hps I'll be losing about 5 or 6 feet to the set up and having two to three feet of actual vertical grow space. I might just go with aircooled 1000s since they are cheap and you can get the canopy pretty close to the light.

    Sent from my iPhone using Grasscity Forum
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  4. HPS will not cost you too much, but you need to change it every 3-4 month. and it release more heat, LED grow light,with specific spectrum which plants need,and release less heat, in long term ship , it will save your bill.
    We have a new series Mars ECO, you can check out.

    You can start with HPS, later you can think about LED.
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  5. Cmh run a lot cooler than hps. You can get closer to the canopy.
  6. I've looked into this very question and while some would argue with me, it seems the facts are this...

    In a perfectly sealed environment... any light source whether its LED, CFL, HPS or CMH will produce the exact same heat load to a closed and sealed environment if using the same wattage... this is physics...

    So a 400w HPS, 40x 10w leds, 10x 40w CFL's will all add the same amount of heat to a closed environment....

    Now the point where people want to argue this is dealing with efficiency... most people would say "well light X is more efficient, therefore it produces less heat" which is actually incorrect. Light turns to heat when it strikes a surface... therefore if you look at wattage like this wattage in = waste heat produced + light converted to heat you will see that regarless of efficiency. All the light in a closed room will turn to heat.. therefore the total wattage being used determines the heat load... 1w = 3.41 BTU

    The only factor which may play into this, is that we don't all grow in perfectly sealed (isolated) rooms so many times things like HPS lights may run actually cooler than a LED light (at the same wattage) being that the HPS light many times will be placed in an air cooled hood which evacuates some of the heat before it reaches the tent or grow environment, where a LED light at equal wattage blows ALL of the warm air into the grow area... so the LED would actually heat the grow area more (at equal wattage).

    Now the claim that LED's run cooler (as Sara had mentioned above) is only sort of true... LED's are more efficient at producing light than HPS bulbs... so it takes slightly less electricity/wattage to generate the same amount of light... For instance lets say that LED's put out 20% more light... So if you compared a 1000w HPS to a 800W LED, they would be putting out the same amount of light (hypothetically for this example), therefore you are using 200w LESS of energy, which in this case you are running 20% cooler because you are running 20% less wattage. Its not that the technology itself is cooler, its that its more efficient at producing light, therefore, less wattage equals less heat load... if you compared at 1000w HPS with a 1000w LED though, the heat load would be the same.

    Now in regards to using 630 CMH vs 1000w HPS... I would recommend CMH all the way.... the spectrum is about as close as you can get to sunlight currently (other than plasma) which is very inefficient, but CMH is actually one of the most efficient light sources for producing PAR light currently (other than some quantum boards and low powered LED arrays such as COBs). I highly recommend either going CMH or looking into LED quantum DIY boards.
  7. No. What you are neglecting in all your reasoning is light spectrum. Infrared in particular. HPS puts out far more infrared then the other light systems you're talking about. The newest leds are capable of covering the same areas as hps with a little more then half the wattage.

    The minor advantage that hps and some CMH lights have is vented hoods. They are much better at eliminating heat then high end leds which are essentially the same thing as an open hood.

    Comparing HPS and leds at the exact same wattage is not a fair comparison either. The led is going to put out the same umol or ppf at about 60% as much watts. If you compare them at the same wattage you'll have way more actual light in the led room. Comparing the heat output at the same ppf or par light output level would be the most fair. If you do that the led puts out less then half the heat because of being more efficient at turning electricity into light compared to an arc light and having a more ideal light spectrum with less infrared.

    I do agree that if you want intense bloom lights you're going to have heat to eliminate no matter what light system you use. I think HPS is more of a challenge significantly then the other options. It's also partially because it takes more watts of hps to fill an area. Any successful HPS grower will tell you that you want about 50 to maybe 60 watts per square foot for flower. With high end led that figure is as low as 30 watts per square foot. That can't help but make way less heat.
    • Agree Agree x 1
  8. Actually my reasoning is correct... You misunderstood what question I was answering...I answered the OP's question. which was...

    "I read somewhere the cmh gives off more heat than hps per watt. Is this true."

    the answer is NO...

    Less wattage equals less heat...

    Equal wattage = Equal heat load.

    I answered it perfectly.
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  9. Explain to me then why my 630 watt light can be on for 24 hours with no air cooling and be cool to the touch. It’s a sealed glass hood unit. Both ballasts which produce heat are also inside hood. Now my remote ballast 600 watt HPS will melt your skin if you touch the hood with no air on after about an hour of running. That’s a easy thing to notice if you have both.

    Smotlys Top Shelf Seeds.
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  10. You also are not taking into account spectrum like Tbone mentioned. Infrared rays create more heat than Ultraviolet. Hence lack of UV heat lamps keeping stuff warm. Now another factor is the gas compounds in the bulbs. Traditional bulbs burn gas at near plasma state at different temps based on compounds in the arc tube. Some gasses give off more heat than light when burning. So there are more variables than a simple watt to heat conversion.

    Smotlys Top Shelf Seeds.
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  11. One of my coworkers caught his chair on fire with a 20 watt inspection bulb from 8 inches away. It was a GE sunnex bulb. When you replace it you have to wait several minutes to change it or it will melt through your latex gloves and skin. Learned that the hard way.

    Smotlys Top Shelf Seeds.
  12. I can tell a difference when I swap out my HPS bulbs for MH finishing 10,000 k spectrum too. There is virtually no infrared to be converted into heat. The plants actually use most of the higher energy short wavelengths (UV) produced instead of converting to heat on canopy.

    Smotlys Top Shelf Seeds.
  13. This is just not true. I agree that you will still have considerable heat no matter the light system. It won't be nill with led or CMH but to say it's the same watt for watt? You said it yourself in your first post. In your example you said that the led is maybe 20% more efficient at making light from electricity. You underestimated quite a bit. It's more like 50%-100%. A 550 watt led fixture can make as much light as a 1000 watt hps but you can put your hand on the led after it's been running all day.

    I have 250 watts worth of leds in my veg tent. You can put your hand on them and the drivers. My wall mount drivers run at 98 degrees. The lights themselves are maybe 110 degrees with no fans or heatsinks. You just cannot do that with HPS or CMH. Try putting your hand on a 250 watt open hood hps light that's been on for hours.

    CMH lights are also more efficient at making light from electricity. They have a better spectrum so lack much infrared that helps cause excess heat. That's why most of them don't even have vented hoods. Just try putting a gull wing 600 watt hps in a tent without a vented hood. Good luck. Many people are running the 630 cmh lights with open hoods though in tents.
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  14. Your missing the facts...

    Light turns into heat when it hits a surface...

    If you put 1000 watts in to a light... lets say its 50% efficient...
    500w of waste heat are formed instantly, and 500w of Light Energy is emitted. What happens when those 500w of Light energy are absorbed... it creates HEAT :) therefore no energy is lost.... it only changes forms

    If you do the same example, with a 60% efficient light... same thing... 40% waste heat is formed, 60% light energy is formed... the 600w of light energy turns into heat..... so 100% of 1000w turns into heat

    When you have a light on in a dark room, and flip the light switch, what happens? The room goes dark right?

    Why is this......?

    Because the light that was producing photons of light stopped producing the photons when you turned it off. All of the photons in the room became absorbed, and this absorption creates the atoms in each surface to vibrate at higher levels, causing friction which creates heat.... which is released into the room.

    Of course you can touch the front of an LED, because they way they disperse heat is through the back... you wouldnt' want to touch the back of an LED while its on... you would burn the crap out of your hands... They heat they put out is dispersed differently.... which is why they required heat sinks and generally have fans cooling them....

    1W = 3.41 BTU/hour... as you can see, this formula has no "efficiency" or spectum in it.. this is the power unit describing the Rate that electric energy converts to heat energy....

    The first law of thermodynamics, also known as Law of Conservation of Energy, states that energy can neither be created nor destroyed; energy can only be transferred or changed from one form to another.

    Anyhow... believe what you want...this IS the correct answer...
  15. Define what light is? Light is not light. There are an infinite amount of ways to make a light spectrum. Ever hear of a heat lamp? What spectrum are those? Infrared. What spectrum does HPS have more of infrared.

    Because of this optimal room temps with led are actually 4-5 degrees warmer then when running HPS. The established optimal room temp after decades of indoor growing is about 78 with HPS. This is because with the infrared and other "wasted" areas of the spectrum where HPS is stacked it impacts surface leaf temps much more then led and other forms of light that have a different spectral makeup. Optimal room temp for these lights is more like 82. That's what I run when I can.

    If light was light then HPS would not impact surface leaf temps more then led.

    I could go touch the back of my leds right now. They are about the same temp as the front since my led lights are about 3-4mm thick.
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  16. [​IMG]
    My heating pad for my back is hotter.
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  17. I would run 2 315 cmh over a 600watt HPS any day. I run just one in veg open hood and I can rest my hand on the hood for as long as I want. The only cooling I do in the summer is open the top 2 vents in my tent and one bottom one with a fan pulling in cooler air.
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  18. Just to add to the conversation; ceramic metal halide light produce more UVB and infrared than any other grow light except a LED dedicated to that spectrum.

    This is one of the biggest benefits over all other light sources. Unfortunately I you use a CMH in a cool tube, or a fixture that is not open; you are filtering out those benefits. A 315 CMD compares to at least a 600 HID; some say its closer to 700 watts of HID. It also has a PAR rating of 90-92 versus 25 for sodium and 60 for my.

    LEDs just happened to develop at about the same time as CMH, and took the spotlight. Which is great, 3500k cobs are almost equivalent to CMH spectrums; and eat less juice. But they still lack UVB and infrared spectrums.

    Sodium's and MH are obsolete compared to CMH and LEDs. CMH would of been the wave if not for LED. CMH still have their benefits.

    If your budget allows for 4000 watts of power, I would alternate 400 watt LEDs and 315 watt CMDs. Whatever LED that can match the footprint of the CMH. Just so you can treat the light the same.
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  19. I think CMH has been around for a very long time just never utilized in the growing arena. I just saw that Hortilux just released their CMH HPS bulbs as well. I like the fuller spectrum over intense red tho. and a few companies are now making 1000watt DE CMH bulbs which I'm sure kick ass!
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