Cobs Suck !!

Redeyes82 said:

You’re lost off in some other shit. Why are his cobs constantly burning out? What’s your take. Why can’t he turn them all the way up? What are your thoughts? I’m saying malfunction. You’re going on about things that I’m not even talking about

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I don't know why his cobs are burning out, I would never suggest cobs myself. He likely can't turn them up all the way due to a driver mismatch or something. It is true that cobs are less efficient than more modern led boards, in that you need more wattage to produce the same amount of light (same with hps), so I guess from that perspective I could understand how someone might think they were hotter.

Redeyes82 said:

No you won’t

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I used to think what you think. Science proved me wrong. Then I still didn't want to believe it so I did my own tests. Try for yourself.. Turn off all fans in a tent (no ventilation) then turn on a 600w hps for an hour, and record the temp. Let the tent cool down and do the same test with an led fixture at identical wattage. You will discover that the tent temps are identical regardless of the type of light. Sorry, but you're quite wrong on this.

PJ Diaz said:

I don't know why his cobs are burning out, I would never suggest cobs myself. He likely can't turn them up all the way due to a driver mismatch or something. It is true that cobs are less efficient than more modern led boards, in that you need more wattage to produce the same amount of light (same with hps), so I guess from that perspective I could understand how someone might think they were hotter.

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You’re right about heat production according to the literature. I’ve never read up much on it. Seems to me the hps is much hotter in same space and heats it up faster but perhaps that’s just me imagining things

Redeyes82 said:

You’re right about heat production according to the literature. I’ve never read up much on it. Seems to me the hps is much hotter in same space and heats it up faster but perhaps that’s just me imagining things

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It's because you are feeling the radiant heat produced by the lamp. Put a thermometer at the top of the tent (heat rises), and you will appreciate the heat produced by a LED fixture equally to that of HPS.

It is true that you need only around 75% of the LED wattage (assume it's a quality fixture) vs that of a HPS fixture to get the same light output, so from that perspective you do produce less heat for the same amount of light, but it's because you are consuming less watts. watts to btus is directly proportional.

I had 100ww cobs i mounted on huge heat sinks then put a fan on top of that. They lasted about three years but only cost about $10 ea. Heat is the enemy of a LED. I got some cheap 12" 80ww strip lights with reflector and no heat sink at all on them. You could cook off the reflector if you wanted to. I mounted a fan on it and all is well, so far. Just started using them.

Forgive me I may be wrong but is it the amount of electricity that turned in to light and not heat. The efficiency of the light out to power draw?

Fishbulb said:

Forgive me I may be wrong but is it the amount of electricity that turned in to light and not heat. The efficiency of the light out to power draw?

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The lighting industry needs some sort of standard. Currently advertising watts in too many formats. One is actual power draw and should be the only thing mentioned. Any other watt rating or label is compared to what? One thing I notice is it is usually a 10X the actual power draw that they get labeled. Same with all the light measuring standards as to being too many used.

So you need a light meter and and amp meter.

I have three kinds of lights currently in my flower room and another I'm using for the first time in the Veg tent.. At 12" here is what they put out for LUX. I picked 12" due to my phone light meter maxing out at 32k Lux.

at approximately 12" and in Lux

150W HPS 30k/150w=200 Lux per watt
80W FS strip 10k/80w=125 Lux per watt
60W LED array 30k/60w=480 Lux per watt!!!!
50W FS LED COB 7k/50w=140 Lux per watt

HPS puts out a lot more heat

Three Berries said:

The lighting industry needs some sort of standard.

HPS puts out a lot more heat

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They do follow the same standards set by physics and thermodynamics. Total draw and heat will stay the same no matter what light you use at the same draw. Advertisment will always fool stupid people without own judgement.

Like other mentioned new growers think HID's are much hotter because they can physically feel the IR radiation coming from the bulb, that doesn't mean they heat a room faster than a LED fixture does at the same draw.

The industry doesn't need a new standard, people need to better educate themselves by reading and understanding basic specs and physics.

Wastei said:

people need to better educate themselves by reading and understanding basic specs and physics

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There is a thing called efficiency - how much power drawn from power supply becomes waves of certain wave length and how much becomes heat. LEDs are more efficient, which means more power from supply becomes light and less becomes heat. HPS' less efficient, which means less power becomes light and more becomes heat. Also HPS' are more on the red side of the spectrum, which means more IR waves are emitted.
So, yes, basic physics says that with same draw LEDs heat spaces less then HPS.

Cappuchino said:

There is a thing called efficiency - how much power drawn from power supply becomes waves of certain wave length and how much becomes heat. LEDs are more efficient, which means more power from supply becomes light and less becomes heat. HPS' less efficient, which means less power becomes light and more becomes heat. Also HPS' are more on the red side of the spectrum, which means more IR waves are emitted.
So, yes, basic physics says that with same draw LEDs heat spaces less then HPS.

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I'm sorry but efficiency has nothing to do with total heat emitted if the draw is the same. What's lost through the driver/ballast plays a part but you can't change physical law and thermodynamics to be honest.

It may differ if you put the driver outside of the grow room. Most people use a "lung room" though so heating will in most situations still be identical.

However if you run a LED fixture at 480w it will emit as much usable light as a comparable 600w HPS bulb. But then the draw is not identical and 480w emits less heat than 600w, that's pretty self explanatory.

Wastei said:

They do follow the same standards set by physics and thermodynamics. Total draw and heat will stay the same no matter what light you use at the same draw. Advertisment will always fool stupid people without own judgement.

Like other mentioned new growers think HID's are much hotter because they can physically feel the IR radiation coming from the bulb, that doesn't mean they heat a room faster than a LED fixture does at the same draw.

The industry doesn't need a new standard, people need to better educate themselves by reading and understanding basic specs and physics.

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No right now watts are used in lighting by manufactures like is is in audio. I just bought a 1000w LED that draws 110ww or so they say. What does the 1000w refer too? 1000 watts of HID?

Cappuchino said:

So, yes, basic physics says that with same draw LEDs heat spaces less then HPS.

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Show me where basic physics says that? All basic physics I've seen clearly show that 1watt = 3.412btu's no matter the fixture is. Science bro, not bro-science.

Three Berries said:

No right now watts are used in lighting by manufactures like is is in audio. I just bought a 1000w LED that draws 110ww or so they say. What does the 1000w refer too? 1000 watts of HID?

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You are talking about fraudulent lighting companies though. Show me one legit company who does that.

Three Berries said:

No right now watts are used in lighting by manufactures like is is in audio. I just bought a 1000w LED that draws 110ww or so they say. What does the 1000w refer too? 1000 watts of HID?

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Usually that means that incandescent bulb of the same brightness will draw 1000W.

PJ Diaz said:

Show me where basic physics says that? All basic physics I've seen clearly show that 1watt = 3.412btu's no matter the fixture is. Science bro, not bro-science.

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For example: https://pllight.com/how-led-and-hps-lighting-can-affect-air-and-leaf-temperature/
As I said above

Cappuchino said:

Also HPS' are more on the red side of the spectrum, which means more IR waves are emitted.

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Cappuchino said:

For example: https://pllight.com/how-led-and-hps-lighting-can-affect-air-and-leaf-temperature/
As I said above

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Thank you for proving my point. You said that "So, yes, basic physics says that with same draw LEDs heat spaces less then HPS.". The article you posted confirms that it doesn't, and clearly says "A single watt of power is equal to 3.41 BTUs so a 600W luminaire will produce 2,046 BTUs. This is true for both the LED and the HPS luminaires." The article is talking about the difference in leaf temp vs air temp under different light sources, which while related, is an entirely different discussion. In terms of heat produced in the space under led vs hps, they will be identical, as your article points out, the only difference is how you are able to distribute your heat around your grow area. Here's the thing, radiant heat does not stay radiant heat forever. Once it hits something, the heat is absorbed, and then transferred out of that material via conduction and/or convection.

PJ Diaz said:

Thank you for proving my point.

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Yes, you are right.

This discussion, how much heat from led/HPS, a watt is a watt etc, is one of the most controversial subjects I see discussed on the site. It always ends with flame war with both sides convinced that they're right. I've heard of people doing tests, watt for watt, and sometimes HPS comes out hotter, sometimes led and hps the same. Even though I can agree with that a watt is a watt there definitely seems to be more to it. If your slicing hairs a watt is a watt is only true in the same thermal system. As soon as you've changed out the light technically it's not the same system anymore and will behave different. If the hps is heating bulb, tent, reflector and the air in the tent, and the led is heating the PCB, heatsink air and tent it's not the same system is it? It'll still be close, but not necessarily the same. Thermodynamics is easy to put your head around the basics which are very straightforward, but bringing it all to practice is a whole other matter (not that I know the whole deal but I saw my mates exam on it and it was way beyond me). But it's safe to say that there is a lot we don't take into account on the level we're at. Way back when there was a lot of diy and a lot of people (smarter than me) were counting on thermal resistance of heat sinks. Everybody using thermal resistance as a constant when infact thermal resistance changes depending on how many watts a put thru the sink. I added a proper heatsink datasheet here to show the graphs that nobody knew existed.


This is not to flex or anything it's only to show that there are things about thermodynamics that smarter people than me didn't have a clue about and that it's important to understand that in this subject we are all a bit on amateur level.

PJ Diaz: I'm so glad you've done tests, but I feel they would be more interesting to our situation if you kept extraction and fans on. After all were talking about this in a grow context, not in order to prove if physics are "right".

Another issue I've come on to, anecdotally, is ambient temp differences between MH and HPS, watt per watt. I've seen people claim that this difference was down to difference in the arc temp in the coil inside the bulb, MH being hotter. Which kind of makes sense, remember that the 2200K of HPS and +4000k for MH; these numbers refers to the light emitted by a blackbody heated to 2200degrees Kelvin, and would thus be almost the double in MH.

If someone sat down and made some more extensive test my best guess is that we will find both:
- A super strong correlation between watts used and temps inside the growspace. Well obviously. And:
- my guess is that you would also find a correlation between the hottest point of your growlight and ambient temps. And I suspect that this correlation would still be there if you controlled and removed wattage from the calculations. Edit: this latest assuming there is no real airflow over the light/bulb/heatsink.


Edit: big oopise on me, that's the wrong datasheet, the graph is not related to watts. I'll see if I can dig out the right one.

Rocket Soul said:

This discussion, how much heat from led/HPS, a watt is a watt etc, is one of the most controversial subjects I see discussed on the site. It always ends with flame war with both sides convinced that they're right. I've heard of people doing tests, watt for watt, and sometimes HPS comes out hotter, sometimes led and hps the same. Even though I can agree with that a watt is a watt there definitely seems to be more to it. If your slicing hairs a watt is a watt is only true in the same thermal system. As soon as you've changed out the light technically it's not the same system anymore and will behave different. If the hps is heating bulb, tent, reflector and the air in the tent, and the led is heating the PCB, heatsink air and tent it's not the same system is it? It'll still be close, but not necessarily the same. Thermodynamics is easy to put your head around the basics which are very straightforward, but bringing it all to practice is a whole other matter (not that I know the whole deal but I saw my mates exam on it and it was way beyond me). But it's safe to say that there is a lot we don't take into account on the level we're at. Way back when there was a lot of diy and a lot of people (smarter than me) were counting on thermal resistance of heat sinks. Everybody using thermal resistance as a constant when infact thermal resistance changes depending on how many watts a put thru the sink. I added a proper heatsink datasheet here to show the graphs that nobody knew existed.
View attachment 5008135

This is not to flex or anything it's only to show that there are things about thermodynamics that smarter people than me didn't have a clue about and that it's important to understand that in this subject we are all a bit on amateur level.

PJ Diaz: I'm so glad you've done tests, but I feel they would be more interesting to our situation if you kept extraction and fans on. After all were talking about this in a grow context, not in order to prove if physics are "right".

Another issue I've come on to, anecdotally, is ambient temp differences between MH and HPS, watt per watt. I've seen people claim that this difference was down to difference in the arc temp in the coil inside the bulb, MH being hotter. Which kind of makes sense, remember that the 2200K of HPS and +4000k for MH; these numbers refers to the light emitted by a blackbody heated to 2200degrees Kelvin, and would thus be almost the double in MH.

If someone sat down and made some more extensive test my best guess is that we will find both:
- A super strong correlation between watts used and temps inside the growspace. Well obviously. And:
- my guess is that you would also find a correlation between the hottest point of your growlight and ambient temps. And I suspect that this correlation would still be there if you controlled and removed wattage from the calculations. Edit: this latest assuming there is no real airflow over the light/bulb/heatsink.

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Timber wholeheartedly seconds this post by @Rocket Soul - well put and well said.

All systems have their own efficiency level on light output. The standard BTU/watt is for the same for any fixture though heat wise.

Just got a new Lux meter. It tops out a 100k Lux. But I can compare the Lux output of different lights of know wattage.