LED umols and using multiple panels

Is 1200-1500 umol a good number at 18” ? And if I split that between a couple fixtures they don’t add up right? Like 2 leds running 980umol each… plant is not getting 1960 umol right? So if I split lights… they can be lower…?

@dbrn32 will assist you with this mate.

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1200–1500umol is very high, my MarsproII1600led center is 730umol 24’’ , it can work very well. If you use two different light, the led can distribute light more evenly. You can see the edge of light is much lower than the center

Is your Mars light strong enough for flower? So individually my leds run 980umol at 18” @280 actual watts and there’s 3 in a 4x4… should be plenty of light right? Extra light… like I need co2 and they’d take off…?

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Where are you getting the numbers from? When you get a picture like most of the lights on amazon provide, you have to consider what they are sharing. A single point measurement from directly under light at a given distance is really limited information. It’s telling you how much light intensity you have at that point. 1200 umols is a solid number, but you would have to plot readings within your space and come up with a ppfd average before you could really do anything with that information.


correct, the umol’s would not add together if the fixtures r spread apart.

no, they will need to be 12-24" (30-60cm) above the tops no matter how many u have.

disregard the advertised umol numbers,
HPS, T5 HO, and Purple LED need 50-60 watts per square foot for flower,
to fill a 4x4 with enough flower light u would need 800 - 1000 watts,
280w x 3 = 840w so u have just enough light.!
to utilize Co2 u need another 280w light in the tent.

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It’s not a amazon light. Was thinking around 14” would be 1200umol but only for 2’x2’. But there is a pic

Does that not show what you just said.

Ok, I’m wanting max yield… so I need @1000watts and co2… I have 400w,600w &1000w hps… so I’ll just use led to veg…?

Your image didn’t load. So I’m not really sure how to answer you without any information on your light. Who is the manufacturer and what model is it?

You don’t really need co2 until your ppfd average is over 1000 umols per second. Based on what you’re telling me, I don’t believe your light would provide that in a 4x4. But I’d like to know what we’re looking before I say that for sure.


Not sure, can’t remember/find the paperwork they came with but I’ll look… ok, so >1000 umol for co2…? What’s the umol rating of a 600w hps?1000w? Should I add a 600w MH (dimmable) at 50% along with leds? Having to add heat to tent as it is anyways… how many umol would PAR 2170 be?

Greater than a ppfd average of 1000 umols per second. You would need integrated sphere data or an extensive par map to calculate that. You can’t simply determine from a single spot measurement taken directly under the fixture.

I don’t know what par 2170 is? Is that a light model? A really good horticulture specific 600 watt hps bulb will have a ppf of around 1000 umols per second when it’s new. That means to have a ppfd average of 1000 umols per second per square meter it would have to be in a 39”x39” space.

Ok. On the led box it says 1.5m2. Lx=12500. PAR=2170. What is that in relation to ppfd? Basically what value or number for led compares to a 600 watt hps/mh? 980 is umols close to the 600w hps output, correct?

That number is equivalent to a 150 watt cfl. Although it’s not an accurate comparison if you’re using a blurple panel.

Ppf and ppfd are two different things. Like I said earlier, if that’s a spot measurement taken directly from under your light it doesn’t really help you any. Ppf is total amount of light emitted. They measure it by placing the light in a highly reflective completely enclosed sphere and collect all of the light within the par range.

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Ok, so what number am I looking for when looking at led for say, a 4x4’ tent? Enough light to utilize co2… umol? Ppfd? Par?

A ppf is the easiest way. This light is designed for a 4x4 and timber gives you supporting ppf data.

Cool! Thanks! So for a 4x4’ if my light says 908 umol at 18” above canopy then that’s a good light to use? Wouldn’t 2 of them be better?

Depends on whether 908 is the ppf, or it’s a single point reading directly below the light.

Who is the manufacturer of your light and what model is it?

Mars hydro 720w reflector…

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It’s s 315 watt light, most of those lights test out around 1.2 umol/joule. Being generous, it probably has a total ppf between 375 and 450 umols per second. Mars claims it to have a flowering intensity good to 2’x4’, which is probably a little bit of a stretch. It’s definitely not going to be requiring co2 in something like a 2x4 though.

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I’m quickly deciding that led is a bunch of crap. They are not advertised right and for $300 I should be getting more than a 2x4 inadequately lit. 600 w MH/hps… the most efficient light that you don’t have to decipher a bunch of numbers that are wrong anyways!!!

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