Grow light help

Hello,

I've been trying to figure some things out about LED grow lights, but I've been unable to find the answers, which suggests I've been looking for the wrong things.
And so, I've been forced to actively approach this community for assistance.

My current setup has a 240w Samsung qboard(LM301H diodes), inside a 80cmx80cmx180cm tent.
I wanted to upgrade the setup to a larger tent now that I'm more confident about my ability, but everything I've found has conflicting info about the lights:
On some sites, that light is enough for a 1m^2 tent, in others, it's underpowered even for my current tent.

I've been considering a 1.2m^2 tent, and for that one I'm positively sure 240w would be underpowered.
Here's my actual question:
It's actually easier for me to get my hands on 120w or 240w qboards than anything with a higher power(both due to price, as well as a general lack of market over here for higher powered lights. For example, the next step up after 240w is a 600w array from Lumatek which costs roughly 6x as much as the 240w qboard).
Would a pair of 240w boards in a tent be the same as a 480w array?
I'm asking because a 1.2m^2 tent has nearly double the area of a 0.8m^2 tent.

tl;dr:
Can I use a pair of 240w qboards in lieu of a 480w led light inside a 1.2m^2 grow tent?

BonkMixer said:

Hello,

I've been trying to figure some things out about LED grow lights, but I've been unable to find the answers, which suggests I've been looking for the wrong things.
And so, I've been forced to actively approach this community for assistance.

My current setup has a 240w Samsung qboard(LM301H diodes), inside a 80cmx80cmx180cm tent.
I wanted to upgrade the setup to a larger tent now that I'm more confident about my ability, but everything I've found has conflicting info about the lights:
On some sites, that light is enough for a 1m^2 tent, in others, it's underpowered even for my current tent.

I've been considering a 1.2m^2 tent, and for that one I'm positively sure 240w would be underpowered.
Here's my actual question:
It's actually easier for me to get my hands on 120w or 240w qboards than anything with a higher power(both due to price, as well as a general lack of market over here for higher powered lights. For example, the next step up after 240w is a 600w array from Lumatek which costs roughly 6x as much as the 240w qboard).
Would a pair of 240w boards in a tent be the same as a 480w array?
I'm asking because a 1.2m^2 tent has nearly double the area of a 0.8m^2 tent.

tl;dr:
Can I use a pair of 240w qboards in lieu of a 480w led light inside a 1.2m^2 grow tent?

Click to expand...

Yes of course but 3 would kill it haha

In theory yes. Might even get a better light spread. However 480 watts would be at the lower end of desirable but it would definitely work.

edit: I actually prefer more lights at lower wattages than one big light. Just my preference.

pegboy said:

In theory yes. Might even get a better light spread. However 480 watts would be at the lower end of desirable but it would definitely work.

edit: I actually prefer more lights at lower wattages than one big light. Just my preference.

Click to expand...

So for a 1.2m^2, 600 or 720 would be preferable?
Would 480 be enough for a 1m^2 tent?

You'll have to convert the math but generally 32-50 watts per square foot is where you want to end up. So you'd be close at 1.2m but 1m might be more optimal at 480w.

this might help.

pegboy said:

edit: I actually prefer more lights at lower wattages than one big light. Just my preference.

Click to expand...

If power access is not a issue then this is not just an oppinion. You will get better distrubution by spreading out the light sources and be able to put the highest concentration areas directly on more plant. You have a higher level of control of power usage and temp regulation. However a high powered light all runs on one plug

pegboy said:

You'll have to convert the math but generally 32-50 watts per square foot is where you want to end up. So you'd be close at 1.2m but 1m might be more optimal at 480w.

Click to expand...

Using that math, 240w is on the lower end for a 0.8m^2 tent.
An easy conversion trick I learned is to just multiply by 10 to get the square footage(it's not accurate, but a reasonable estimate).

But anyway, that's exactly what I needed.

Thanks a lot.

First the maths. I assume you mean the following:

0.8m x 0.8m = 0.64m2

1.2m x 1.2m = 1.44m2

There are also roughly 10 square feet per square meter. So you want at least 480W per 1.2m x1.2m tent, but it also depends on the light – these are ballpark figures.

So two 240W panels will fit the bill. You don't say exactly what lights you have (only HLG makes "real" Quantum Boards – the Chinese use it as a generic term), so I'm going to guess you have some type of rectangular Chinese PCB LED with a 240W driver mounted to either a heatsink or 3mm aluminium board. In any case, hanging two side-by-side should also give you a roughly square-shaped light that will fill the tent reasonably uniformly.

BonkMixer said:

Using that math, 240w is on the lower end for a 0.8m^2 tent.
An easy conversion trick I learned is to just multiply by 10 to get the square footage(it's not accurate, but a reasonable estimate).

But anyway, that's exactly what I needed.

Thanks a lot.

Click to expand...

Multiplying with 11 gets you almost bang on target. A 3x3 is 90x90cm, adding 10cm to two sides adds approx 2 square feet.
Generally youll max out a m2 with 400w (2x200w drivers) but at that wattage you kinda need to have a quite good growgame. But obviously take into account the actual boards: some china boards/lights will only give you 2.2ppf/w while hlg built can get up to 3.0ppf/w: an increase of almost a third.

Another consideration is autos/photoperiod: running the lights for 20h instead of 12h means you can decrease wattage a fair bit. One of my growbuddies managed 350g from only 100w /6 plants in a 80x80cm tent with a light i made for him out of Bridgelux vesta strips. When starting out for the few first times youre likely to yield better with lower light levels, not pusing the plants to the limit. Starting out its way better to focus on getting the environmentals right, temps and rh. Happy growing

11 square feet per meter (10.76 to be precise) is closer, but I use 10 because it's easy to work with. I also agree that up to 400W is about right for a 1m x 1m area and up to 600W is good for a 1.2m x 1.2m area. But it depends on the lights and plants. I grew out some hazes next to some newer Cookies-type genetics recently, and the old-skool hazes wanted up to 1000 PPFD whereas the newer genetics showed signs of stress over 800 PPFD.

I have seen that a lot with modern strains – they don't like as much light as many of the old-skool varieties, and I put this partly down to them being less leafy (higher calyx to leaf ratio), as well as the current trend to mass defoliate. Defoliation removes fan leaves that would otherwise absorb light, leaving a higher concentration of light for the rest of the plant to absorb. (I use the word "absorb" because if light isn't photosynthesied – ie: chloroplasts become saturated – then it is converted to heat which causes the plant to stretch and eventually bleach.)

It is also worth remembering that the larger the area, the fewer watts per square foot you need, as you reduce wall losses. For example, a 1m x 1m area has 4m of wall (4m of wall per square meter), whereas a 2m x 2m area has 8m of wall (2m of wall per square meter) and a 4m x 4m area has 16m of wall (1m of wall per square meter).

Every time you quadruple the tent area, you halve the wall losses. This is important, because there is no such thing as a 100% reflective surface. If your walls are 80% reflective, you lose 20% of all light that hits them. When you halve the wall area, you halve those 20% losses.

350g from 100W is outstanding.