HID too hot now: What LED layout makes the most sense?

[Zzzax]

Year Five – Reset and Rebuild


I’m in Illinois and fully compliant with the state’s medical grow laws.


Medically, I’m allowed:

• Five plants taller than five inches
• Unlimited plants under five inches

---

Why I’m Changing the Room​

When I first moved here, I reasonably believed I could run HID lighting in my grow room. Given Illinois winters—with snow and occasional single-digit temperatures—it made sense at the time. I also wanted CO₂ enrichment, so I installed an Aries CO₂ burner.


Five years later, it’s clear the climate no longer supports that setup reliably.


Winters aren’t consistently cold anymore. We now get long stretches of mild weather—sometimes t-shirt weather—followed by short cold snaps. During those swings, the combination of:

• twin 1K Hortilux Eye HIDs
• CO₂ burner
• and a concrete floor that stores heat

has pushed room temperatures past 100°F more often than I can manage.


That isn’t healthy for the plants.


So, the decision is made:


Out: twin 1K HID lights
In: a quad-LED layout

---

Lighting Equipment on Hand​

• Four (4) Mars Hydro TS 3000 (420W)
• Four (4) 120W 6000K Daylight Corn-Cob LEDs with reflectors

The grow room is 12′ × 14′, cement floor, with basic ventilation already in place.

---

The Core Question: Light Layout​

I’m looking for advice on light placement.


In a 12′ × 14′ room growing four plants at a time, how should I lay this out?


Let:

• X = TS 3000
• O = Corn-Cob LED

Option 1 – Clustered TS 3000s





|---------O---------|
|-------X---X-------|
|-------X---X-------|
|---------O---------|


Option 2 – Spaced TS 3000s with COBs between





| X O X |
| X O X |


Another idea:

• Hang four TS 3000s, one per plant
• Mount the COBs on the side walls, aimed into the lower canopy and undergrowth

I could also add a fifth TS 3000 and eliminate the COBs entirely—but I already own the COBs, so I’d like to use them intelligently.

---

Constraints and Goals​

• The cement floor stores heat well (great in true winter, bad in warm spells)
• HID made the floor feel hot to bare feet during weather swings
• LED is the only practical path forward under current climate conditions
• I want control, not just intensity

I can legally grow five plants, but:

• Five is an awkward number for layout
• Four plants makes better use of space
• Six would be ideal, but isn’t legal here

So I’ll plan around four plants, with smaller veg or clone plants elsewhere if needed.

---

Thoughts on Veg vs Flower​

GPT-5 suggested that 5000K COBs are useful for vegetative growth, helping keep plants compact.


That leads to another idea:

• Veg under COBs
• Flower under TS 3000s

This mirrors the old-school HID approach of:

• Spring (blue-leaning) → Veg
• Fall (red-leaning) → Flower

It’s appealing, but I’m unsure whether that’s the best use of the room and fixtures.

---

Final Question​

Given:

• four TS 3000s
• four 5000K COBs
• a 12′ × 14′ room
• four plants per cycle
• and a need to control heat

What layout makes the most sense?

 

[Zzzax]

Year Five – Reset and Rebuild


I’m in Illinois and fully compliant with the state’s medical grow laws.


Medically, I’m allowed:

• Five plants taller than five inches
• Unlimited plants under five inches

---

Why I’m Changing the Room​

When I first moved here, I reasonably believed I could run HID lighting in my grow room. Given Illinois winters—with snow and occasional single-digit temperatures—it made sense at the time. I also wanted CO₂ enrichment, so I installed an Aries CO₂ burner.


Five years later, it’s clear the climate no longer supports that setup reliably.


Winters aren’t consistently cold anymore. We now get long stretches of mild weather—sometimes t-shirt weather—followed by short cold snaps. During those swings, the combination of:

• twin 1K Hortilux Eye HIDs
• CO₂ burner
• and a concrete floor that stores heat

has pushed room temperatures past 100°F more often than I can manage.


That isn’t healthy for the plants.


So, the decision is made:


Out: twin 1K HID lights
In: a quad-LED layout

---

Lighting Equipment on Hand​

• Four (4) Mars Hydro TS 3000 (420W)
• Four (4) 250W 5000K Daylight Corn-Cob LEDs with reflectors

The grow room is 12′ × 14′, cement floor, with basic ventilation already in place.

---

The Core Question: Light Layout​

I’m looking for advice on light placement.


In a 12′ × 14′ room growing four plants at a time, how should I lay this out?


Let:

• X = TS 3000
• O = Corn-Cob LED

Option 1 – Clustered TS 3000s





|---------O---------|
|-------X---X-------|
|-------X---X-------|
|---------O---------|


Option 2 – Spaced TS 3000s with COBs between





| X O X |
| X O X |


Another idea:

• Hang four TS 3000s, one per plant
• Mount the COBs on the side walls, aimed into the lower canopy and undergrowth

I could also add a fifth TS 3000 and eliminate the COBs entirely—but I already own the COBs, so I’d like to use them intelligently.

---

Constraints and Goals​

• The cement floor stores heat well (great in true winter, bad in warm spells)
• HID made the floor feel hot to bare feet during weather swings
• LED is the only practical path forward under current climate conditions
• I want control, not just intensity

I can legally grow five plants, but:

• Five is an awkward number for layout
• Four plants makes better use of space
• Six would be ideal, but isn’t legal here

So I’ll plan around four plants, with smaller veg or clone plants elsewhere if needed.

---

Thoughts on Veg vs Flower​

GPT-5 suggested that 5000K COBs are useful for vegetative growth, helping keep plants compact.


That leads to another idea:

• Veg under COBs
• Flower under TS 3000s

This mirrors the old-school HID approach of:

• Spring (blue-leaning) → Veg
• Fall (red-leaning) → Flower

It’s appealing, but I’m unsure whether that’s the best use of the room and fixtures.

---

Final Question​

Given:

• four TS 3000s
• four 5000K COBs
• a 12′ × 14′ room
• four plants per cycle
• and a need to control heat

What layout makes the most sense?

Another thought has come up:
How about using COBS alone for early veg?
Then switch from Blue early in the day to TS 3000s later in the day and then finally all TS 3000 and no COB at all.
That way it starts out spring.. Starts to go Fall and then all Fall "Spectrum" Yeas Stoner thinking there.

that would be like this

|------X--O --X------|
|------O------O------|
|------X--O---X------|

That would cluster Blue for VEG and then later each flowering plant will have it's own TS 3000


Over engineering? Switching from COBS to TS 3000s in a three phase system. Early all Blue.. Then mixed. Half day blue and then TS 3000 then in flower all TS 3000

Your thoughts.

 

[Thukah]

Another thought has come up:
How about using COBS alone for early veg?
Then switch from Blue early in the day to TS 3000s later in the day and then finally all TS 3000 and no COB at all.
That way it starts out spring.. Starts to go Fall and then all Fall "Spectrum" Yeas Stoner thinking there.

that would be like this

|------X--O --X------|
|------O------O------|
|------X--O---X------|

That would cluster Blue for VEG and then later each flowering plant will have it's own TS 3000


Over engineering? Switching from COBS to TS 3000s in a three phase system. Early all Blue.. Then mixed. Half day blue and then TS 3000 then in flower all TS 3000

Your thoughts.

swapping out lights in a single room for a home grow seems like a lot of extra work, (seems I made this up in my head) Id spread out the two color temps as evenly as possible and push higher kelvin in veg then turn it down and turn the 3k up in flower. That's essentially what I did with the 12 cob fixture I made a long time ago and couldn't be happier. Best way to make sure everything is getting equal light is a light meter for sure.

 

[Ninjadogma]

All I read was you can have unlimited plants under 5" tall and my mind immediately went to extreme LST for a couple acres of 4.95" tall cannabis plants.

 

[Zzzax]

All I read was you can have unlimited plants under 5" tall and my mind immediately went to extreme LST for a couple acres of 4.95" tall cannabis plants.

Well,, I believe what I see and read sometimes.
I believe the Illinois law says if they are less than 5 inches ( I assume Tall ) that they can't get you arrested for too many plants.

So, Yeah, if we can get them to grow horizontally then that would be cool.

Edit: They don't make a horizontal LED system yet bummer....

 

[Zzzax]

You know what guys?

I think I smoked a good bud there while I was thinking.

But now I think the TS 3000 can handle both.

I am taking two of the TS 3000s out of the tents so I can put those two COBS in the tents just for VEG.

Sometimes I think too much.

So, I read a lot of posts here and I'm over thinking things.

It's not like 1990 and we are blending RED and BLUE lights to get a full spectrum. The TS 3000 grew some find bud when I decided to grow flower in the tent one year.

I do however like how big colas get under HID. Yet I know the heat is causing those plants stress


So FINAL DECISION : I will work with just the TS 3000s in the room and put the cobs in tents for VEG only.

That is workable and sensible.

Thanks for all the inputs but simple works better.