Need help switching to CMH please.

Sammy Snakeskins · Sep 9, 2021

Hi everyone, I've been growing, frankly sh*tty herb for maybe 5 years with LEDs mainly my preferred method. I only do it in the cooler months but now I think it could time for a change. I was going to buy the Mars hydro tsl 2000 with a 2×4 tent but stopped to reconsider.

I think I'm all set to switch to cmh but just one factor that could present a problem for me is the height of my ceiling. I have only 7-8ft. of ceiling height and seeing as I'm a scrOG style grower, I think I can make it work. Does anyone think I'm wrong about this or is there anything I should know? Heat output would be my second worry I suppose.

Idlewilder · Sep 9, 2021

Cmh put out quite a bit of heat and need should 2-3 ft above your canopy. You can grow great herb with better yield. You want to try and keep your temps low 80’s if possible

Sammy Snakeskins · Sep 9, 2021

Idlewilder said:
Cmh put out quite a bit of heat and need should 2-3 ft above your canopy. You can grow great herb with better yield. You want to try and keep your temps low 80’s if possible

I was looking at verticle ballasts and heard tale they can be kept 12-18 in. away from the top of canopy.

Gentlemancorpse · Sep 9, 2021

I've been running CMH for years even in my 5' tent. They can definitely be 18" from the canopy in flower. You shouldn't have any issues.

Gentlemancorpse · Sep 9, 2021

Idle is spot on about the temps though. Unlike LEDs the plants don't like high temps. Anything over 88 they get kind of unhappy, but I've pushed through weeks in the 90s if necessary

Amos Otis · Sep 9, 2021

Gentlemancorpse said:
Idle is spot on about the temps though. Unlike LEDs the plants don't like high temps. Anything over 88 they get kind of unhappy, but I've pushed through weeks in the 90s if necessary

It helps to have your flowering hours happen after sundown and before sunrise. Every little bit etc ...

Sammy Snakeskins · Sep 9, 2021

Gentlemancorpse said:
Idle is spot on about the temps though. Unlike LEDs the plants don't like high temps. Anything over 88 they get kind of unhappy, but I've pushed through weeks in the 90s if necessary

Crap, so this would need to be conducted in the dead of winter cuz my AC is doing awful during this heat wave in Nevada.

Sammy Snakeskins · Sep 9, 2021

Gentlemancorpse said:
I've been running CMH for years even in my 5' tent. They can definitely be 18" from the canopy in flower. You shouldn't have any issues.

Do you mean you've had a verticle or horizontal orientation ballast used at that height???

Gentlemancorpse · Sep 9, 2021

Sammy Snakeskins said:
Do you mean you've had a verticle or horizontal orientation ballast used at that height???

Horizontal. I try to keep it closer to 24" but sometimes the gals get away from me

Gentlemancorpse · Sep 9, 2021

Sammy Snakeskins said:
Crap, so this would need to be conducted in the dead of winter cuz my AC is doing awful during this heat wave in Nevada.

They definitely throw more heat than the LEDs. Probably their biggest drawback. But it's still far less than HPS. If you can pump the air out of the room it helps a lot too.

Sammy Snakeskins · Sep 10, 2021

I'm ready to hit the buy button but im still not sure about what spectrum of bulb to get. There's 3100K and 4200K and it is my impression that both will get the job done till the end.

Idlewilder · Sep 10, 2021

3100k if it’s just for flower. 4200k for veg only. However, I have flowered under a 4k bulb with good results. I’d say if it’s pulling double duty then go with the 4k spectrum

Sammy Snakeskins · Sep 10, 2021

Idlewilder said:
3100k if it’s just for flower. 4200k for veg only. However, I have flowered under a 4k bulb with good results. I’d say if it’s pulling double duty then go with the 4k spectrum

Both it is.

Sammy Snakeskins · Sep 10, 2021

I got the tent at 72" height and thank the good lord this baby has a dimmer switch and a Phillips bulb with it. $250 including tax. Plus $85 for the tent.

Sammy Snakeskins · Sep 10, 2021

The bulb is a f.s. 4000K

Gentlemancorpse · Sep 10, 2021

Sammy Snakeskins said:
View attachment 81465
I got the tent at 72" height and thank the good lord this baby has a dimmer switch and a Phillips bulb with it. $250 including tax. Plus $85 for the tent.

I have that exact fixture. Been using it for about 5 years now, replaced the bulb once. The Philips bulbs are great. I'm running some Vivosun brand bulbs now and honestly wish I had ponied up the extra for the Philips. For whatever reason, the Philips threw less heat and the plants seemed to like it more.

A note on the dimmer.... it's usually advised not to use it. Unlike LED, when you dim HID bulbs it alters the spectrum, so it can slow plant growth and reduce yields. That being said, I've done it in desperate times and it's not like it will kill your plants or anything

Sammy Snakeskins · Sep 10, 2021

Well noted. I don't NEED the dimmer I suppose. I was just thinking of the plants in their adolescence phase.

Idlewilder · Sep 10, 2021

Nice. Imo a ballast is a ballast. Spend the money on Philips bulbs and you’ll be set

Gentlemancorpse · Sep 10, 2021

Idlewilder said:
Nice. Imo a ballast is a ballast. Spend the money on Philips bulbs and you’ll be set

Yup, I have a fancy sunsystem ballast and I hate the design. They enclose the ballast so it gets way hotter than this style. Luckily I got it real cheap lol.

Ramblinrose · Sep 10, 2021

I run a CMH in a 4x4 tent - the ballast is outside of the tent. Temps are usually ~5 degrees above outside the tent with my 4" ac infinity fan at setting 4 or 5 out of 8. For me thats usually high 70s in the tent, so very manageable. First run with this set up has gone very smoothly aside from one issue I had with an oscillating fan that was too intense and caused wind burn. I think if I did LEDs I would have to have a small heater to keep the tent in the ideal ~80 degree range.

Need help switching to CMH please.

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