315Watt CMH Lighting: Specs, Coverage, Pics

Tony Urban · May 5, 2019

I went and picked up a 315w CMH a few weeks ago for this next crop. I will run both, an LED and the CMH for overkill and overall coverage. Plenty for the 3 x 3 tent lol

I will run the Perfect Sun Dwarf Star next to the CMH

Stunned · May 5, 2019

Lowrider72 said:
Nice buds mate. That GSC is a killer frosty strain. Quantums are pretty good, seen some decent grows.
How many watts of quantum and what size area?
Can you cover 4' x 4' in Flower with less than 315w? Its about weighing all that up.
Not knockin ya smoko but...mmmmm....
lol

3 fixtures
2 at 230 watt
and 1 at 275ish....
in a 5X5
I could crank up all 3 fixtures
but don't need to from what I'v seen

I like cmh

TheFertilizer · May 5, 2019

Weaselcracker said:
It’s not just Wikipedia. It’s all over. Here’s the CMH info from over on the GWE site- usually a source of solid info .

“ Unfortunately, LEC grow lights don’t quite get the same yields as HPS grow lights of similar wattage when used as the primary light in the flowering stage. However, they do get significantly higher yields than a similar wattage Metal Halide bulb would get in the flowering stage...”

Yeah I have heard a lot of mixed reviews about that.

By the numbers though, from what I've seen with PAR testing, a 3100K CMH outperforms a 400 W Hortilux HPS by a small margin. Those are the top of the line $70 HPS bulbs, but they didn't test any of the more economically priced ones. However, with the longevity considered, a HPS bulb has about a 10k hour lifespan, while the CMH bulbs still have 80% of their original output even at 24k hours. Meanwhile they're about the same price as that $70 HPS.

I'm not convinced they'd replace a 600 W hps but I don't have practical experience with either... But everyone I've heard that talks about them says that a 315 W CMH will yield the same as a 600 W HPS. I don't know if they've done side by side comparisons, but that's basically what convinced me to switch. That and the fact that CMH is supposed to run as hot as MH, and not as hot as HPS, which I kind of needed for environmental control.

Anyway, I haven't seen a huge difference in yield, and I use to run a 400 W HPS with just generic Apollo bulbs. I mean, most of my crops with the CMH have been smaller, but I've also been growing in less than optimal mediums, in small pots, etc. On the other hand, the bud I've grown with CMH has been noticeably better. It's just as dense, not fluffy or anything like that, but it is MUCH more resinous and sticky. Having talked to a lot of older growers, that seems to be down to the blue spectrum. Red spectrum has gotten a lot of hype as being the best to grow bud with, but that's mainly just because everyone got use to HPS delivering the most yield. I have actually had a lot of people asking me how I'm getting shit so sticky and saying they haven't seen stuff like that in 20 years etc. I think that has a lot to do with HPS having been the de facto "best" for about the last 20 years. My last cycle especially, I used the CMH along with some T5 so there was a lot of blue, and that shit was so sticky you could press it up against glass and it would just sit there.

So anyway I'm blabbing... OH yeah the weirdest shit with CMH is that plants don't seem to stretch under it. Like, say you took a MH or an HPS, and you stuck seedlings under it and you put that light as high as it could go in your tent. Your seedlings would stretch and fall over right? Not under CMH. They stay short and squat just as if they were growing out under the sun. It's bizarre, but I think it's just because if you look at the distribution of CMH's spectrum, it's a lot closer to what plants naturally expect from sunlight than HPS or MH, and perhaps a lot of LEDs.

I got a "conversion kit" type of setup where they give you a little adapter so you can plug the CMH lamp into an ordinary mogul socket, so that you can take your current MH/HPS setup and just pop the CMH right in place of the lamp and ballast that's already in place. Cost me $200 and I've already used it for 3 pretty good cycles.

Lowrider72 · May 5, 2019

Sorry, wasn't ignoring anyone, was just reading all the opinions....

UrbanAchiever said:
I went and picked up a 315w CMH a few weeks ago for this next crop. I will run both, an LED and the CMH for overkill and overall coverage. Plenty for the 3 x 3 tent lol

I will run the Perfect Sun Dwarf Star next to the CMH

Hey Urban , Welcome!
Maybe the 315w in a 3' x 3' will be heaps enough. Mine are in 4' x 4'. In your size one should crank and the led might not be needed, just hope you dont get probs from too much intensity, thats all.
Your goung to love it, so happy for you.

Stunned said:
3 fixtures
2 at 230 watt
and 1 at 275ish....
in a 5X5
I could crank up all 3 fixtures
but don't need to from what I'v seen

I like cmh

So you probably run 600w in 5x 5...thats pretty good.
At 630w I run 4 x 8'.

TheFertilizer said:
Yeah I have heard a lot of mixed reviews about that.

By the numbers though, from what I've seen with PAR testing, a 3100K CMH outperforms a 400 W Hortilux HPS by a small margin. Those are the top of the line $70 HPS bulbs, but they didn't test any of the more economically priced ones. However, with the longevity considered, a HPS bulb has about a 10k hour lifespan, while the CMH bulbs still have 80% of their original output even at 24k hours. Meanwhile they're about the same price as that $70 HPS.

I'm not convinced they'd replace a 600 W hps but I don't have practical experience with either... But everyone I've heard that talks about them says that a 315 W CMH will yield the same as a 600 W HPS. I don't know if they've done side by side comparisons, but that's basically what convinced me to switch. That and the fact that CMH is supposed to run as hot as MH, and not as hot as HPS, which I kind of needed for environmental control.

Anyway, I haven't seen a huge difference in yield, and I use to run a 400 W HPS with just generic Apollo bulbs. I mean, most of my crops with the CMH have been smaller, but I've also been growing in less than optimal mediums, in small pots, etc. On the other hand, the bud I've grown with CMH has been noticeably better. It's just as dense, not fluffy or anything like that, but it is MUCH more resinous and sticky. Having talked to a lot of older growers, that seems to be down to the blue spectrum. Red spectrum has gotten a lot of hype as being the best to grow bud with, but that's mainly just because everyone got use to HPS delivering the most yield. I have actually had a lot of people asking me how I'm getting shit so sticky and saying they haven't seen stuff like that in 20 years etc. I think that has a lot to do with HPS having been the de facto "best" for about the last 20 years. My last cycle especially, I used the CMH along with some T5 so there was a lot of blue, and that shit was so sticky you could press it up against glass and it would just sit there.

So anyway I'm blabbing... OH yeah the weirdest shit with CMH is that plants don't seem to stretch under it. Like, say you took a MH or an HPS, and you stuck seedlings under it and you put that light as high as it could go in your tent. Your seedlings would stretch and fall over right? Not under CMH. They stay short and squat just as if they were growing out under the sun. It's bizarre, but I think it's just because if you look at the distribution of CMH's spectrum, it's a lot closer to what plants naturally expect from sunlight than HPS or MH, and perhaps a lot of LEDs.

I got a "conversion kit" type of setup where they give you a little adapter so you can plug the CMH lamp into an ordinary mogul socket, so that you can take your current MH/HPS setup and just pop the CMH right in place of the lamp and ballast that's already in place. Cost me $200 and I've already used it for 3 pretty good cycles.

Cheers mate, Im not so good at explaining things. Thats one of the fairest opinions I have seen.
Do you get a lil grin on your face when you know how happy they will be when they try a new CMH.... We know the joy, Fert.
hehe.

CMH Brutha from another Mother...

LiberalThinker · May 5, 2019

falstaffo said:
i looked at cmh
heat and size were main factors steered me away actually
probably a little cheaper to setup than the qbs i got, but there is literally so little heat from the qbs, which in a loft space willbe great in summer, and also they are so shallow, i have massive height troubles so the big chuncky cmh took too much away.
they look real nice though i must say, but id have needed 2 minimum in my flower tent plus another for veg.

You could get a remote cmh ballast and parabolic reflector with an adapter for a single-ended cmh bulb. That would mitigate the heat away from the canopy - if you choose a reflector with vent holes in the top - and also allow the light to be lower.

Tony Urban · May 5, 2019

Well the CMH couldn’t possibly give me less yield than I am already getting from my LEDs. One of which is a sponsor light.

It goes beyond just the benefits to the plants too, I picked one up to be better for photography, the whiter light makes for better images and easier colour corrections

Weaselcracker · May 5, 2019

falstaffo said:
so i went and had a look at the cost, and compared to my cost and worked out the cost watt for watt, its almost bang on 30% cheaper for cmh
lets assume 1 watt of qb led is 100 units 1 watt of cmh is 70 units..

edit
that is for quantum boards already made, only one needed assmbling took 10mins, the others ready to go, and for cmh at the high end of the range; cheaper versions ofc but i went with more expensive for truer comparison

Maybe I see what you mean now. When I quickly google CMH a bunch of 315w kits pop up for around $250 Canadian. But yeah- when I dig deeper I see some more expensive kits including the Hortilux 315w which is around $650. Not sure what you get for the price difference.

HLG Canada sells a QB300 for $880. Less wattage than the CMH though- at around 275w max. The cost for me after tax and shipping would be at least $1100 each, probably more. I’d need at least three of them to cover my flowering room- though in a perfect world I’d prefer more. Then I’d need to add heat. No way I’m paying that much for my lights though.

Seems like if I want to upgrade I’d be best using CMH, along with some added Q boards once I find some better prices.

Bigjake8 · May 6, 2019

I have been running a phantom kit for almost 2 years now when I did finally run out of room and flowered with it got 12 Oz's off it in a 39x39 tent might as well say a 3x3 now the 1k hps I got in a 5x6 I got 22 same strain same dwc but with around 650 less watts
The question I got is why have I been wasting money on cheep leds when what I have seen tell me that I need to start getting a few more I'm betting 2 will rock my flower room

PS also get better coloring (purpleing tops) with cmh

Lowrider72 · May 6, 2019

Just a couple 615w CMH Tent shots... Week 6 Day 2.......

Week 6 Day 2 CMH 615w

Lowrider72
May 6, 2019

Week 6 Day 2 Budshots

Lowrider72
May 6, 2019

Enjoy!

Lowrider72 · May 9, 2019

Week 6 Day 6... Just after defoilage.
630w total CMH, 4ft x 8ft....

Under bud shot of clean up.

Lowrider72
May 9, 2019

New left side of tent.

Lowrider72
May 9, 2019

New Right side of Tent.

Lowrider72
May 9, 2019

Trimmed Tent Shot.

Lowrider72
May 9, 2019

Enjoy!

LR72.

Weaselcracker · May 9, 2019

Looking good. :thumb; What do you have growing there?

Lowrider72 · May 9, 2019

Weaselcracker said:
Looking good. :thumb; What do you have growing there?

Hey mate Cheers,
In that last shot, 2 on the left are Peyote Critical, next front White Widow, back Gelat OG, then back Gelat OG, front White Widow, then front White Widow, then back Pineapple Chunk.... Phew....
hehe.

Grassmaster · May 11, 2019

falstaffo said:
so i went and had a look at the cost, and compared to my cost and worked out the cost watt for watt, its almost bang on 30% cheaper for cmh
lets assume 1 watt of qb led is 100 units 1 watt of cmh is 70 units..

edit
that is for quantum boards already made, only one needed assmbling took 10mins, the others ready to go, and for cmh at the high end of the range; cheaper versions ofc but i went with more expensive for truer comparison

But the Quantum board or Cob has an efficiency of 2.0 and the CMH only (1.3). And the CMH radiate heat which isn't good unless you have cold weather. You waste even more money on air conditioning.

So in the long run you will pay more for the CMH.

I use my CMH only when it is very cold. Then switch over as soon as possible.

falstaffo · May 11, 2019

Grassmaster said:
But the Quantum board or Cob has an efficiency of 2.0 and the CMH only (1.3). And the CMH radiate heat which isn't good unless you have cold weather. You waste even more money on air conditioning.

So in the long run you will pay more for the CMH.

I use my CMH only when it is very cold. Then switch over as soon as possible.

very true, however, on the flip side, if you are running qbs and have colddd weather you may need to run a heater.. lol
alls i know is you need sunglasses.

Grassmaster · May 11, 2019

falstaffo said:
very true, however, on the flip side, if you are running qbs and have colddd weather you may need to run a heater.. lol
alls i know is you need sunglasses.

But that's at most 2 months out of the year for me. Then I put the CMH inside the 3' by 3' tent and it keeps it at 78 degrees. The plants will go dormant if it gets under 68 degrees or so.

And as an added bonus I can move my cobs 1.5 feet away from the plants and turn it down to less than 100 watts the first month.

Lowrider72 · May 11, 2019

Grassmaster said:
But that's at most 2 months out of the year for me. Then I put the CMH inside the 3' by 3' tent and it keeps it at 78 degrees. The plants will go dormant if it gets under 68 degrees or so.

And as an added bonus I can move my cobs 1.5 feet away from the plants and turn it down to less than 100 watts the first month.

I hear you on that. I take a couple months off because its WAY too hot.
Heat makes Cannabis suffer indoors.
In that time I sort my moms and get veggers ready.
Only reason I would want an LED panel or cob....is to do that or flower through that time.
With CMH I manage to keep everything tip top with NO enviromental control at all, all year. In fact the cold is good for them and keeps my mums slowed down..under LED, because its cold.

Heres the secret to Cannabis, ask any DWC grower, good root condition and a steady temp like in the ground.
The rest of the plant can withstand heaps in nature.

I will try LEDs at some stage, but still watt for watt, CMH seems to have a few advantages.
Punch.....LEDs lack it under 300w
Real 1.72u/mol -Watt......figures I question in accuracy of in LEDs around 3-4u/mol-watt at less wattage.
CMH 315w can spread 550u/mols over 4' x 4' ......can 300w of LED do that, NO.
probsbly only directly underneath it.

Theres a LOT of marketing and a LOT of gaps in fact.
My CMH 615W tent grow will sort the men from the boys. I'll show you LED crew some REAL frost.
LED couldnt even get its shit together until they copied full spectrum CMH.
Blurples.......bwahahaha....

Weaselcracker · May 11, 2019

Ya know, as much as I’m keen to pull the trigger on some CMH lighting, I’ve been out reading through articles on CMH for a couple years now, and they always cite the same info about it being inferior to HPS in flowering, due to HPS having a better red spectrum. If it was just a couple websites saying this I could chalk to up to outdated misinformation. But no, this is pretty much every current article I read on the topic. Hard to just ignore it, and I don’t have a pet lighting expert to ask about this. I wish I did. But the net is my only source of info. So what gives? :hmmmm:

Lowrider72 · May 11, 2019

Weaselcracker said:
Ya know, as much as I’m keen to pull the trigger on some CMH lighting, I’ve been out reading through articles on CMH for a couple years now, and they always cite the same info about it being inferior to HPS in flowering, due to HPS having a better red spectrum. If it was just a couple websites saying this I could chalk to up to outdated misinformation. But no, this is pretty much every current article I read on the topic. Hard to just ignore it, and I don’t have a pet lighting expert to ask about this. I wish I did. But the net is my only source of info. So what gives?

Its like full spectrum LED , its a different system to ol skool hps etc.
The red spectrum is needed and on past pages I have included the spectrums for yoy to look at.
The sun is where its at. It has everything a plant needs.
Both LED and CMH require a grower to become a better grower and concentrate on even canopy and a shorter structure.
Not just smash big plants and get a few big tops and fluff for miles underneath.

Oh and by the way I have an Electronics Cert, and my mate was a tester at Gavita.
So I dont talk shit and dont care for so called experts. Net is full of tossers.
I believe in solid electronic and electrical theory.

kentboy1296 · May 12, 2019

Hey man, you got some wicked ass plants, i currently grow dwc (1st time) growing White Widow myself from growers choice gonna start a mother of the ww (dont wanna loose the genetics) but im gonna do so in coco (never tried) gonna check your grow out, looks amazing and not to complicated at all, i feel that simpler is better, (less to go wrong)