Someone want to school me on CMH?

Looking for some info on HID lights specifically CMH. I'm a new enough grower that all my lights are LED (Diy COB and qB style lights) I'd like to supplement with some HID's for the heat they provide as I'm running heaters and think the electricity would be better used as dual purpose heat + light.

I'll probably use them for veg on a 20/4 or 24/0 schedule just for the heat. Should I just use an HPS?

Thanks

I don't know about CMH, but for veg Metal Halide is better than HPS.

ignatiousR said:

Looking for some info on HID lights specifically CMH. I'm a new enough grower that all my lights are LED (Diy COB and qB style lights) I'd like to supplement with some HID's for the heat they provide as I'm running heaters and think the electricity would be better used as dual purpose heat + light.

I'll probably use them for veg on a 20/4 or 24/0 schedule just for the heat. Should I just use an HPS?

Thanks

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Cmh is the closest spectrum to actual sunlight and is 50% efficient (like a cob chip driven above suggested peak efficiency range). This would be an ideal veg or flower light. You need to be careful with canopy height, theres a good dose of UVB in them that can stress out or burn your plants if too close. If the setup you purchase comes with a bulb, just rock it. If given the choice, the phillips mastercolor 3100° is far superior to any other bulbs that have come out and specifically made for agriculture. Dont let the spectrum temp fool you. Though that sounds like a flowering spectrum, there is more than enough blue in there for any purpose. Kelvin temp is how the light is seen by human eyes, not what the light is made up of. Sun spectra made some great setups that are priced affordably.

a 400 watt MH light + mag ballast will give you more heat than CMH, and later you can swap the MH bulb for a 330 watt mogul base CMH bulb from Philips.
https://www.1000bulbs.com/product/59300/MHS-232595.html

MarWan said:

a 400 watt MH light + mag ballast will give you more heat than CMH, and later you can swap the MH bulb for a 330 watt mogul base CMH bulb from Philips.
https://www.1000bulbs.com/product/59300/MHS-232595.html

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A low frequency square wave ballast, like the ones made for cmh lights is ideal. Watts=heat so yes, but marginal. If heat were the concern alone, you would be best off going with hps because of the large amount of IR. With the ballast in the room and the hood not cooled you will get the benefit of 315+ watts of heat with a better spectrum of light and a higher percentage of that wattage/heat coming in the form of plant usable photons. Thats my outlook on it anyway. Im just not a fan of hps/mh lighting with better options available. I do like seeing that in place of a space heater though. At least that makes it duel function. A propane CO2 generator would also be a good source of heat if you already had enough light. Better suited for flower though. Plenty to chew on with this situation!

Cletus clem said:

A low frequency square wave ballast, like the ones made for cmh lights is ideal. Watts=heat so yes, but marginal. If heat were the concern alone, you would be best off going with hps because of the large amount of IR. With the ballast in the room and the hood not cooled you will get the benefit of 315+ watts of heat with a better spectrum of light and a higher percentage of that wattage/heat coming in the form of plant usable photons. Thats my outlook on it anyway. Im just not a fan of hps/mh lighting with better options available. I do like seeing that in place of a space heater though. At least that makes it duel function. A propane CO2 generator would also be a good source of heat if you already had enough light. Better suited for flower though. Plenty to chew on with this situation!

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I own a couple of Philips LFSW ballast to run 2 315 watts cmh 4100k (mogul) and love them, the ballast do not get hot at all, unlike the mag ballasts which I used to quick dry my buds on. I can feel heat on my neck and arms when working under CMHs unlike a 400 watt HPS.
I recommended CMH so he can veg with, throw in a mag ballast in the tent and it will get warm quick

Thanks for the info guys! @MarWan or @Cletus clem would either of you guys like to recommend a setup?
Another question; what's the difference between the Chinese lights like Apollo and Vivosun vs the more expensive ones, besides the bulbs they come with?

ignatiousR said:

Thanks for the info guys! @MarWan or @Cletus clem would either of you guys like to recommend a setup?
Another question; what's the difference between the Chinese lights like Apollo and Vivosun vs the more expensive ones, besides the bulbs they come with?

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glad to help with what I can

If you already got an old hood or reflector for HPS or MH, this might be best for you
https://growershouse.com/ceramic-science-315w-cmh-light-conversion-kit
you will need a bulb with that.

if your budget is good go for SunSystems.

I would stay away from products from china if you have other local options, mainly for warranty reasons.

I was going to suggest sunspectra but it looks like they are no more hope mine last a bit! Seem like great setups. Well then, what he said! Lol

I use just a cheap 400w CMH from htg, use it in veg and love it

Just noticed this one


Growers Choice 315W Ceramic Metal Halide CMH Lamp 10000k

Growers Choice 10k 315W MH Finishing Lamp helps increase the resin production of your plant in its final stages of Flowering! Growers Using CMH or LEC Fixtures can gain the benefits of the industries first and only 315W 10K MH Finishing Lamp.

Unfortunately I don't have a fixture to retrofit. I'm undecided between a 315 cmh vs an expensive de 1000w vs a really cheap 600w. My electricity is pretty cheap and I'm running a 600w heater to stay warm right now (on thermostat, not full blast)

HID's are about 50% efficient so 1000w makes 500w light and 500w heat right?


Couldn't find info on 10K bulbs only stuff relating to aquariums and growing coral. Seems pretty far off from the spectrum most people use for plants. What's up with that?

ignatiousR said:

Unfortunately I don't have a fixture to retrofit. I'm undecided between a 315 cmh vs an expensive de 1000w vs a really cheap 600w. My electricity is pretty cheap and I'm running a 600w heater to stay warm right now (on thermostat, not full blast)

HID's are about 50% efficient so 1000w makes 500w light and 500w heat right?


Couldn't find info on 10K bulbs only stuff relating to aquariums and growing coral. Seems pretty far off from the spectrum most people use for plants. What's up with that?

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Closer to 35%, mostly heat. CMH and LED start getting into the 50% range. The 10k bulbs are for finishing, the last 2 weeks. The high amounts of blue and UV are said to increase color and resin production if you finish with them. Seems redundant if already running cmh as it already does pretty well in that category. Watts=heat anyway you cut it, the IR light from hid will concentrate that heat on the canopy.

ignatiousR said:

Unfortunately I don't have a fixture to retrofit. I'm undecided between a 315 cmh vs an expensive de 1000w vs a really cheap 600w. My electricity is pretty cheap and I'm running a 600w heater to stay warm right now (on thermostat, not full blast)

HID's are about 50% efficient so 1000w makes 500w light and 500w heat right?


Couldn't find info on 10K bulbs only stuff relating to aquariums and growing coral. Seems pretty far off from the spectrum most people use for plants. What's up with that?

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1 watt = ~ 3.4 btu British Thermal unit.

so 1000w would make ~ 3400 btu in heat. you will need at least 36 inches between light and canopy.
a 316 would make 1074 btu.
a 600 = 2040 btu.
HIDs at best are 40% efficient, I could be totally wrong though .

Veg under fluorescent tubes until 18 inches, then phase in the CMH/LEC. The clones, seedlings, and smaller plants do better under fluorescent until they get stealthy enough for the brightness of a CMH. But once they get a few feet tall they thrive under CMH/LEC like no other light out there. I got 6-foot plants in 60 days from seed with fluorescent for 30 days and then CMH for 30 days. I've used all the other lights out there and these are the best in my experience. You don't even have to change the bulb for bloom. Not to mention the savings on air conditioning because they run cooler.

63 days from seed under two CMH 315's.

I get the CMH 315's off eBay for $189 with free shipping. They come with a hood, 3100k bulb, timer, and two rope hangers. I have four of them and they are awesome! Best lights I've ever owned, cheap to run, and inexpensive to buy. How can you go wrong?