315w CMH/LEC vs 600w HPS

[Sir PsychoHashy]

According to marketing blurb, 315w CMH lights are meant to be equivalent to a 600w HPS.  Now, I've always been cynical about those claims, just like the similar claims being made by LED manufacturers, but never thought that necessarily made them bad lights.  LED's and their particular pros and cons mean they aren't what I'm looking for, but the CMH lights seemed to be, so I bought a couple of Hi Par 315's to have a crack.

 

I've been growing under 2 x 600w HPS in a 1.2*2.4*2.0 tent for a while now, so have a very good idea what to expect.  Best yield was 1200g, worst 980g, but generally I hit 1100g ish.  As some of you know I'm one of those idiots that likes to do multi strain grows, which means compromises and assorted problems, all of which mean I could improve yields with single strain grows, but I love making my life difficult, and love variety in the stash even more, but I still manage an average yield around 1100g consistently unless I have a couple of visits from the Fuck Up Fairy.

 

So a 4 strain grow with 5 distinct phenotypes was the test grow for these lights, pretty standard stuff, in coco/perlite fed via Tropf Blumat Drippers as usual, with my usual EC of 1.2-1.3 and normal nutrient and pest control regimes.  Usual mix of medium and good yielding plants, plus one plant having an unexpected under stretch, and one an unexpected over stretch.  Short version, everything as normal and average.

 

Ended up with a fully filled space, nice even bud spacing, blah blah, and except for the under stretcher one of the better SCROG's I've ever managed:  Pic of a bit after mid flower stage.

 

 

So, whilst I could have achieved a bit better if everything went perfect, I'm comfortable calling this well and truly good enough to be called average, and therefore directly comparable to previous average grows.

 

Yield came in at 920 grams, or 180g below average, which roughly equates to a 20% reduction in yield.

 

So, whilst I'm calling bullshit on marketing claims, I'm still impressed, and see it as about as good as I could have expected from 630 watts compared to 1200 watts.  And further to this, I will add that there are more important things than yield, and for me at least these lights delivered other extra benefits compared to HPS.

 

For starters, my plants stayed lush and healthy right through to late flower, which is something I've never achieved under HPS before, only outdoors.  I put that down to issues with low humidity which HPS only seems to add to in my local climate.  This is my 1st crop to have zero loss to mould, yes I usually only lose a quarter to half an oz but it's still significant.  Resin production looks to be slightly improved as well, which is a big deal for me, and smells and taste also seem to be deeper and nicer like outdoor plants tend to be.  And finally the stone seems to be more complete and nicely rounded, also in the manner of outdoor plants.

 

I put those things down to these lights having a spectrum which is supposed to be close to natural sunlight.

 

Only problem I see with these lights is a matter of pure power.  A bit like comparing a 3l German V6 to a 5l Yank V8, the V6 performs great and is a lot more efficient, but when it comes down to pure output nothing beats a muscle car.  And this was apparent from about the time of the above pic, everything was lovely but I could tell looking at bud size that they just weren't as big as normal at that stage.  Bud density was as normal, resin production was great, but they just weren't pumping up quite as much as they should, so the 20% yield reduction was no surprise.

 

I love these lights, and will continue to use them, but mainly due to my local climate rather than saving electricity costs.  The significantly lower (and I mean significant) heat output in my situation is extremely valuable, but in a more temperate and humid coastal environment it would be much less of an issue.  If I moved to the coast I'd still use them due to the other benefits, but I wouldn't be so keen to drop the coin on them over HPS in that situation.  So in tems of recommending them to others or not, I'd say research their pros and cons and your particular situation and make your own judgement.  They are awesome lights, but just don't pack the same punch.

 

I have used 400w HPS, and these are a much better light in that situation if you can afford to buy them.

 

One issue is with different globes.  I ran the flowering globe (930 from memory) for the whole grow, and veg growth was much slower in an upward direction, but node numbers were at a standard rate if that makes sense?  Very tight structure, which is not necessarily a bad thing indoors, but this was possibly just a little too tight.  Did come out nicely at stretch though, and stretch was a little more manageable than under HPS.  I think the 942 globe is for veg, but at $180 a globe I just don't see the value for something that's used for 3-4 weeks instead of just vegging for a week longer.  I feel the same about the 10,000 globe you can get for finishing off flowering last couple of weeks, but I don't have much money.  My future thought is to start off under HPS for a couple of weeks rather than buy extra globes and then give them a week or 2 under CMH before flipping.

 

My other future thought is to run 3 CMH instead of 2.  945w is still significantly less than 1200w, and the heat output will still be significantly lower.  I noticed that the plant in the middle getting the crossover light performed much better on bud size, so I reckon that would be enough to push yield well over my HPS average whilst still retaining the other benefits of these lights.

 

On the temperature output issue.  During the warmer weather these lights raised tent temps above ambient by very little compared to HPS, 4-6 degrees compared to 10-12, and that's running a lower fan speed than I would with HPS.  So in hot weather these are worth their weight in gold, and hot weather is 3/4 of the year here.  When temps dropped though, I'd have to say I started to miss my HPS lights, these just don't pump out much heat at all, probably about the same as a 250w HPS going on back of hand test and tent temps.

 

Hope this info helps some of you with decision making, and I'm happy to try and answer any questions.

 

[phenix]

Good summary Hashy though I can't recall coming across any marketing hype comparing 315W CMH to 600W HPS in all my research.  In this country?  or overseas? 

[MediKat]

Well done Hashy, think you covered all bases for the punters. 

[hydrochronic]

Great write up and summary, sounds like a good and fair comparison and anayisis of the pros and cons, thanks mate!

[Partimus]

Great summary hashy, cheers for the effort and thanks for sharing with us

 

Those tent dimensions are what I am looking at upgrading to in the near future and that is a very decent yield for a 630 watt output, be very interested to see how much a third light boosts it.

 

cheers

[Carnage]

they used to say the 400watt cmh globes for the old 400w magnetic ballasts were up to par w/ a 600w hps in terms of yield for most but not all phenotypes.

I looked at a 315w lamp as an annoying addition to the market.

I have to buy new ballasts now to go w/. Before I had these 2 ballasts I could slam a couple hot 400w cmh's in.

so if you divide 100 by 400 then multiply that by 315 , you are left w/ the percentage I thought a 315w was compared to a 600w for output.

 

still good isn't it ?

 

100 / 400 * 315 = 78.75%

 

315w cmh I thought was 78.5% of the power of the 600w in terms of photons..

315w cmh uses only 52.5% of the power-draw from the wall as the 600w does.

 

best part is i look at a 630w cmh like its a 1000w hps

 

he he

[Sir PsychoHashy]

Good summary Hashy though I can't recall coming across any marketing hype comparing 315W CMH to 600W HPS in all my research.  In this country?  or overseas? 

 

Probably could have worded that better, and it's possible my crusty old memory's gotten some shit mixed up .  Some of it was claims and inferences by manufacturers/retailers, some from forum discussions around the world, and some's the way my stoner brain mixed it all together, but the general impression that seems to be out there is that they are a direct replacement effectively for a 600 HPS.  In terms of footprint I'd agree, and maybe that's more what was meant by manufacturers???  But whatever, in forums there's a lot of people making the claims that they do the same job.  It was near a year ago I stopped reading and made a decision, so I can't remember where I got my original info from.  If I can be bothered one day, I'll go have a look to provide some better clarity.

 

Well done Hashy, think you covered all bases for the punters. 

 

Great write up and summary, sounds like a good and fair comparison and anayisis of the pros and cons, thanks mate!

 

Thanks guys, just wanted to try and put a realistic appraisal out there instead of marketing or hypothesis, which the internet seems to be full of.

 

Great summary hashy, cheers for the effort and thanks for sharing with us

 

Those tent dimensions are what I am looking at upgrading to in the near future and that is a very decent yield for a 630 watt output, be very interested to see how much a third light boosts it.

 

cheers

 

I find it a good size space for personal grows, allows for enough variety and a bit of room to adjust for the unexpected, without being big enough to look like, or tempt, commercial operations.  If you're only worried about quality, and power savings are more important than big yield, then running the 2 in there will do the job nicely.  But I am confident that a 3rd light will give that little extra intensity to fatten the buds up to the equivalent of 1200w HPS, which does work very nicely in that tent when ambient temps are low enough.

 

And I do still swear by HPS lights, they may be cheap and nasty, but they will consistently pump out great results.  But as someone who prefers the taste and stone of outdoor grows, the CMH lights have allowed me to produce something fairly equivalent indoors, which is awesome.  There is a part of me that's a bit sad at not getting the usual fatness in my buds though, even if it isn't that important.

 

they used to say the 400watt cmh globes for the old 400w magnetic ballasts were up to par w/ a 600w hps in terms of yield for most but not all phenotypes.

I looked at a 315w lamp as an annoying addition to the market.

I have to buy new ballasts now to go w/. Before I had these 2 ballasts I could slam a couple hot 400w cmh's in.

so if you divide 100 by 400 then multiply that by 315 , you are left w/ the percentage I thought a 315w was compared to a 600w for output.

 

still good isn't it ?

 

100 / 400 * 315 = 78.75%

 

315w cmh I thought was 78.5% of the power of the 600w in terms of photons..

315w cmh uses only 52.5% of the power-draw from the wall as the 600w does.

 

best part is i look at a 630w cmh like its a 1000w hps

 

he he

 

That's a great way of looking at it Carn, and pretty much matches up with my results.  Particularly like the 630 comparison to 1000w, never been a fan of 1000w HPS due to heat output and having to spread all that wattage from one central point, so to get a rough equivalent from 2 points spread apart a bit, with so much less heat and power costs sounds like a good thing.  Add in a light spectrum that's much closer to natural sunlight and it just gets better.  Also can't help thinking that if I'd run say a 600 and 400 HPS for a total of 1000w, I would have been pushing shit uphill to achieve the same yield I did with 630w CMH, though it should have gotten close.

 

On the heat front, I feel that, based on my limited understanding of physics, when you have energy producing light, any heat is wasted energy, and that's an area these have a big advantage over HPS.  Watt for watt they run cooler, so therefore that energy that would otherwise go to heat is now going into light production.  Maybe someone with better science understanding can tell me if I'm right or wrong?

 

I'll be getting a 3rd light and trying another run next year, and will be hoping the results will be what I expect, otherwise it will be money I can't afford to spend down the drain.  I'll let everyone know how it works out.  I might also bung one in my little veg tent one day for an auto grow to see how they compare to the 400w digi HPS I usually use in there.

[billygoat]

Great write up Sir.

 

Half way through I'm thinking to myself, buy a 3rd light, you answered that.

 

Only one criticism. A 5l V8 is an Aussie icon, not a yank tank, they typically have 400 cubes minimum. .

 

Never late in a 308 !

[Indycar]

Very helpful information, Sir Hashy.

 

What you posted there has answered a couple of questions that I have been curious about for some time, mainly about heat and bud density that's produced with the 315w CHM.

 

I'm a bit like yourself, where I like to do both indoor and outdoor growing. Indoors during winter and outdoors during the warmer months. But where I'm located the night temps can nosedive to low single digit numbers fairly quickly, and the temp output of 315w CHM wouldn't generate the heat I like to have in my cab which I like to have humming around the 22c-28c range. And because the 315w doesn't generate much more heat above ambient, it would probably give me a cab temp of around 10c during the middle of these winter nights (I run my light cycle at nights).

 

So, considering bud density and achievable cab temps, it's looking like I'll be sticking with my 600w for some time to come. Which is a bit of a bummer because I wanted to get my power usage down under 800 watts for the cab when it's running the day cycle. S'pose I can't complain too much as it usually runs a shade over 1000w with the 600w HPS.

 

Cheers

[phenix]

I've read lots of info lately about spectrums... perhaps you could have the best of both worlds by using the HPS for yield but switch or supplement with MH or other 10000K maybe even 14000K lighting (T5?) in the last couple weeks of flower. I've read that the HPS spectrum doesnt make the plant want to finish... all things I will be experimenting with in upcoming grows in my quest to find what makes the perfect medicine.

 

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