PC Grow with A 250 Watt HPS!! Advice?

Hi there,

Currently gathering all the equipment to build my pc grow box. The pc case dimensions are 565mm (H) 545 (L) 210 (W) with 2 250mm extake 1 125m intake which makes me think I could get a 250 HPS cooltube in there with ballast outside the case.

Surely there isn't much difference between a 250watt envirolite and a 250 watt HPS cooltube? Any suggestions or criticism welcome!

the hps puts out more lumens, i would go with the HPS better buds dring flower cycle ( it has a great amount of the red spectrum )

ChaosSelling said:

the hps puts out more lumens, i would go with the HPS better buds dring flower cycle ( it has a great amount of the red spectrum )

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Thats why I wanted to use the HPS but i'm not too sure if it will make a big difference in temperature. The HPS isn't going to take anymore room up in the PC but I don't want it to send the temperatures through the roof. Anyone had any experiences with a HPS in a PC? I've seen 70watts done but not 250!!

I don't have any experience with cooltubes but is there enough airflow to keep that space cool? With only one 120mm intake and two 250mm (are these on the side of the case? Those are HUGE!) your airflow is not going to be balanced. With such a small space I would think you're going to need all the cooling (fresh air) you can get. My experience with air balancing in closed spaces tells me whatever is expelled should be replaced. With this setup you're going to be sucking air in passively through the cracks inefficiently retarding the airflow. Just my thoughts

CaNNaBiZ CaNucK said:

I don't have any experience with cooltubes but is there enough airflow to keep that space cool? With only one 120mm intake and two 250mm (are these on the side of the case? Those are HUGE!) your airflow is not going to be balanced. With such a small space I would think you're going to need all the cooling (fresh air) you can get. My experience with air balancing in closed spaces tells me whatever is expelled should be replaced. With this setup you're going to be sucking air in passively through the cracks inefficiently retarding the airflow. Just my thoughts

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Your probably right, I don't have the case yet so I can't look at it and wonder where I could mod the case to add more ventilation. I was would have to use a 125mm extake on the cooltube, then the 250mm are on the side of the case one for intake one for extake....THEY ARE HUGE!! I should be moving some air??

When I was a little bit more clear headed I posted this earlier

CaNNaBiZ CaNucK said:

You're cfm (cubic feet per minute) requirements depend on your grow space ultimately. Find the cubic area of your space and make sure that amount is exchanged every 1-5 times per minute (as a rule of thumb).

Say your area is (LxWxH) 5ftx5ftx5ft = 125 cubic feet. You need a fan with 125 cfm AT LEAST. In this case, you could use a fan with 125-625cfm. But remember, the higher the better ... as with many situations

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But keep in mind that with skyrocketing temps in a cramped grow space you could need even more airflow. I wouldn't worry too much about the cfms of a pc fan for a pc grow though. They usually are no less than 50cfm with 120mms.

Hope this helps

To elaborate I meant that pc fans easily displace and replace enough air for computing and CFL applications, NOT HPS. For such high wattage you will need IMO a very high cfm rating for your grow. But the only way to know is to try it!! KUDOS to you!!

Your grow space is less than 1sq foot (2 cubic feet), so no matter how much light you have it will be impossible to grow more than about 2oz dried bud in that space. A good-optimum grow yields about .5 - 1 gram of dried bud per watt of HID. If you do the math, you will see that a single 100w HID would be more light than your plants can actually use for that space. A 250w HID will just add unnecessary heat and force you to raise the light higher above the plants to keep from burning them (even with a cool tube) - thus using up more of your valuable limited vertical growing space.

I've been growing in a 2.25 square foot garden 18" x 18" with 24" of vertical grow space (grow space calculated after deducting the space eaten up by my hydro kit, the height of the light itself, and space between light and plant) with a single 150w HPS supplemented by a 78w CFL array. Later, I actually took out the CFL array and it did not lower my yield at all...thus indicating I am probably providing more light than I can use with the 150 HPS alone.

Think about it: my garden is probably 3x bigger than yours will be (in total cubic inches), and mine is getting more light than it can use with a single 150w HID.

Extra light is not a "problem", it is just wasted...but extra heat and less vertical growing space are both problems you could avoid with a smaller light.

I know everybody who grows likes to brag about how big their lights are, but especially for small grows like ours: more is not usually better - it can actually be worse.

Agree 100% with previous post. 100w HPS are readily available and will be much easier to control while providing far more than adequate light for a pc case. 75w are out there too, although I'm not sure of the quality of available bulbs.

One more note: My 150w HID increases the grow temp in my box by about 4-5 degrees even with good ventilation (probably because it is such a small enclosed space).

Out of curiosity and a desire to lower the temp in my cab during summer (it's fine in winter), I just bought a quad-band 90w UFO LED and want to see how it compares in performance to my 150w HPS, but it will be several weeks before I begin that test.

Shiitake, I dunno if you saw the thread on here with the 90w LED, there was a link in a recent thread, but it was freakin impressive. I'll try to remember which thread it was if you didnt. 108g yield.

Thanks for your response I

Thanks for your response I just wanted some advice from people who were already using HID lights in a small space which is what I want to do. In the UK it seems to be difficult to get hold of a 100w HPS or 70w for that matter. I think most people do security light conversions for which I have seen an FAQ on here.
If I went with a 250watt envirolite or a 125watt envirolite would I be able to yield anywhere near 25+ gram of dried bud? I'm not too sure about them I've had bad experiences in the past with low yields and I wanted to do a HPS this time but for the next 3-4 months a PC Grow is my only option.

Unless you have a very fast moving air flow through your cooltube you will roast your ladies, in a grow area of that size, generally HPS(250w) and above are for closet sized growrooms or bigger, in a case that size I would say going the HPS route would be a fire hazzard, a 125/150watt set of blue n red spec envirolights will be more than enough in your room, I'd still use the cooltube with them .. although the HPS is a shitload hotter whilst on than the enviro's, the enviro's get warm and will still burn the tops of your plants if airflow and temp aren't taken into consideration, you can now get 250w and 300w envirolites but would be careful because heat builds up in small places. i started with a 150w envirolite in a modified kitchen cupboard and the 150 because of the size stayed cool with a small 120mm fan at the bottom pulling air in and another 120mm sucking air out at the top, I mounted the top fan 100mm below the highest height of the light so it would suck all the hot/warm air straight out. if possible get a cupboard no smaller than a 1 meter in height, and no less than half a meter squared, the plants will double in size and then some once put into flower, so unless your growing lowryder strains i doubt you'll get more than a Q off your infant sized plants, i once looked into the whole PC op. but you ll only set yourself up for misery, youll kick yourself cos you could ve been over halfway towards at least an oz n a half, my mate had one it looked good, it had everything you need but......BUT.. cos of the limited height for growing it didnt have enough room or air-flow and it died DO YOURSELF A FAVOUR.. you can use the PC for vegging but you need a cupboard 2-3 times bigger if you want any kind of bud quantity, or bud at all!!! hope this helps, hope all goes well anyway let us know what happens, regards STELTHY

PS LOOK AT MY PICS I DID A TWIN 90W UFO LED + 150W ENVIRO GROW, GOT A FEW GOOD PICS UP, AM JUST ABOUT TO PUT INTO FLOWER GOT LOTS OF BIG BIG PLANT PICS TO ADD, BUT MY COMPUTER IS BEING GAY AND WONT LET ME UPLOAD THEM YET, ILL KEEP HOLD OF THEM AND ADD THEM ASAP I THINK MYSET-UP HAS WORKED REALLY F**KIN WELL LET ME HEAR YOUR THOUGHT TB WHEN YA CAN ~ STELTHY

I've tried a few setups in the pc and 250w is too much either for cfl or hps.
A 125w red enviro with a 12w additional 6500k ran fine and was maybe 5F hotter than room temps.
I upped this to 150w + 12w but used an external ballasted nlite and these emit much more light than self ballasted bulbs. The 150 + 12 ran cooler than the 125 + 12 but there was so much light it bleached the plants.
I'm using 100w mh now and it seems about right.

For info you want around 9500 lumens of light MAXIMUM in 1 sq ft of space. To work out the wattage of the bulbs you can use the following as a rough guide:

cfl with external ballast = 70 lumens / watt
cfl self ballasted = 50 lumens / watt
mh with external ballast = 100 lumens / watt
hps with external ballast = 105 lumens / watt
Just divide 9500 lumens by any of the numbers above to find out how many watts you should be aiming for to get the best buds possible.

Those twin 250mm fans should cool down whatever you put in there, but don't forget that you will need to lightproof both of them completely or your plants won't flower.

StealthHawk said:

Hi there,

Currently gathering all the equipment to build my pc grow box. The pc case dimensions are 565mm (H) 545 (L) 210 (W) with 2 250mm extake 1 125m intake which makes me think I could get a 250 HPS cooltube in there with ballast outside the case.

Surely there isn't much difference between a 250watt envirolite and a 250 watt HPS cooltube? Any suggestions or criticism welcome!

Click to expand...

A real man would find a way to run two 1Ks on light movers in that computer

But what the guy said about not needing the 250 - he's correct; will be more problems then it's worth.

5 inches for cooltube, and plants 5 inches from light.. thats 10 inches plus pot size.. your pplant would be too short and defete the purpose of the extra light..

bca21 said:

5 inches for cooltube, and plants 5 inches from light.. thats 10 inches plus pot size.. your pplant would be too short and defete the purpose of the extra light..

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Thanks for your input it's appreciated. I'm just going to use a red 125watt envirolite and LST the plant.

Any idea's how you make fan's lightproof i can't seem to find much info on it?

it won't work, too hot

you could put a bulkhead between the fan and lights, or make a small duct for the fan with a bend in it. Check out some DIY carbon filters and get creative using the carbon to block the light.