Is a 400 watt light too much for a 48x24x60 tent?

VACAVILLE,CA.GROWER · Mar 2, 2015

I am about to start a small grow. I have a 48x24x60 tent. I was thinking of buying a 400 watt mh/hps light. Would 400 watts be too much for this size tent?

nomofatum · Mar 2, 2015

400w should be fine in that space. 400w HPS puts out 50,000 lumens, or about 6250 lumens per sqft. 5000-7500 lumens per sqft is where you want to be. That leaves you with up to 10,000 lumens worth of lighting you can supplement with if you wish. Look at 10% UVB (reptile) bulbs (no more than 40w for your space, UVB can burn if you go overboard) and 6500k to supplement the HPS.

Note the 400w version of HPS isn't very efficient, you will have to worry about heat...

indicat33 · Mar 2, 2015

My 400w HPS boasts 55,000 Initial Lumens. I use it in my 2x3' space. Damn that sob is Bright !!!

~ I really don't see how people run 600 or 1K watters! 8-)

VACAVILLE,CA.GROWER · Mar 2, 2015

nomofatum said:
400w should be fine in that space. 400w HPS puts out 50,000 lumens, or about 6250 lumens per sqft. 5000-7500 lumens per sqft is where you want to be. That leaves you with up to 10,000 lumens worth of lighting you can supplement with if you wish. Look at 10% UVB (reptile) bulbs (no more than 40w for your space, UVB can burn if you go overboard) and 6500k to supplement the HPS.

Note the 400w version of HPS isn't very efficient, you will have to worry about heat...

what does the uvb bulbs do for a plant?

nomofatum · Mar 2, 2015

VACAVILLE said:
what does the uvb bulbs do for a plant?

UVB stimulates resin production. THC/resin is effectively sunscreen for the plant, expose to more UVB and the plant will produce more sunscreen/resin/THC.

This is the reason that the most potent original strains were from places on earth with a high UVB exposure, like the Hindu Kush Mountains.

VACAVILLE,CA.GROWER · Mar 2, 2015

nomofatum said:
UVB stimulates resin production. THC/resin is effectively sunscreen for the plant, expose to more UVB and the plant will produce more sunscreen/resin/THC.

This is the reason that the most potent original strains were from places on earth with a high UVB exposure, like the Hindu Kush Mountains.

Thank you for the reply. So witha 400 watt light in that size tent. How many uvb bulbs would someone use. Also would a 400 watt light work in a 36x20x60 tent or would that be too hot?

greenghost420 · Mar 2, 2015

aim for 50+ per sqft, 400/ 4ft x 2 ft= 50 per.. 400/ 3x1.5= bout 90 something

nomofatum · Mar 2, 2015

VACAVILLE said:
Thank you for the reply. So witha 400 watt light in that size tent. How many uvb bulbs would someone use. Also would a 400 watt light work in a 36x20x60 tent or would that be too hot?

Heat can be an issue in any tent size, you need venting for that. You also need venting for humidity issues.

400w in 5 sqft (36x20) = 10,000 lumens per sqft, you will likely fry them without adding CO2 and humidity control at those levels.

UVB 10% bulbs should be between 3w and 5w per sqft. Any more and you will fry them. Do the math and figure out sqft for your tent size. 5000-7500 lumens per sqft and 3-5w per sqft of UVB (assume 100 lumens per watt for the UVB bulbs.) That is your target for total lighting levels. You can get much more detailed and precise with other measures, but this will get you to a good and survivable range.

Rich_Porter1 · Mar 2, 2015

nomofatum said:
400w should be fine in that space. 400w HPS puts out 50,000 lumens, or about 6250 lumens per sqft. 5000-7500 lumens per sqft is where you want to be. That leaves you with up to 10,000 lumens worth of lighting you can supplement with if you wish. Look at 10% UVB (reptile) bulbs (no more than 40w for your space, UVB can burn if you go overboard) and 6500k to supplement the HPS.

Note the 400w version of HPS isn't very efficient, you will have to worry about heat...

great bit of info there! im getting a grow tent 120 cm width 120 cm depth and 200cm height with a 400w HPS light..whats your take on this? and what sort of UVB light do oyou recommend?

thanks :-)

nomofatum · Mar 2, 2015

Rich_Porter1 said:
great bit of info there! im getting a grow tent 120 cm width 120 cm depth and 200cm height with a 400w HPS light..whats your take on this? and what sort of UVB light do oyou recommend?

thanks

Skip the 400w. 600w is way more efficient and nearly twice as powerful in light output. (50,000 lumens vs 92,000 lumens) 92,000 / 16 sqft (4x4 tent, should be same as 120 cm tent) = 5750 lumens per sqft. Leaving you with 1750 lumens per sqft to go before hitting max. Or about 300w of supplemental lighting. 80w max UVB 10% reptile bulbs. The rest 6500k. If you switch to MH during veg you can also switch to 2700-3500k bulbs to supplement.

indicat33 · Mar 2, 2015

Rich_Porter1 said:
great bit of info there! im getting a grow tent 120 cm width 120 cm depth and 200cm height with a 400w HPS light..whats your take on this? and what sort of UVB light do oyou recommend?

thanks

If your ballast is switchable, you could go with a 400w MH Lamp. You can find Specialized, FAR blue-violet spectrum bulbs on amazon / e-bay. Imagine, a blue-violet BLAST on your plants, entire flowering. The buds will be tight, compact, and Likely contain more resin than under hps. I am going to conduct this experiment in the near future, as I've heard many people who tried this, say they will never go back to hps -period. Worth a closer look, Imo :idea:

VACAVILLE,CA.GROWER · Mar 2, 2015

nomofatum said:
Heat can be an issue in any tent size, you need venting for that. You also need venting for humidity issues.

400w in 5 sqft (36x20) = 10,000 lumens per sqft, you will likely fry them without adding CO2 and humidity control at those levels.

UVB 10% bulbs should be between 3w and 5w per sqft. Any more and you will fry them. Do the math and figure out sqft for your tent size. 5000-7500 lumens per sqft and 3-5w per sqft of UVB (assume 100 lumens per watt for the UVB bulbs.) That is your target for total lighting levels. You can get much more detailed and precise with other measures, but this will get you to a good and survivable range.

ok I plan on using a 48x24x60 tent. I will be using a 400 watt mh/hps with just a wing reflector. I was planning on using a 4inch inline fan with filter. would this setup up work or is the fan too small?

nomofatum · Mar 2, 2015

VACAVILLE said:
ok I plan on using a 48x24x60 tent. I will be using a 400 watt mh/hps with just a wing reflector. I was planning on using a 4inch inline fan with filter. would this setup up work or is the fan too small?

A good 4" inline fan will clear enough air for that space easily. Just make sure you have a enough intakes open and good airflow to intakes.

Rich_Porter1 · Mar 2, 2015

nomofatum said:
Skip the 400w. 600w is way more efficient and nearly twice as powerful in light output. (50,000 lumens vs 92,000 lumens) 92,000 / 16 sqft (4x4 tent, should be same as 120 cm tent) = 5750 lumens per sqft. Leaving you with 1750 lumens per sqft to go before hitting max. Or about 300w of supplemental lighting. 80w max UVB 10% reptile bulbs. The rest 6500k. If you switch to MH during veg you can also switch to 2700-3500k bulbs to supplement.

thanks for your response, the only reason why i am getting a 400w is because this is what is included in the complete grow kit i am buying from ebay

VACAVILLE,CA.GROWER · Mar 2, 2015

nomofatum said:
A good 4" inline fan will clear enough air for that space easily. Just make sure you have a enough intakes open and good airflow to intakes.

ok thank you for your replies. Would it be a good idea to maybe add a 4 inch duct booster fan at the bottom of the tent too add air intake or just leave all the tent intake vents open. Again thank you for your time and replies.

nomofatum · Mar 2, 2015

Rich_Porter1 said:
thanks for your response, the only reason why i am getting a 400w is because this is what is included in the complete grow kit i am buying from ebay

I would use it for something else and get a 600w in there. Use it for a smaller veg space or for the vegi garden seed starting.

Rich_Porter1 · Mar 2, 2015

indicat33 said:
If your ballast is switchable, you could go with a 400w MH Lamp. You can find Specialized, FAR blue-violet spectrum bulbs on amazon / e-bay. Imagine, a blue-violet BLAST on your plants, entire flowering. The buds will be tight, compact, and Likely contain more resin than under hps. I am going to conduct this experiment in the near future, as I've heard many people who tried this, say they will never go back to hps -period. Worth a closer look, Imo

thanks for your message, the only reason i am using a 400w is because it comes with my complete grow kit, could you provide a link of what one of these MH lamps look like? i may give it a go later on :-)

nomofatum · Mar 2, 2015

VACAVILLE said:
ok thank you for your replies. Would it be a good idea to maybe add a 4 inch duct booster fan at the bottom of the tent too add air intake or just leave all the tent intake vents open. Again thank you for your time and replies.

I wouldn't put a fan on the intake. Better to just leave intake passive. By just exhausting you will pull air in any leaks with the negative pressure created. Adding an intake fan of the same size as your exhaust would actually create positive pressure (do to the resistance of the filter/ducting on the exhaust.) The result would be air leaking out every leak instead of leaking in, this in turn means the smell can escape. If you want to add an intake fan, make sure it is significantly smaller than your exhaust fan.

Rich_Porter1 · Mar 2, 2015

nomofatum said:
I would use it for something else and get a 600w in there. Use it for a smaller veg space or for the vegi garden seed starting.

thanks, i will most certainly look into this. can you just confirm whether i can use HPS lights for both Veg and Flowering stages?

VACAVILLE,CA.GROWER · Mar 2, 2015

nomofatum said:
I wouldn't put a fan on the intake. Better to just leave intake passive. By just exhausting you will pull air in any leaks with the negative pressure created. Adding an intake fan of the same size as your exhaust would actually create positive pressure (do to the resistance of the filter/ducting on the exhaust.) The result would be air leaking out every leak instead of leaking in, this in turn means the smell can escape. If you want to add an intake fan, make sure it is significantly smaller than your exhaust fan.

ok sounds great. Thank you for all your help.

Is a 400 watt light too much for a 48x24x60 tent?

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