Debating Grow Tent Size & If I should go CFM Overkill

[BadlyDrawnBoy]

Thanks to some suggestions here on the forum, I'm going to get a tent and do it proper with an exhaust system.

The tent I had considered originally, before ditching the idea completely, was one 48x24x60.

I'm not looking to grow more than 2 or 3 plants at a time, however I'm considering the option to be able to grow more (and vegetables/tomatoes at a later time) would be nice, and perhaps I should step up the tent size a bit more. Space isn't an issue, so I could go as large as I wanted in tent size.

A 4" inline fan would be fine for the originally stated tent dimensions. However, I'm wondering if you all have found that after purchasing and using your fans, you began to wish you had more power and wished you'd gone to a larger size. The 4" to the 6" jumps up from 190 to 442 cfm, so it's pretty substantial just for a 2" upgrade, and only about $20 in price.

I'm going to get a carbon filter also. The light I'm getting is an LED, so heat won't be too big an issue. The duct exiting the tent will travel only about 5 feet to the window.

I'll buy a fan speed dial, so I could run it low (especially if it's the 6" 442 cfm).

Can it be a negative to have more cfm power than you need?

Thanks for any help

 

[MonkeyPickAss]

i mean if you dont want a 4x2 then i guess your option is a 4x4. 6" vivosun fan and a 6" ipower carbon filter. Done and done.

 

[BadlyDrawnBoy]

i mean if you dont want a 4x2 then i guess your option is a 4x4. 6" vivosun fan and a 6" ipower carbon filter. Done and done.

I'm feeling the 4x2. More space means I'd need stronger lighting too, which I'm not prepared to invest in at the moment. I think I'll do the 4x2. the 4" fan should be plenty for that

 

[MonkeyPickAss]

What light are you thinking? Currently in my 4x2 I have 4 300w vipars.

 

[BadlyDrawnBoy]

What light are you thinking? Currently in my 4x2 I have 4 300w vipars.

Those are led?

So far I've decided on the galaxy hydro 300 watt led 16 inch light. But I'm going to give it a day or two to let my mind change lol. I actually have a 1000w hps from almost 15 years ago, but honestly I'm frightened to use it, as I'm not sure of it's overall condition anymore. I don't want to burn anything down. That would be overkill, anyway.

I'll get two of the lights. Only planning on doing 2 plants to start. Might fill in the bottom areas with some CFLs I have, but not sure. That was why I was considering getting a bigger size tent, because I like the idea of filling in the lower plant areas, that don't get a lot of top light, with cfls. I still can with a smaller tent, since they can be so close to the plant. It'll just be tighter.

 

[MonkeyPickAss]

2 plants with 1 300w galaxy hydro is going to be pretty disappointing. 1 300w per plant is a pretty good rule.

 

[OldMedUser]

I'd go with the 4x4 at least. Don't have to fill the whole tent and can rig up something white to act as the fourth wall and just use half the tent for growing for now then have room for expansion later if the mood should strike you and I bet it will.

And get the 6" fan for sure. Then you can run it at a much lower speed, use less power and be a lot quieter. A 4" would be screaming all the time. A temp/RH controller is very useful to maintain a steady temp and humidity in the tent and they don't cost much. Have to remember that the filter will cut the airflow as much as half. An 8" filter attached to a 6" fan will give better flow and last longer too before it stops holding the stink back.

I'm using a 20 year old 1000W MH now and it works fine. Would kick ass in a 4x4 full of greenery. I'm using a 940W Hortilux conversion bulb in it for flowering. I should be chopping some right now but I'll get to it soon.

 

[BadlyDrawnBoy]

2 plants with 1 300w galaxy hydro is going to be pretty disappointing. 1 300w per plant is a pretty good rule.

Yeah I'm planning on getting two lights, one per plant.

I'd go with the 4x4 at least. Don't have to fill the whole tent and can rig up something white to act as the fourth wall and just use half the tent for growing for now then have room for expansion later if the mood should strike you and I bet it will.

And get the 6" fan for sure. Then you can run it at a much lower speed, use less power and be a lot quieter. A 4" would be screaming all the time. A temp/RH controller is very useful to maintain a steady temp and humidity in the tent and they don't cost much. Have to remember that the filter will cut the airflow as much as half. An 8" filter attached to a 6" fan will give better flow and last longer too before it stops holding the stink back.

I'm using a 20 year old 1000W MH now and it works fine. Would kick ass in a 4x4 full of greenery. I'm using a 940W Hortilux conversion bulb in it for flowering. I should be chopping some right now but I'll get to it soon.

Oh I didn't realize you could fit an 8" filter on a smaller fan. I'll consider that then.

So the 4" fan doesn't have the ability to hook to a fan speed adjuster? I wouldn't be able to run the 4" at a low speed?

Man If I could use that 1000w hps and feel safe doing it, that'd be great. could save $200 not having to buy new lights. But the ballast has been sitting in a room that gets really warm in the summer and really cold in the winter. You think this would affect the condition of the ballast at all? I'd still have to replace the bulb i think, it looks pretty aged. I'm just really concerned about starting fires and having excessive heat issues. I'm not needing a massive yield, I smoke very little and vaporize, a little goes a long way. That's why I'm only doing 2 plants, 2 different strains. One for nighttime insomnia, the other for exciting the day

It would also destroy the electricity bill having that 1000w hps going. I'd probably surpass the $200 i spent on leds in no time just on the added cost of electric with the hps.

 

[BadlyDrawnBoy]

A 4" would be screaming all the time.

Oh, do you mean because the 4" fan wouldn't be sufficient to filter the space of a 4x2 tent? Yeah if the filter doubles the cfm useage, then i'd be looking at about 80 cfm's free. should be alright for a 4x2 tent. i'll just go with the 6". was just concerned it would "suck too hard"

 

[OldMedUser]

Oh I didn't realize you could fit an 8" filter on a smaller fan. I'll consider that then.

You can buy adaptors to step down the sizes to fit. Most building supply stores or heat and A/C shops will have them if not hydro stores. Not a lot of money either.

Oh, do you mean because the 4" fan wouldn't be sufficient to filter the space of a 4x2 tent? Yeah if the filter doubles the cfm useage, then i'd be looking at about 80 cfm's free. should be alright for a 4x2 tent. i'll just go with the 6". was just concerned it would "suck too hard"

Exactly. Harder on the fan trying to pull through the filter too. You'll be able to run a 6" at half speed and still move more air. And it'll suck just how you like it.

Hook up the 1000 and see if it even fires the bulb you have. An older 1000W would still kick ass. I still use a 16 yo old Hortilux bulb on a 30 yo ballast and the plants grow great with it. Still can't believe it works at all.

With our power at $0.22/kwh it's costing me almost $90/mth for the 1000W on 12/12. Got the 400 in the spare bedroom doing 18/6 duty for another $50/mth. All the other stuff like the light mover, oscillating fans, exhaust fan etc probably tack on another $20.

Got 27 plants of various sizes to start cropping any day now so that makes me feel better.

 

[AliCakes]

1000w HPS is way too much for a 2x4x5 tent. But it will hold 2-3 plants nicely. Cropping through veg will be necessary though. 5' is not a lot of headspace. I just jumped up to a 4x4 Gorilla grow tent. My last tent was an Amazon tent in this exact size. If you have the room, I would move up to a 3x3x7-8. The headspace is a way bigger deal than the footprint.

 

[BadlyDrawnBoy]

1000w HPS is way too much for a 2x4x5 tent. But it will hold 2-3 plants nicely. Cropping through veg will be necessary though. 5' is not a lot of headspace. I just jumped up to a 4x4 Gorilla grow tent. My last tent was an Amazon tent in this exact size. If you have the room, I would move up to a 3x3x7-8. The headspace is a way bigger deal than the footprint.

You're right, I'd like the tent to at least allow me to step into it and stand straight. I don't want to be worried about running out of height for the plants and having the lights too close. Also, I'd like to grow tomatoes in here as well, and they can get quite high.

I see a tent with good reviews, dimensions 39x39x78. That would be much better.

I'll have to figure out if 2 - 300 watt led lights would fill that size tent properly. I can fill some cfl's in there temporarily if I have to.

 

[coreywebster]

Most fires in grow rooms start because the male and females on the ballasts are not connected properly which causes arcing which melts the plastic and sets fire to near by fabrics, or from normal household plugs not been plugged right in, same thing happens.
Anyway, that's beside the point if your not going to use a 1000w hps.

Get the 3x3(39x39), the height is better, it will be easier to cool, you don't have to use every inch and its nice to be able to get in there and be up close and personal with your plants. Plus you can sit in there with the filter running when it comes to harvest day.

If you do get bigger fans and filters and want to turn them down buy a viable transformer type of speed controller, cheap speed controllers cause a hum that can be heard at night when nothing is stirring, not even a mouse.

 

[OldMedUser]

I made my own speed control with a ceiling fan controller. It's plugged in to my heat/RH controller and keeps the temps nice and steady where I set it. Bathroom fan RH thermostat thingy and a cooling thermostat. I bought the parts to make a 2nd one. I put a meter on the fan with the speed control hooked up and it maxs out at 120W so I dialed it down to 60W and put a little mark on the dial. Works great at that speed and the fan is a lot quieter and runs smoothly. Little slow as it starts up tho but only a few seconds.



They should make those tents 50" so a 4' bank of T-5s would have a bit of room.

 

[Roger A. Shrubber]

i run a 4x4 tent for flower, and to really control the smell, i've had to upgrade to the 550 cfm fresh filter hooked to a 440 cfm fan. heat wasn't really an issue, the 4 inch fans pulls enough air, but the 4 inch filter couldn't handle the smell.
https://www.amazon.com/Phresh-Filter-24-550-CFM/dp/B0032JULLY/ref=sr_1_1?ie=UTF8&qid=1496840354&sr=8-1&keywords=phresh+filter+550+cfm&th=1
went to that, no smell anymore, and can run my fan at half speed

 

[BadlyDrawnBoy]

i run a 4x4 tent for flower, and to really control the smell, i've had to upgrade to the 550 cfm fresh filter hooked to a 440 cfm fan. heat wasn't really an issue, the 4 inch fans pulls enough air, but the 4 inch filter couldn't handle the smell.
https://www.amazon.com/Phresh-Filter-24-550-CFM/dp/B0032JULLY/ref=sr_1_1?ie=UTF8&qid=1496840354&sr=8-1&keywords=phresh+filter+550+cfm&th=1
went to that, no smell anymore, and can run my fan at half speed

I was going to get the 4", but I'm going 6" now, after others have shared how helpful it is having a higher power fan. Makes sense, I can run it at the lowest speed, rather than needing to have the 4" full power all the time. Will likely help with sound too, since I can have the 6" at low power.

Most fires in grow rooms start because the male and females on the ballasts are not connected properly which causes arcing which melts the plastic and sets fire to near by fabrics, or from normal household plugs not been plugged right in, same thing happens.
Anyway, that's beside the point if your not going to use a 100w hps.

Get the 3x3(39x39), the height is better, it will be easier to cool, you don't have to use every inch and its nice to be able to get in there and be up close and personal with your plants. Plus you can sit in there with the filter running when it comes to harvest day.

If you do get bigger fans and filters and want to turn them down buy a viable transformer type of speed controller, cheap speed controllers cause a hum that can be heard at night when nothing is stirring, not even a mouse.

I'll be purchasing a speed controller with the fan for sure.

Yeah I'm more into the cooler running lights. I don't like that gut fear feeling every time you walk out of the room with a hps light going, afraid it might burn down your home.

I was concerned about the extra space in the tent, having it a foot higher, that the lights wouldn't cover the new added area, but really there isn't more area to fill for the lights, because i can simply drop the lights down lower to the plants and the space above the light is just potential space to be filled when the plants are bigger. Should be perfect size tent for 2 - 300 watt led lights.

 

[MonkeyPickAss]

I hope you understand how large a 6" fan and filter are. They will overwhelm a 4x2 tent. I see you are looking at 39x39 so nvm lol.

 

[McStrats]

CFM x 60 / area or 190 x 60 = 11,400 / 40 = 285 ach

So...a 4" fan that does 190 cfm gives you 285 air changes per hr in a 40 cu ft tent - but you only really need 10 ach per hr for cannabis *that is your sweet spot - more air than that doesn't really do anything but make a lot of noise...it is also too many cfm for carbon filtration to be effective. Carbon needs "dwell time" - pulling too quickly through the carbon means that you will have odor issues.

 

[BadlyDrawnBoy]

I hope you understand how large a 6" fan and filter are. They will overwhelm a 4x2 tent. I see you are looking at 39x39 so nvm lol.

CFM x 60 / area or 190 x 60 = 11,400 / 40 = 285 ach

So...a 4" fan that does 190 cfm gives you 285 air changes per hr in a 40 cu ft tent - but you only really need 10 ach per hr for cannabis *that is your sweet spot - more air than that doesn't really do anything but make a lot of noise...it is also too many cfm for carbon filtration to be effective. Carbon needs "dwell time" - pulling too quickly through the carbon means that you will have odor issues.

Do you guys think I should go with the 4" 190cfm fan for a 39x39x78 tent? It is much cheaper getting a 4" fan and filter, which is desirable, but I thought I could work the fan less by having a 6" and having it turned down low, instead of having a 4" turned at high 24/7.

It seems like the 4" would be plenty efficient for this size tent...I just don't want to underwhelm things. I'd rather buy right the first time and do everything proper from the beginning, that's why i was leaning towards the 6".

Again, I'm using led's, so heat from the lamps shouldn't be much of an issue. I will have a carbon filter attached

 

[SouthCross]

I have a 2x4x6 and use an 8". It's on its lowest speed and the sides of the tent suck in. All three 6"x14" vents are open. The fan has an 8" elbow to a 6x8" reducer. 6" duct going to the tent with another 6x8 reducer to fit a 8" port. Carbon filter on the exhaust side.

I went overkill because it cannot stink. There's zero option for smell. A 6" would work fine but I'd have to run it faster then half speed. A 4" would be too small on full blast.

With a room temperature of 75°f, the plants run 2-3° cooler. As I type they're 72°. Zero smell unless you open the tent.