Ventilated Light Tube Question.

J

jekeke

Member
Hey,


I have a drier tube running from my window to my ventilated light tube then running out the other side to a fan. This draws cold air in from outside -10 to -30 celcius which keeps my light tube cold to touch. But this creates quite a bit of humidity inside the light tube where the cold air meets the heat from the bulb. Is this going to damage anything? Are there ways to decrease the humidity, such as running a longer drier tube around the room to warm up the cold air a little bit? Or should I just ventilate into a different room rather then outside and use a larger fan to compensate for the warmer air its pulling through, then at least their is no humidity being created.
 
TotalSnafu

TotalSnafu

Member
Sounds like overkill. You dont need to bring cold air IN...you need to send hot air OUT. Putting a sufficiently sized fan at one end of the light housing to direct hot air out of the room should be sufficient, and eliminate the risk of electrical shorts, bulb cracking, or even fire, from the water condensation. Keep it simple. Use the existing ducting, but move the fan to the end of the light housing. Connect the ducting to the fan. As long as the fan has some ooomph, itll suck the hot air out.
 
J

jekeke

Member
It's a 6" 110V muffin fan that runs at 40 watts. Has to put out at least 600-1000CFM, I tried running it that way first and it still got 30ish degree celcius 4-10" underneath the glass, which is where I want my plant too be, do you think throwing in a second fan somewhere in the line or purchasing a higher CFM fan all together will cool the light bulb better without running it outside? I like the fact that I can literally put the glass touching my plants without it affecting them currently, so would be nice to find some sort of dehumidifer I could add into the exhaust line somewhere to remove moisture. Just a thought, I don't disagree with just shooting the hot air out if I can get the tube to run a bit cooler. Its not the hot air that is the problem, it's the radiant heat from the bulb in general, but I guess cooling the bulb that much could cause cracking like you said. if I run the tube going out do you think that the air inside the tube will go cold enough to crack the bulb when it turns on after 12 hrs of darkness, should I put a trap to only let out and not in? Thanks for all your suggstions guys.
 
TotalSnafu

TotalSnafu

Member
Rapid fire round:
Dehumidifier- No. Wont suck all the moisture out of the air. Any moisture will condense, and if u do suck all the moisture out, sending arid air into your grow room will screw with your plants to no end. Moisture retains heat, and totally dry air will exacerbate your problem by fluctuating in temp wildly during light on/off cycles.

More powerful fan- YES. I know exactly what fan you are using, and its not gonna be enough to ventilate a cardboard box. You either need a bigger fan, or a more powerful fan (spins faster=high wattage). Walmart sells these black 8" 3-speed fans http://www.walmart.com/ip/Black-and-Decker-8-High-Velocity-Turbo-Fan/21097090. That, or something similar, should be plenty.
Just tape the duct to the fan to seal it.

Cooling bulb- This is unneccesary. The bulbs only work at extremely high temperatures- thats why the arc tube is encased in a glass housing (assuming you are using MH or HPS). You just need to get the hot air out.

Room temperature- if the aforementioned changes dont drop the air temp enough, then you need to bring cool (not cold!) air into the room. Air from an adjacent space would be preferrable, but you can draw air in from outside, too. Just make the air duct really small (2-4") if its -10C outside, and tinker with it until you get stable room temp. And make sure the cool air comes in at waist level or lower. It needs time to warm as it rises, otherwise you are dumping cold air onto plants.
 
J

jekeke

Member
TotalSnafu said:
Rapid fire round:
Dehumidifier- No. Wont suck all the moisture out of the air. Any moisture will condense, and if u do suck all the moisture out, sending arid air into your grow room will screw with your plants to no end. Moisture retains heat, and totally dry air will exacerbate your problem by fluctuating in temp wildly during light on/off cycles.

More powerful fan- YES. I know exactly what fan you are using, and its not gonna be enough to ventilate a cardboard box. You either need a bigger fan, or a more powerful fan (spins faster=high wattage). Walmart sells these black 8" 3-speed fans http://www.walmart.com/ip/Black-and-Decker-8-High-Velocity-Turbo-Fan/21097090. That, or something similar, should be plenty.
Just tape the duct to the fan to seal it.

Cooling bulb- This is unneccesary. The bulbs only work at extremely high temperatures- thats why the arc tube is encased in a glass housing (assuming you are using MH or HPS). You just need to get the hot air out.

Room temperature- if the aforementioned changes dont drop the air temp enough, then you need to bring cool (not cold!) air into the room. Air from an adjacent space would be preferrable, but you can draw air in from outside, too. Just make the air duct really small (2-4") if its -10C outside, and tinker with it until you get stable room temp. And make sure the cool air comes in at waist level or lower. It needs time to warm as it rises, otherwise you are dumping cold air onto plants.
Click to expand...


EDIT**
Looked it up, according to other AXIAL AC Fans that put out around 46-40 watts they are only putting 40-100 CFM! SO that must be the problem they just lied about their fan at the store. I'll have to grab myself a proper 300-500 CFM Inline Duct Fan and it should solve my problem, I'll let you guys know for future informational purposes on choosing fan sizes with ducting/lamp sizes. Any suggestions feel free to post! Thanks :)
 
jimithewop

jimithewop

Active Member
What watt light r u using? Here is my veg set up 600w turned down to 300w my 6 in inline keeps my light cool enough that i wont need to vent out of the grow space till i put my hps in at 600w20121203_055808.jpg
 
J

jekeke

Member
Busted two fan blades off and shortened my ventilation tubing quite a bit and seem to be getting the air movement I need with the Axial fan at 600 watt! :P added 1 3 speed 24" rotating fan to help move some air around and works great now. Will probably still throw two inline 300 CFM 6" fans in later though.
 
You must log in or register to reply here.
Top