Tent over spec'd but not cooling SOS

[neville hz]

Hi

Could do with some advice on what to do with my annoying HOT tent that I just cant get to cool unless I turn the lights right down to 250 watts.

Tent Size is a 2.4 x 2.0 x 1.2.
To work out what fans I needed i followed this calculation -
2.4x2.0x1.2 x 60 = 345m3

Fans I have are an 8" outlet (200mm 8"RVK200 A1 Extractor Fan - 796m3/hour) with CAN filter (CAN350 - 713m3) and a 6" inlet (150mm 6"RVK150 A1 Extractor Fan - 430m3/hour) drawing air from outside. Temps outside are 15 degrees.

I'm running two 600w lamps and the temps in the tent are 29 degrees C! With the outside temps at 18 the tent temp goes to 30/31.

I've tested the thermostat by plugging the fans both directly into the mains. It made no difference, they both ran at full speed and the temps stayed the same.

There arent any blockages in the ducting, both have a good flow with only slight bends.

The carbon filter is only 3 months old.

What to do? test next???


Thanks for any advice

 

[soundman]

Did you remove filter and see what happens? Strange situation.

Where do you vent the lights to? Do you have a lung room? A drawing may help?

 

[neville hz]

Hi soundman

I haven't removed it yet no. Id expect to feel a big increase in air flow out the ducting if I did that but whether that confirms the fan or filter is to blame im not sure.

I dont vent the lights. They are just 600watts with normal shades...no air cooled shades.
Not sure what a lung room is.

Its a tent within a room. Room temps outside the tent are about 20 degrees C. All tent vents and holes are closed so only air going into it is from the inlet fan.

 

[Old Toker]

If your exhaust fan and filter are both working correctly....and they probably are....then I don't think you are getting enough cool air into the tent from the intake. With lights on.... open all the intakes and the door and see if the temps drop. If they do then you might want to increase your air intake. I'd go with a couple of 8" passive vents. Two 8" vents will still provide negative pressure. JMPO....

BTW - a tent in a room = the room is the lung room

 

[Bush Dr]

Your basic calculation is wrong, you need 2 preferably 3 air changes per minute

 

[neville hz]

If your exhaust fan and filter are both working correctly....and they probably are....then I don't think you are getting enough cool air into the tent from the intake. With lights on.... open all the intakes and the door and see if the temps drop. If they do then you might want to increase your air intake. I'd go with a couple of 8" passive vents. Two 8" vents will still provide negative pressure. JMPO....

BTW - a tent in a room = the room is the lung room

Thanks Old Toker - I'd not heard of the term lung room before!

I've not been able to test out the tent intakes with the door open yet...I've opened the intakes along with the inlet fan on though.
The is air coming in from around the door with it closed as its not a very well fitting door/frame.

Temps outside are 15C, lights at 600w and temps in the tent are 27. The tent is being drawn in though, guessing there is a lot less negative pressure with the vents open too.

 

[neville hz]

Your basic calculation is wrong, you need 2 preferably 3 air changes per minute

Thanks Dr Bush

Can you tell me the calculation I need to use to work out how to do that?

 

[soundman]

Hi soundman

I haven't removed it yet no. Id expect to feel a big increase in air flow out the ducting if I did that but whether that confirms the fan or filter is to blame im not sure.

I dont vent the lights. They are just 600watts with normal shades...no air cooled shades.
Not sure what a lung room is.

Its a tent within a room. Room temps outside the tent are about 20 degrees C. All tent vents and holes are closed so only air going into it is from the inlet fan.

I am trying to get an idea of the size of your tent in feet. I don;t know what is width length and height. It seems small to me for two 600's without air cooled hoods. I grow in a 5 foot by 5 foot tent with air cooled hoods and it is hard to cool in that space.

More passive intake as mentioned is needed too.

 

[Old Toker]

I am assuming that your tent is long (7 1/2 ft) and narrow (4 ft) with a 6 1/2 ft ceiling - 202 cu ft. Granted two 600w lights is going to generate some heat in that smaller space....but if you have enough 20c (68f) or cooler air flowing through it.....you should be able to get the temps inside (lights on) under 80f (27c)....which is where you want them....right?
Is your 6" intake ducted through 6" ducting to outside of your house or is it drawing in 15c (60f) air from your lung room?

 

[Speed of green]

you shouldnt need an intake fan, as long as your exhaust fan is moving the air its rated at you should have 2x exchanges per minute.

is your tent sucked in tight with negative pressure? you may need another passive intake to deal with the volume of air you are trying to exhaust.

post some pictures if you can.

 

[Old Toker]

you shouldnt need an intake fan, as long as your exhaust fan is moving the air its rated at you should have 2x exchanges per minute.

is your tent sucked in tight with negative pressure? you may need another passive intake to deal with the volume of air you are trying to exhaust.

X2

 

[neville hz]

I did some tests tonight..hopefully they will answer your questions and help find a solution.

The temps outside are 17 C tonight.

With 2 lights on 600w
Lung room door CLOSED
Tent vents CLOSED
Inlet fan ON
Negative Pressure/Tent Sucked in YES
Temps in tent 29

With 2 lights on 600w
Lung room door OPEN
Tent vents OPEN
Inlet fan OFF
Negative Pressure/Tent Sucked in YES
Temps in tent 30

With 2 lights on 600w
Lung room door OPEN
Tent vents OPEN
Inlet fan ON
Negative Pressure/Tent Sucked in NO
Temps in tent 28

With 2 lights on 400w
Lung room door CLOSED
Tent vents CLOSED
Inlet fan ON
Negative pressure/Tent Sucked in YES
Temps in tent 27

For each time I made a change I left the tent for approx 15 mins before reading the temps.

 

[neville hz]

I am assuming that your tent is long (7 1/2 ft) and narrow (4 ft) with a 6 1/2 ft ceiling - 202 cu ft. Granted two 600w lights is going to generate some heat in that smaller space....but if you have enough 20c (68f) or cooler air flowing through it.....you should be able to get the temps inside (lights on) under 80f (27c)....which is where you want them....right?
Is your 6" intake ducted through 6" ducting to outside of your house or is it drawing in 15c (60f) air from your lung room?

25 - 27 degrees Id be much more comfortable with.
The 6" ducting is coming in from outside the house yep...currently drawing in 17 degrees C air.

 

[Old Toker]

......replaced post.

 

[Old Toker]

The 6" ducting is coming in from outside the house yep...currently drawing in 17 degrees C air.

Currently drawing 17C air from outside the house through a 6" vent directly into the tent....or into the lung room? Are you exhausting the air from inside the tent into the lung room or outside the house? What is the lung room temp?
Sorry about all the questions....but clearly I'm missing something.

 

[neville hz]

Currently drawing 17C air from outside the house through a 6" vent directly into the tent....or into the lung room? Are you exhausting the air from inside the tent into the lung room or outside the house? What is the lung room temp?
Sorry about all the questions....but clearly I'm missing something.

Hi Old Toker

Air is being drawn in from outside the house and the hot air is being exhausted outside of the house. No air from the lung room is being used to cool the tent...its just the room the tents in/nutes/storage.

The lung room temps will be whatever house temps are although, when the tent is going to 30 degrees the lung room is also pretty warm.

Btw Im not sure if using the term lung room is right in my setup as Im not using the room the tents in to breathe air to/from.

 

[Old Toker]

OK....now I understand. You are correct....the way you are using the room the tent is in....it is not a lung room....it's just a room that the tent is in.

How big is the room the tent is in? Are you able to seal it off from the rest of the house (not necessary....but helpful)?
Generally people draw air into their tent from the Lung Room. You adjust the temp/humidity of the air into the lung room and then you use that air to cool your tent. If the temp of the air going into the tent is low enough.....then it's just a matter of opening enough vents into the tent to get the air flow necessary to keep temps where you want them. I think the 6" intake vent from outside is not providing enough air flow into the tent to keep your temps down.

Is it possible to have that intake send the nice cold air into your lung room and cool THAT room under 70f (20c)? If so then you can just open as many intake vents on your tent as needed to get your air flow (and temps) where you want them AND still have negative pressure.

If for whatever reason....you can't use the room your tent is in as an actual lung room....OR....you can''t keep temps cool enough in the lung room...then IMHO you are going to need a bigger intake fan.

 

[neville hz]

OK....now I understand. You are correct....the way you are using the room the tent is in....it is not a lung room....it's just a room that the tent is in.

How big is the room the tent is in? Are you able to seal it off from the rest of the house (not necessary....but helpful)?
Generally people draw air into their tent from the Lung Room. You adjust the temp/humidity of the air into the lung room and then you use that air to cool your tent. If the temp of the air going into the tent is low enough.....then it's just a matter of opening enough vents into the tent to get the air flow necessary to keep temps where you want them. I think the 6" intake vent from outside is not providing enough air flow into the tent to keep your temps down.

Is it possible to have that intake send the nice cold air into your lung room and cool THAT room under 70f (20c)? If so then you can just open as many intake vents on your tent as needed to get your air flow (and temps) where you want them AND still have negative pressure.

If for whatever reason....you can't use the room your tent is in as an actual lung room....OR....you can''t keep temps cool enough in the lung room...then IMHO you are going to need a bigger intake fan.

The room the tent is in is roughly twice the size of the tent size.

I cant seal up the room but I'll try and turn it into as much of a lung room as possible..I'll get the inlet fan putting its air into the room instead of directly into the tent, open some vents and see what happens. If that doesnt work, I'll invest in a bigger inlet fan.

Just had a google on lung rooms ...thanks very much for the advice!!

 

[Bush Dr]

Thanks Dr Bush

Can you tell me the calculation I need to use to work out how to do that?

Your original answer times 2 or 3

 

[Old Toker]

..I'll invest in a bigger inlet fan...

If you do decide to up-size your intake fan...make sure everything will work together. For instance....one of the things we haven't discussed is how long your vents to the outside are....how many turns/bends....and what is the narrowest diameter through the entire length. Intake AND exhaust. There is a reason why the air flow in your tent is not sufficient to cool it even with 60f (15C) temps...and until you are sure where the problem is....hold onto your money.