heat issues

currently using a 6 inch duct fan for exhaust and a 4 inch duct fan for intake. i am exhausting outside of the room but still my tent temperatures reach upwards of 83 degrees. i have never had any luck growing cause of heat issues. wondering if its the duct fans not being strong enough or what. the leds on the glass my non contact temperature reader is reading 96 degrees. i thought heat travels up not down. i also got a fan blowing air upwards from the very bottom of the tent. please help.

Size of tent and cfms ?

3x2x6 4 inch is 100cfm and 6 inch 240cfm. i do have another 6 inch duct fan 240cfm that i was thinking about trying for an intake instead of the 4 inch

You don't need an intake. Only the exhaust matters. Completely eliminate the intake and see what happens. You can always put a second exhaust in if you need, but intakes don't help. 83 isn't bad either.

Kerovan said:

You don't need an intake. Only the exhaust matters. Completely eliminate the intake and see what happens. You can always put a second exhaust in if you need, but intakes don't help. 83 isn't bad either.

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Yes, if the tent has a hole for an intake, just leave it free and allow the exhaust fan to build pressure within the tent which will naturally pull in fresh air. What are your ambient temps like outside the tent?

OP, When you say duct fan, what do you mean? Like a real inline fan or a duct booster? Can you post a pic or a link to something the same as what you use.

Where is your thermometer placed?

You want your fans to blow across your plants. Heat will rise without facing fans up, but blowing across your plants will mix the air up, if its still (not moving) below the light it will warm up faster. Keeping it circulating will help.

What is the real wattage of the LEDs your using?

Corey has a point, duct booster fans are likely not really moving that much air if that is what you have. They are axial fans. There are I beleive, axial fans, squirell cage type and, centrifical. Axial is like the box fan in the living room, you get the most CFM per watt out this style by a long shot, however the weakness is they create little pressure, as in they move a lot of CFM but only if there is no resistance (Ducting and such). Squirell cage style is the least efficient CFM to watts but they create the most pressure, the air they move will have the ability to work its way through duct work and such, hence this is why your furnace has a squirell cage fan... Centrifcal or true inline fans are in the middle from my understanding.

I agree 83 isn't the end of the world, but for the finishing week or two would be nice to get that down, which I bet with some tweeks you can... If you have it, give the gals some silica if you are running higher heats, it helps their cells be tough to resist the heat.

Someone must have skipped the beginners guide to designing a grow setup.

Smaller intake than exhaust is a no-no.

Also important is the ambient temperature outside the tent...

Shugglet said:

Someone must have skipped the beginners guide to designing a grow setup.

Smaller intake than exhaust is a no-no.
...

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I'm curious as to why this is so. To me, it seems that is how you would want it from the standpoint of odor control if running a filter. it seems it would allow for negative pressure or close to for the air to have to exit out the filter and exhaust. whereas if you had a larger fan forcing air on the intake and the smaller exhaust couldn't keep up, it would push air out of anywhere that may have an air leak. Am i mistaken how I am interpreting that?

TCH said:

I'm curious as to why this is so. To me, it seems that is how you would want it from the standpoint of odor control if running a filter. it seems it would allow for negative pressure or close to for the air to have to exit out the filter and exhaust. whereas if you had a larger fan forcing air on the intake and the smaller exhaust couldn't keep up, it would push air out of anywhere that may have an air leak. Am i mistaken how I am interpreting that?

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The idea is you dont need an intake fan to begin with.

Shugglet said:

The idea is you dont need an intake fan to begin with.

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ok, but why should the intake not be smaller?

You vent fan should be able to suck the sides of your tent in. Duct fans won't move enough are expecialy when in flower.

TCH said:

ok, but why should the intake not be smaller?

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Puts added stress on the exhaust fan. Creates a bottleneck.

You will still get a negative pressure inside the tent with a larger passive intake than exhaust.

Shugglet said:

Puts added stress on the exhaust fan. Creates a bottleneck.

You will still get a negative pressure inside the tent with a larger passive intake than exhaust.

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thanks. that's what I was thinking but wasn't 100% sure. is there a simple equation to figure out what size intake is optimal?

No don't listen to him.
You don't need an intake but that guy isn't making sense.

With an intake you absolutely would want it smaller than exhaust, for odor controll as stated.
He's saying it is creating resistance on the exhaust fan, which it is, but as long as you are aiming to have negative pressure in your tent this will always be the case. Whether you run passive or forced intake.

I run an 8 inch fan and filter with a 4 inch for my intake. The intake is not sealed tight and there's also a vent hole, so it's forced intake with the ability for passive supplement.

I have a 4x4 tent with a 600w hps and my temps are about the same as yours with no heat stress.
But a few degrees lower would be beneficial.