When do 2 or more exhausts in the same room compete?

[tiffa]

In terms of competing with each other as opposed to adding to the extract, when do 2 extracts start interfering/pulling on each other?

How far apart do they need to be in the same room?
I've always needed to know this, now more than ever as Iam considering adding another in the attic.
Thanks for any advice

 

[Drop That Sound]

I would imagine they would equalize if they were the same exact model, and amount of ducting attached to each one.

You could simply damper the one that is winning down, to match the other.

There are some advantages, like cooling one side of a room more than the other, depending on placement.

Also If your intakes were insufficient or blocked somehow.. Let's say the room is completely sealed other than 2 exhaust ports and fans, they would be having a tug of war for sure.

I'm sure it always puts a little stress to have 2 running but usually no big deal.

Sounds like all you really need to do is make sure you have an even flow across the room so farther apart could work better, but totally depends on where your current exhaust an intakes are. If they are on the opposite sides of the room then you would want the 2 exhaust ports one one side and the intake/s on the other.

 

[Phaeton]

I switched to powered intakes instead of exhausts a few years back. Sucking the air out did not mix the cooling air with the room air very well, even with intakes and exhaust on opposite sides. The outlets suck from their immediate area and the room air moves too slowly to move the leaves.

Having a pair of intakes with the fans blowing into the room causes turbulence and a more thorough mixing of air inside the canopies. Leaves became more sturdy, less soft looking as moisture is carried out through the foliage.

The 9' x 7' growing area inside the 12' x 10' room uses a pair of 2300 CFM rated fans. The actual airflow is governed by the outlet damper, wide open puts the room at 6 degrees above ambient for summer. The intake fans are always full on so even with the damper shut way down for winter the air is still stirred.

 

[tiffa]

I switched to powered intakes instead of exhausts a few years back. Sucking the air out did not mix the cooling air with the room air very well, even with intakes and exhaust on opposite sides. The outlets suck from their immediate area and the room air moves too slowly to move the leaves.

Having a pair of intakes with the fans blowing into the room causes turbulence and a more thorough mixing of air inside the canopies. Leaves became more sturdy, less soft looking as moisture is carried out through the foliage.

The 9' x 7' growing area inside the 12' x 10' room uses a pair of 2300 CFM rated fans. The actual airflow is governed by the outlet damper, wide open puts the room at 6 degrees above ambient for summer. The intake fans are always full on so even with the damper shut way down for winter the air is still stirred.

Well explained, but my techy skills are limited, so how do you scrub the outgoing air? and wouldn't a normal oscillating pedestal fan have done the turbulence job? Cheers Phaeton

 

[Phaeton]

I live rural so the intakes are filtered to keep the bugs out and the outlets release all the smells to the world.

I am overly techy and have another five fans inside stirring the air as well, but they do not remove the layer of hot air that lies against the ceiling. Also those small air mover fans put out a tunnel of rapidly moving air that will abrade leaves if allowed to hit them directly.

But intake or exhaust problems are the same, if the fans are not matched then the stronger one tries to create a backflow on the weaker one. Matched fans set at the same speed are a must.
Matching fans with identical ducts and scrubbers should pull evenly.

I use a spray bottle of distilled water set on the finest mist setting and spray it everywhere with the fans running. This gives a very accurate picture of the airflow without making a mess or coating the leaves with smoke.

 

[tiffa]

I live rural so the intakes are filtered to keep the bugs out and the outlets release all the smells to the world.

I am overly techy and have another five fans inside stirring the air as well, but they do not remove the layer of hot air that lies against the ceiling. Also those small air mover fans put out a tunnel of rapidly moving air that will abrade leaves if allowed to hit them directly.

But intake or exhaust problems are the same, if the fans are not matched then the stronger one tries to create a backflow on the weaker one. Matched fans set at the same speed are a must.
Matching fans with identical ducts and scrubbers should pull evenly.

I use a spray bottle of distilled water set on the finest mist setting and spray it everywhere with the fans running. This gives a very accurate picture of the airflow without making a mess or coating the leaves with smoke.

The distilled water spray is genius ...you clever bastard...Can I live at yours?