Where to best place your extractor fan???

Ok im using a few stand alone cupboards for my grow - one veg and one flowering... i have a large hole at the bottom and top of each for air to get in and out. The bottom hole is passive and the top hole has ducting from a carbon filter coming out of it - which goes to the floor where my fan sits on the carpet blowing warm air to somewhere safe.

My question is... should i be mounting the fan inside the top of the cupboard rather than outside it and down on the floor to get better ventilation - im guessing im maybe losing a lot of power from the fan as it has to draw air right the way up the ducting and into the filter where it could be mounted closer to give better extraction?

What do you think?

whitewidow2 said:

Ok im using a few stand alone cupboards for my grow - one veg and one flowering... i have a large hole at the bottom and top of each for air to get in and out. The bottom hole is passive and the top hole has ducting from a carbon filter coming out of it - which goes to the floor where my fan sits on the carpet blowing warm air to somewhere safe.

My question is... should i be mounting the fan inside the top of the cupboard rather than outside it and down on the floor to get better ventilation - im guessing im maybe losing a lot of power from the fan as it has to draw air right the way up the ducting and into the filter where it could be mounted closer to give better extraction?

What do you think?

Click to expand...

Pictures and dimensions of the cupboards would be great!

GrizzlyAdams said:

Pictures and dimensions of the cupboards would be great!

Click to expand...

heres a pic of the cupboard sorry its quite dark but my ladies are sleeping in there...

i took dimensions its 1.67 x 2.66 x 5.77ft = 25.6 cubic feet area

if i remember correctly air should be changed 3 times per minute so basically my fan should ideally have a cfm rating of 75 or above - ill need to check it. Inside i have a single 150w large red spectrum envirolite doing the flowering and it does get quite hot in there... Obviously the carbon filter adds resistance to the fan - i just dont feel as though its pulling much air through from inside the cupboard - can anyone confirm if i should set it up differently thanks.

Ok im further confused by the fact that the box gives me cfm ratings of 145m3 per hr on slow speed and 187m3 per hr on fast...

Does this mean its only gonna pull 2.41m3 per min and 3.11m3 per min respectively?

Am i right in thinking the air need to be changed 2 or 3 times per minute or have i gone wrong somewhere???

Need help.

Can anyone help me on this and the correct air exchange rates?...

thanks.

bump help..

found this... hope it helps people.....


Q: What size extractor fans do I need?

Below are two ways you can work out the size of extractor fans you will need in your grow room.

1. This method is based on the volume of the grow area and is perfectly suitable for small to mid sized grow rooms.

First calculate the size of the room in cubic meters (m3): Length x Width x Height in meters = size of room in cubic meters.

Then multiply the total m3 by 25 to give you the air exchange needed in one hour.

Add 30% to this figure to allow for the inefficiency created by using carbon filters and lengths of ducting and the figure you will have is the air exchange rate needed in m3/hour for your grow area.

Because all extractors are sold with a m3/hour air exchange rate, it is a simple matter to select the correct size fan(s) you will need. For example, if you have calculated the air exchange rate needed is 450m3/hour then this could be achieved by using one exhaust fan rated to 450m3/hour or by using two fans, one for input and one for exhaust that together total this amount. If you use two fans (recommended) make sure that the exhaust fan is approximately 50% larger than the input fan.

2. This formula is used by commercial growers and is based on the number of lights used. This is recommended for large grow rooms and guarantees the control of temperature regardless of the number of lights being used.


Extraction:

Take into account at least 200m3 of exhaust for each 400w lamp
Take into account at least 300m3 of exhaust for each 600w lamp

Add approximately 30% more exhaust to this to allow for the inefficiency created by carbon filters and lengths of ducting.

Intake:

Intake should be approximately half the volume of the exhaust.

Example: A grow room with 5 x 600w lamps would be 5 x 300m3 = 1500m3 of exhaust. Add around 30% to this (approx 500m3), and you will need 2000m3 of extraction. The size of the intake fan should be approximately half of this, so about 1000m3.

oops i had converted to feet to start with and then used that method but its on meters all the way thru... so basically my grow area needs to extract air at a rate of 22.75m3 per hour given the inefficiencies caused by the carbon filter and ducting, my vents tt fan has a m3 per hour rate of 145 so im guessing thats plenty... ive made some adjustments too with the fan positioning it at the top of the growroom so hopefully this setup should work fine for a while - just need to get a hygrometer inside to see how the temps and humidity is as i have no idea at the moment.

heres some pics

helpful guide there mate, guna check my space to fan ratio see how it works out, my plants are fine but curious
thanks

Cool just keep everything in meters and you will be fine... i converted to feet as folk are always talking about a 4x4 room or 6x6 room on here.

The side of the box for the fan i have gave me its cfm rating in m3/h.

All in the science.