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Offlineadnankaysar
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Registered: 04/03/14
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exhaust fans for grow room
    #21678258 - 05/14/15 09:34 AM (8 years, 8 months ago)

Dear all,

My grow room size is 540 square feet.

Precisely w*l*h is 20*27*13 feet in size which is rectangular in shape.

For FAE how many fan i need to install if it is 12" fan.

Also where i would install on top or bottom side.

Thanks


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OfflineGr0wer
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Re: exhaust fans for grow room [Re: adnankaysar]
    #21682064 - 05/15/15 08:03 AM (8 years, 8 months ago)

Get your cubic feet and find out what the cfm is of your fans. Decide what rate of air exchange you want and that will let you know how many fans to use. I would recommend using fans blowing in for positive pressure, most fans are not rated to move %100 humidity and may fail over time. Positive pressure also gives you the opportunity to filter all incoming air for a cleaner environment. Just remember filtering is a restriction and will reduce airflow volume.


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OfflineGr0wer
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Re: exhaust fans for grow room [Re: Gr0wer]
    #21682079 - 05/15/15 08:09 AM (8 years, 8 months ago)



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Invisiblelipa

Registered: 07/24/07
Posts: 2,684
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Re: exhaust fans for grow room [Re: adnankaysar] * 1
    #21682433 - 05/15/15 10:14 AM (8 years, 8 months ago)

Your grow space is 7020 cubic feet. To get 10 exchanges an hr. Multiply 7020 x 10 then divide by 60.

For a 12 inch duct you will need to be able to adjust the speed of the fan from a maximum CFM of 1170 minus 25% because as you increase the blocks in the room the volume decreases and will increase the exchange rate and speed of the air which will cause your sensors to not read correctly. 

For this above to work the duct must stay 12 inches. It is important that the air moves at a rate of 2ms through the room for wet dry bulb readings  to be accurate.

A 12 inch duct providing an air speed of 2ms will require a fan pushing the air through it at 1236 CFM.  You can calculate it here. Since it is a little high for the amount you want to exchange the air you will need to cycle it down. You will want to distribute the air evenly through the grow room by the use of an evenly perforated sock.

It should enter the room as high as possible. Especially if the humidity is being carried through with the air.


Edited by lipa (05/15/15 10:20 AM)


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OfflinepoofterFroth
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Re: exhaust fans for grow room [Re: lipa]
    #21682927 - 05/15/15 12:37 PM (8 years, 8 months ago)

Quote:

lipa said:
Your grow space is 7020 cubic feet. To get 10 exchanges an hr. Multiply 7020 x 10 then divide by 60.

For a 12 inch duct you will need to be able to adjust the speed of the fan from a maximum CFM of 1170 minus 25% because as you increase the blocks in the room the volume decreases and will increase the exchange rate and speed of the air which will cause your sensors to not read correctly. 

For this above to work the duct must stay 12 inches. It is important that the air moves at a rate of 2ms through the room for wet dry bulb readings  to be accurate.

A 12 inch duct providing an air speed of 2ms will require a fan pushing the air through it at 1236 CFM.  You can calculate it here. Since it is a little high for the amount you want to exchange the air you will need to cycle it down. You will want to distribute the air evenly through the grow room by the use of an evenly perforated sock.

It should enter the room as high as possible. Especially if the humidity is being carried through with the air.




This is great info, but I'm a little confused now. I'm also working on redesigning my ventilation system/design.

What is "ms" and will movement over 2ms, cause an inaccurate reading? Does this number only matter for a wet/dry bulb measurement?
How are recommended grow room evaporation rates calculated/considered when choosing ventilation fans, or is this something more for an in-room air circulation fan to effect?

Also wondering if your explanation is referring to intake fans, exhaust fans, both - or does it not matter?

I think its also important to consider the CFM drop caused by filters, increasing spore loads, and ducting angles when choosing your fan/s. So having a bigger fan, that can be cycled down if needed would be primo.

I was recommended by some heads at the growshop recently to exhaust from the bottom of my room if trying to move out Co2. They claimed Co2 is heavier and sinks...although I swear I've read multiple places that it stays mixed with the room air...:shrug: I guess proper air circulation should help keep it all mixed so it probably doesn't matter.

Right now my exhaust is on the ceiling, to help pull out the hotter air during the summer months. Once again, proper air circulation should fix this temperature differential, right?

I use an inline dryer exhaust boosting fan that's rated for high moisture usage. So far its holding up, and I can spray it out with a hose no problem when it needs to be cleaned.


--------------------


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Invisiblelipa

Registered: 07/24/07
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Re: exhaust fans for grow room [Re: poofterFroth]
    #21683115 - 05/15/15 01:23 PM (8 years, 8 months ago)

Quote:

poofterFroth said:

This is great info, but I'm a little confused now. I'm also working on redesigning my ventilation system/design.

What is "ms" and will movement over 2ms, cause an inaccurate reading? Does this number only matter for a wet/dry bulb measurement?
How are recommended grow room evaporation rates calculated/considered when choosing ventilation fans, or is this something more for an in-room air circulation fan to effect?

Also wondering if your explanation is referring to intake fans, exhaust fans, both - or does it not matter?

I think its also important to consider the CFM drop caused by filters, increasing spore loads, and ducting angles when choosing your fan/s. So having a bigger fan, that can be cycled down if needed would be primo.

I was recommended by some heads at the growshop recently to exhaust from the bottom of my room if trying to move out Co2. They claimed Co2 is heavier and sinks...although I swear I've read multiple places that it stays mixed with the room air...:shrug: I guess proper air circulation should help keep it all mixed so it probably doesn't matter.

Right now my exhaust is on the ceiling, to help pull out the hotter air during the summer months. Once again, proper air circulation should fix this temperature differential, right?

I use an inline dryer exhaust boosting fan that's rated for high moisture usage. So far its holding up, and I can spray it out with a hose no problem when it needs to be cleaned.




Meters per second.

A lot of the sensors that take wet/dry/bulb readings are made to work in an environment that has an air speed of 2ms. I do not know why they do.

I was referring to feeding continuous air into a grow room by any means.  Exhaust fans are not needed unless your in a huge warehouse with a lot of volume. Usually exhaust dampers are used.

CFM drop is why you should have some form of speed control and a hand held measuring device to fine tun the system withing the growing room. You can also just do it by feel as you start growing.

You could put the exit anywhere you want.  On top it will help get some heat out but honestly it hasn't cause any problems with heat for us having the exit on the bottom. We have circulating fans in the grow room moving things around.


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OfflinepoofterFroth
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Re: exhaust fans for grow room [Re: lipa]
    #21683410 - 05/15/15 02:44 PM (8 years, 8 months ago)

Quote:

lipa said:
Quote:

poofterFroth said:

This is great info, but I'm a little confused now. I'm also working on redesigning my ventilation system/design.

What is "ms" and will movement over 2ms, cause an inaccurate reading? Does this number only matter for a wet/dry bulb measurement?
How are recommended grow room evaporation rates calculated/considered when choosing ventilation fans, or is this something more for an in-room air circulation fan to effect?

Also wondering if your explanation is referring to intake fans, exhaust fans, both - or does it not matter?

I think its also important to consider the CFM drop caused by filters, increasing spore loads, and ducting angles when choosing your fan/s. So having a bigger fan, that can be cycled down if needed would be primo.

I was recommended by some heads at the growshop recently to exhaust from the bottom of my room if trying to move out Co2. They claimed Co2 is heavier and sinks...although I swear I've read multiple places that it stays mixed with the room air...:shrug: I guess proper air circulation should help keep it all mixed so it probably doesn't matter.

Right now my exhaust is on the ceiling, to help pull out the hotter air during the summer months. Once again, proper air circulation should fix this temperature differential, right?

I use an inline dryer exhaust boosting fan that's rated for high moisture usage. So far its holding up, and I can spray it out with a hose no problem when it needs to be cleaned.





I was referring to feeding continuous air into a grow room by any means.  Exhaust fans are not needed unless your in a huge warehouse with a lot of volume. Usually exhaust dampers are used.




See, this is kinda what confuses me.
Many farmers(not mushroom farmers) with greenhouses I've talked to say, "no, no. you pull the air - not push it and the poly tube is recirculated air"

The point being to pull out the hot air for cooling. Often a large-wall-sized evaporative cooler system is used, pulling fresh air through with an exhaust fan..

Are mush houses just built the opposite because of extreme humidity passing thru expensive fans.


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Invisiblelipa

Registered: 07/24/07
Posts: 2,684
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Re: exhaust fans for grow room [Re: poofterFroth]
    #21683551 - 05/15/15 03:17 PM (8 years, 8 months ago)

Here is 2 examples.

The first one is what we use currently for oysters, but we have an exhaust port near the bottom end of the room.

The second is the most common when you add cooling and heating. When the Co2 sensor calls for fresh air the damper on the recirculating duct closes and the fresh air damper opens until it calls off.  Regardless of whether it is re-circulating air or not it can still manage the temperature and humidity. As you can see in the drawing they have a fan on exit. It is not necessary like I said before and you can simply place a damper here with a sock over it to keep insects from entering.

The problem with the second is the spores.  One reason why we use the first system. If you grow oyster I would just do away with the re-circulation. It is not worth it. You would have to put an electrostatic filter on the re-circulating duct to prevent the heating and cooling elements from getting clogged all the time. 


Edited by lipa (05/15/15 03:23 PM)


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OfflinepoofterFroth
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Re: exhaust fans for grow room [Re: lipa]
    #21687279 - 05/16/15 02:31 PM (8 years, 8 months ago)

Quote:

lipa said:
Here is 2 examples.

The first one is what we use currently for oysters, but we have an exhaust port near the bottom end of the room.

The second is the most common when you add cooling and heating. When the Co2 sensor calls for fresh air the damper on the recirculating duct closes and the fresh air damper opens until it calls off.  Regardless of whether it is re-circulating air or not it can still manage the temperature and humidity. As you can see in the drawing they have a fan on exit. It is not necessary like I said before and you can simply place a damper here with a sock over it to keep insects from entering.

The problem with the second is the spores.  One reason why we use the first system. If you grow oyster I would just do away with the re-circulation. It is not worth it. You would have to put an electrostatic filter on the re-circulating duct to prevent the heating and cooling elements from getting clogged all the time. 




Hey cool link... but why is there no exhaust exit in the first diagram? Where does the spent air go?

Are you using a fan on your exhaust port and how is it sized in comparison to your fresh air intake? I thought I read something about the diameter of your exhaust should be no larger than half the size of your intake. Maybe this only applies to using a one intake fan/positive pressure system?


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Offlineadnankaysar
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Registered: 04/03/14
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Re: exhaust fans for grow room [Re: poofterFroth]
    #21704824 - 05/20/15 11:59 PM (8 years, 8 months ago)

Thank you guys, invaluable info i have got,
need to think abut how i can implement your advices in my grow room


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Offlinebeastcoast
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Registered: 03/29/15
Posts: 92
Last seen: 4 years, 7 months
Re: exhaust fans for grow room [Re: adnankaysar]
    #21704939 - 05/21/15 12:38 AM (8 years, 8 months ago)

570 sq ft?? that's a lot of mushrooms


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