Push or Pull through hood

jrainman said:

,The first thing that catches my eye is you not only have more bends (elbows) plus Over 90 deg bends ,So what does this do when you add 1 90 turn to air , well its equal to running 40 ft of straight duct (lots of resistance) , so the way you are ducted in now is much better see how you are going straight with no bends, but those reducers are still hurting your fan, So why did a problem arise in your old setup it was not weather you pushed or pulled add 90s caused this, believe it or not but thats what happened

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Don't mean to hijack the thread, but your comments forced me to post a couple questions that have been rolling around my noggin...

My grow room is currently in my basement. In flower, I am drawing air through 6" ducting (4' rigid + 3' flexible on either end of the hood) using a 440CFM fan at about 60% power. Currently, intake and exhaust are both the ambient basement air (which is working out fine in the winter months). The temp of the basement is ~65* and 12 hours of running the HID light and fan raises the basement temp less than 1*. I am concerned that in the summer months with higher starting temps that I will hit a tipping point where temps will rise dramatically.

Is this a valid concern and should I look to closing the hood cooling circuit by drawing and exhausting air outdoors? If I wanted to draw/exhaust from/to the outdoors I would have to add 2 - 90* elbows + ~16' of rigid ducting - is that feasible with the single fan? What if I added an intake fan to the loop?

No def doable ,its ok to use the 2 elbows , but if you can 45 deg them stright to 45 deg = less resistance , but also up the diameter of the duct on the fresh air side , I would also think about putting a T in the line ,and put a damper on bull of the this way you can use the damper to mix fresh air with your basement air to better regulate the temps and humiditiy

I've always been against having an intake and an exhaust fan on the same duct. To me it seems like overkill. It seems like you are better off increasing duct diameter or just getting a larger fan at the expense of efficiency and noise. Many on here recommend running both intake and exhaust fans.

The biggest reason I do not like intake fans in this business is that you run the risk of pressurizing your room. Forcing unfiltered air out to the public. To me filtered exhaust fans are where it is at.

What are your thoughts on this jrainman?

agree really no need for intake fan(makeup) fan if properly ducted and fan size cfm correct for cubic ft of room size

Mrshim2 as per you requet to my set up ,pictures my fan is in a attic crawl space , diy carbon filter and damper to regulate cfm also in attic crawl space

joe macclennan said:

I've always been against having an intake and an exhaust fan on the same duct. To me it seems like overkill. It seems like you are better off increasing duct diameter or just getting a larger fan at the expense of efficiency and noise. Many on here recommend running both intake and exhaust fans.

The biggest reason I do not like intake fans in this business is that you run the risk of pressurizing your room. Forcing unfiltered air out to the public. To me filtered exhaust fans are where it is at.

What are your thoughts on this jrainman?

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Appreciate the responses.

To clarify, this is only for hood cooling only. I have a separate loop for air exchange for the rooms: (flower room) 10" x 24" filter >> 6" duct >> (veg room) 6" x 4" x 6" T (10"x 6" filter off of the 4" T) >> 440CFM fan (pull) to basement. Both rooms have passive air intake under the floors.

For some reason i cannot get to the 13th page, 12 is the max.

Jrainman, could i ask you man, i want to pull some air dude, now i live in a country where the variety of inline fans arent too big & the pretty expensive.

I found a few fans, the fans that couldnt reach 300 Pa until airflow was completely obstructed i scraped. Reason being am i going to use ducting.

I have My 600watt in my Super sun 2 in a 3x3x6 & i might go use a carbon filter.

Fans : All 6" & based on max Pa

HIT Series Inline : 275 cfm at 0 Pa , 0 Cfm at 350 Pa ( 90 $ Fan : 70 $ Speed controller ) Confirmed the speed controller has 8 settings

Xpelair XID 150 : 360 CFM at 0 Pa , 0 Cfm at 300 Pa ( 150 $ Fan : 100 $ Speed controller ) Confirmed the speed controller has 8 settings

Ox tube fan 150 : 315 Cfm at 0 Pa , 0 Cfm at 348 Pa ( Price : 100 $ Fan : 40 $ Speed controller) still awaiting speed controller info though might only be 3 speed.

From the specifications ive explained plz correct me if im wrong, i know the fans still operate at like 0.0075 cfm at their max Pa although it is necessary to describe these figures ?
Or is MAX Pa and cfm all that matter ?

For me the ox tube fan looks like the best best although i have phoned the sales person twice to send me a another spec sheet for the fan and speed controller, I also tried to find out if this is the company he gets it from.
Link : http://www.ox-fan.com/Uploads/Products/decc1ae71c797cec_WY7XR.pdf Local : Spec sheet & Speed controller info : View attachment 2568394View attachment 2568398^

HIT 150 : http://www.hydor.com.au/images/pdf/HIT.pdf Speed Controller for HIT ( REB2.5N Controller ) : http://www.solerandpalau.co.uk/docs/catalogo_general/en_665_674_acces_electrics_fid3257.pdf

XID 150 : http://www.dealec.co.uk/acatalog/pdf/xpelair/xpxid.pdf Speed Controller : http://www.qssupplies.co.uk/bathroom-furniture-shower-taps/67065.htm

Last question, could you also please explain what you meant when you said 6" is meant for 150cfm max ?

Hope i didnt type too much but any help will be appreciated ! Much thanx !

peace !

gonna need more info, is this just for exhausting your room ,or lighting also, your choice in fan is fine way more CFM then really needed 3ft x 3ft = 9 sq ft + 6 ft high room = 56 cubic Ft . ,need to know where you are dumping the exhaust air also , and you need to supply enough air to the room for the fan to properly get the 315 cfm rating. the other thing NO SPEED Controller they cut the life of the fans motor winding down and also will contribute to bearing falure , that why if you read the specs it says Operation CONTINUES RUN ,also if the fan was designed to handle a speed controller the option would be made avalible by the fan company, I would set this fan up with a T and a damper to control the CFM , and if you are incorperating the lighting you will definitly have to slow the air down ( CFM) you see there is a point that you are diminishing heat transfer where if you are moving air across a object that you want to remove BTUs from . you have to understand how british thermal units work (BTU) and how to calculate how much air needs to move across a certain amount of sq inches to effectivly remove heat , So this ties in to your last question about 6'' round can only support at best 150 cfm , because only a certain amount of sq inches of are can phisicaly pass through ,it like the old saying you cant put 10 pounds of shit in a 5 pound bag.

I think being you have only a 1 deg diff from your room temp your lighting will remain having this 1 deg diff ,but as room temp goes up so will the light temp but should hold that 1 deg , you have the idea though using the 3 n 4 inch ducting to your lighting, witch only about 40 cfm that you are moving across the light ,you are a good case in showing people that they think more is better. i would up the intake size of your passive air to about 100 sq inches for that 440 cfm fan though 10'' x 10'' opening or 10'' round will do ,you will increase your air exchange and most likly get a better humidity level.

yankeegreen said:

Appreciate the responses.

To clarify, this is only for hood cooling only. I have a separate loop for air exchange for the rooms: (flower room) 10" x 24" filter >> 6" duct >> (veg room) 6" x 4" x 6" T (10"x 6" filter off of the 4" T) >> 440CFM fan (pull) to basement. Both rooms have passive air intake under the floors.

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jrainman said:

I think being you have only a 1 deg diff from your room temp your lighting will remain having this 1 deg diff ,but as room temp goes up so will the light temp but should hold that 1 deg , you have the idea though using the 3 n 4 inch ducting to your lighting, witch only about 40 cfm that you are moving across the light ,you are a good case in showing people that they think more is better. i would up the intake size of your passive air to about 100 sq inches for that 440 cfm fan though 10'' x 10'' opening or 10'' round will do ,you will increase your air exchange and most likly get a better humidity level.

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Thanks again for taking the time to share your knowledge and experience!

No prob any time , I did follow your build and remember that I thought your air movement concept was good ,by picking up the cool air from the basement floor ,but would drop in more registers in the floor.Now if I can just learn how to grow better id be a happy camper here .

Edgar9 said:

I've always pulled through an air cooled hood b/c that seem to be the logical thing to do. Recently a guy at a hydro store said I should be pushing through the hood with an inline fan b/c it saves the fan's motor since you're not exposing it to hot/warm air. Another guy at a different hydro store said alway pull through the hood for best results.

Personally I think pulling is better and the fan's are designed to handle the heat.

Any opinions?

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i don't think there is much choice if you only want to use 1 fan, fan>lights>filter is the standard way to do it, although some folk do place the filter on the outlet side of the fan to save space in tents filter>fan>lights

if you only use one fan you will have to suck air through the lights as this fan will also be responsible for creating an air flow around the plants
if you want to remove the air from a given space it is more efficient to suck it out, as this instantly lowers the pressure and brings new air in
the alternative is to blow new air in to raise the pressure to force old air out, this is nowhere near as efficient
so when you only use one fan, you only really have one choice and that is to use it to extract air out , creating a negative pressure

if you are prepared to use 2 fans, then you can use one fan to blow cold air through the lights, this works much better separating the task of cooling the lights and refreshing the air space with a fan for each job

when you suck air through the lights with the 1 fan setup you suck the air from high up as you are also using this fan to extract/remove the hot/used co2 depleted air in the grow space, this warm air sucked through the lights does not help to cool the lights as much as blowing very cold air through them from outside , or pushing even cooler air through the lights from a small portable air conditioner also the positive pressure created in the hoods will stop the air in the grow space (negative pressure entering the hood ducting so no filter is needed on the lights

you are then free to use your 2nd fan with carbon filter to extract the air space itself, the 2nd fan does not need to be near the lights and can be placed in the best position high up in the grow space at right angles to the inlet so it extracts all the air in the space efficiently from one end to the other pulling all the air across the space as it is extracted

peace

jrainman said:

gonna need more info, is this just for exhausting your room ,or lighting also, your choice in fan is fine way more CFM then really needed 3ft x 3ft = 9 sq ft + 6 ft high room = 56 cubic Ft . ,need to know where you are dumping the exhaust air also , and you need to supply enough air to the room for the fan to properly get the 315 cfm rating. the other thing NO SPEED Controller they cut the life of the fans motor winding down and also will contribute to bearing falure , that why if you read the specs it says Operation CONTINUES RUN ,also if the fan was designed to handle a speed controller the option would be made avalible by the fan company, I would set this fan up with a T and a damper to control the CFM , and if you are incorperating the lighting you will definitly have to slow the air down ( CFM) you see there is a point that you are diminishing heat transfer where if you are moving air across a object that you want to remove BTUs from . you have to understand how british thermal units work (BTU) and how to calculate how much air needs to move across a certain amount of sq inches to effectivly remove heat , So this ties in to your last question about 6'' round can only support at best 150 cfm , because only a certain amount of sq inches of are can phisicaly pass through ,it like the old saying you cant put 10 pounds of shit in a 5 pound bag.

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Thank you for your response jrainman, appreciate you giving a hand here man.

I am exhausting the lighting & the cab at the same time out of a window.

I was originally going to go with a two stage vent setup, 2 inline fans one for the hood & one for the cab. Although i got suggestions that using one fan would be fine. Do you say it would be better to ventilate with separate fans or is a single fan fine ?

My exhaust will be dumped out the window, my setup will roughly look like this

I definately see what you mean by needing to supply the room with enough air for the fan itself to reach its optimal air flow, if its too constricted it wears out the fan, i noticed from mr2shim & read your comments there.
Do you mean if the fan wasnt designed for a speed controller & you add one you it diminishes bearing life drastically ?
The fan companies do have these controllers available for the fans although they all differ, the HIT series has two controllers available a 2 speed switch & a 8 speed switch, The XID 150 has
only one speed controller which has 5 speeds & the ox fan has a speed controller with 3 settings.

Would you suggest using a T with one fan or separately venting the light & cab with two ? From what ive seen if im not mistaken you can wire these fans on the low setting & the high setting
without using a controller & if i dont need a controller i could pretty easily afford two of them.

I understand where you coming from with BTU's and effectively removing the heat, you cant try and pull more air than what there is to pull & effectively moving the heat you need to have a certain cfm and not overkill, if you do have overkill extraction will it cause the something like the venturi effect ?

You cant put 10 pounds in a 5 poind bag, perfect way of explaining : )

Dude thank you so much for the help, i appreciate it & please do not hesitate to message me, even if i dont know much i will research and try help as best as i can.

Peace out ! eace: