Tutorial Ventilation 101

[Some1uKnoOf]

The reason why I opted for the 6" was based off the CFM/temp chart. I am aiming to keep my box temps at 75-78ish and based off that chart I would need 250CFM and 150CFM respectivly. The little extra was to compensate for static pressure from the insulated ducting curves. The reflector is air cooled with a 6" flange, cord out the top of the reflector. I didn't even think about the heat from the lamp damaging my fan, good lookin out

I agree with your math regarding the CFM values, but you don't actually use two fans at the same time to get that effect, it is either one or the other. Venting the light directly will remove some proportion of the heat and reduce the heat load on the main cab area. As I said, I just don't know how to figure out how much. You should almost surely be in the good zone if you vent both areas with that much fan power. It's good to have headroom but I think a 150 and 320 in your situation may cool more than you would expect.

So thats the general plan, headed to Lowes this weekend for lumber and will start on the frame early next week...cant wait to get my 400W up'n runnin. When I get to the stage for temp testing I will be in touch. By chance to you know which is quieter, the S&P series or the Panasonic WhisperLine? The sone rating for the 6" whisper line is 1.4 which isn't bad but I can't find any stats for the S&P's.

I have no idea what fan is quieter.

Did you get the box started yet?

Be cautious when you spark up the light the first time. If you haven't played with them before, they can be extremely bright in a closed room. It's kind of like the first time you hear a gun shot indoors, only visual. It will put out a whole bunch of light and if you are worried about the neighbors, you must do it in a room with solid walls and not count on curtains. You might want to ignite it during the daylight hours to make any leakage less noticeable. For instance, if you are in an attic and turn it on, you will most likely get leakage through the eave vents if they are around. Just be careful to think of things like that because it can make the neighbors notice. Always do a perimeter scan by walking around with the light on indoors so you have an idea what kind of photon leakage you have. My cab is safe when the door is closed but it can be noticed when I open up to peek.

- SomeoneYouKnow

 

[staceyadams]

Hey all, I have a question about my fan for you, as I am HORRIBLE at the technology side of things.

I just set up my first tent grow (64"x20"x36"), and I'm using a 400w light with a 4" inline fan and filter for exhaust. I'm going to be running the lights 12/12 from seed and was curious as to how often I should have my fan going. Do I leave it on 24/7? Thanks for any help you can give me!

 

[kiheibuilt]

Redgreenry, thanks for the time, effort and the following-up that you've done with this thread. It's been extremely helpful for me as I'm in the planning process. I'm on the verge of starting a small cab grow, proper air exchange and stealth is top priority for me to try and figure out since this is where I lack the knowledge. Thank you!

 

[guest 77721]

Hey there stacey,

you will want to run your fan 24/7 for ventilation for the plants and to contain the fragrance as the plants mature.

Hey kiheibuilt - thanks for popping in. I'm happy to help out!

 

[staceyadams]

Thanks Redgreenry! I appreciate the help!

 

[SmokinSHO]

-

 

[guest 77721]

Hmmmm..... that's a lot of info. From what I can tell, your cab intake should be sized to 56 sqin and you have 156 so the intakes aren't the problem. The 6" duct has an area of 30 sqin so your intakes are already 5x oversize.

Your cab needs 126 CFM to cool within 10*F and it's not happening using a 440 CFM fan with a scrubber plugging up the airflow.

There are 4 solutions.

A) reduce lighting
B) upsize the scrubber area to pass > 126 CFM with your existing fan.
C) replace the fan with a higher static pressure model to overcome the restriction of the scrubber
D) separate the cooling and ventilating functions using two smaller fans and a smaller scrubber.

My response to these type of questions will always be D.

The one pass fan+scrubber is a brute force design that uses oversized equipment with poor results.

*******************************************************************************************
Now you can separate your lights and scrubber into two circuits with a Y. The tendency will be for the air to flow through the path of least resistance which will be the light hood. You will likely have to block the intake to the lights to balance the airflow through the scrubber. This is a more workable solution and you can probably downsize the fan along the way as well.

Fan/-----[Lights]-------< Room Air
.... \-----[Scrubber]----<Growbox>--<Room Air

 

[SmokinSHO]

-

 

[guest 77721]

Oh I see...

I'd get some cardboard or some plastic containers from the kitchen and make a sleeve to slip over that pipe. You could experiment to see if there is an improvement. It doesn't have to be made from anything special.

 

[Amstel Light]

bump

 

[rasputin]

Quick question... 5x5 room, 1K HPS temps are 90 rH 45% with no fan, I've done a few tests. Wondering what some thoughts are on running a 6" inline connected to hood, blowing out the room thru ducting pulling air thru the hood and a carbon filter. I keep coming across conflicting information regarding the sequencing of fan, hood and filter.

I'm thinking -- outside room < Fan / Light / Filter.

Good? Bad? Doing some preliminary brainstorming to see if this particular setup needs any tweaking before I need it to be running correctly. Appreciate any input or feedback.

 

[guest 77721]

Generally you want to do outside exhaust <- Fan -<Light -<Filter. This keeps negative pressure inside the ducting so the smelly air doesn't leak out, however any leaks in will still pick up some smell.

My issues with this design is the sizing of the fans and scubber. You will need around 300 CFM to remove 1000 W of heat from the room. By using a vented hood and remote ballasts and letting the exhaust temperature run 30* above ambient, you can get away with running a 110 CFM through the hood.

The tricky part is to get the right airflow by matching a scrubber and oversizing the fan.

 

[Sirus]

Couple of questions for you Red. I have read tons of posts and tbh alot of

people sound credible but its easy to get lost in the info. I have read this

thread and since you are the resident expert I would like your take. I will

be running a 2x4x6 custom cab "armorie", stealth is of paramount

concern. I have a 400W a/c Xtrasun reflector I recieved as a project

starter. I have decided to go with S&P inlines as they seem to be the

quietest. I am looking at this fan with a speed controller
S&P Soler & Palau Ventilation Fans : TD-200x Inline Mixed Flow Duct Ventilation Fan Turbo - H 478 CFM L 419 CFM - 8" Duct

and this as a filter...

CAN FILTER 66 Max CFM: 412 cfm (non-recirculating) Min CFM: 206 cfmDimensions:
(with pre-filter)·Outside Diameter: 305mm/12"
·Height: 660mm/26"
·Total Weight: 20kg/44lbs.
·Carbon Weight: 14kg/31lbs.
·Carbon Bed Depth: 50mm/2"Max Operating Temp: 176º F / 80ºC Pressure drop
at max CFM:180pa/ .75wg Flange:*6", 8" or 10"

Ambient temps are 70F controlled and the plan was to set up as

filter>lamp>fan>exhaust. I had orginally choose a much less powerful

combo S&P TD 150 with 9000 can filter but after some IC reader input I

"scrubbed" this idea. Appericate your take as well as anyone else who

would like to comment.

 

[qbert]

Generally you want to do outside exhaust <- Fan -<Light -<Filter. This keeps negative pressure inside the ducting so the smelly air doesn't leak out, however any leaks in will still pick up some smell.

Hmm, I personally think Outside Exhaust <- Light <- Fan <- Filter is a better idea.


As you said, any leaks before the fan can suck smelly air into the exhausting stream, so keeping the length of duct under negative pressure to a minimum is good. If there's a leak under positive pressure - i.e., after the fan - it will simply push already scrubbed air through the leak, and clean smelling air can go anywhere for all we care. Also, keeping the fan before the light keeps the hot air out of it. And, of course, those hoods are tough to seal so I'd rather have clean air push out of leaks in it, which won't affect me, rather than fight all the leaks cause smelly air keeps getting sucked into the post-scrubbed exhaust stream.

Don't ya think?

 

[guest 77721]

Personally, I don't think using a furnace fan to force a high volume of cooling air through a scrubber is particularly stealthy.

Take a typical 400 W light with a 400 CFM Vortex and a CanFan combo that passes less than 200 CFM with a noise level of 60-70 db.

The box only needs about 20 CFM to ventilate the plants.

This design uses a 200% oversize fan to pass 90% cooling air through the scrubber.

Take the same light and growbox and split it into two ventilation circuits.
Get a 150 CFM AXIAL fan and run it unrestricted through the lights with a noise level of 30-35 db.

Get a small blower and fan combo sized to give one air change every 1-5 minutes and you're all set.

The noise level will be less than 40 db which is at least 20x quieter than using a furnace fan.

Couple of questions for you Red. I have read tons of posts and tbh alot of

people sound credible but its easy to get lost in the info. I have read this

thread and since you are the resident expert I would like your take. I will

be running a 2x4x6 custom cab "armorie", stealth is of paramount

concern. I have a 400W a/c Xtrasun reflector I recieved as a project

starter. I have decided to go with S&P inlines as they seem to be the

quietest. I am looking at this fan with a speed controller
S&P Soler & Palau Ventilation Fans : TD-200x Inline Mixed Flow Duct Ventilation Fan Turbo - H 478 CFM L 419 CFM - 8" Duct

and this as a filter...

CAN FILTER 66 Max CFM: 412 cfm (non-recirculating) Min CFM: 206 cfmDimensions:
(with pre-filter)·Outside Diameter: 305mm/12"
·Height: 660mm/26"
·Total Weight: 20kg/44lbs.
·Carbon Weight: 14kg/31lbs.
·Carbon Bed Depth: 50mm/2"Max Operating Temp: 176º F / 80ºC Pressure drop
at max CFM:180pa/ .75wg Flange:*6", 8" or 10"

Ambient temps are 70F controlled and the plan was to set up as

filter>lamp>fan>exhaust. I had orginally choose a much less powerful

combo S&P TD 150 with 9000 can filter but after some IC reader input I

"scrubbed" this idea. Appericate your take as well as anyone else who

would like to comment.

 

[rasputin]

Thanks for the response, red! Bear with me, you got me a little confused with the way you worded your response, ya jumped around a bit on me when you mentioned the 300 CFM and then the 110 CFM..

Generally you want to do outside exhaust <- Fan -<Light -<Filter. This keeps negative pressure inside the ducting so the smelly air doesn't leak out, however any leaks in will still pick up some smell.

Yep, that's how I have it planned as mentioned in my post. Exhaust out the room, pulling through the hood & filter. It is essentially all one line, the filter is one end, the exhaust hole is the other and the fan & hood are in between. The fan is facing towards the exhaust hole, there is a small run of insulated ducting between the fan and the wall I'm exhausting out. I read you want/need to keep the fan a few inches away from the walls. Should I have the fan right up against the wall blowing out the exhaust hole?

My issues with this design is the sizing of the fans and scubber. You will need around 300 CFM to remove 1000 W of heat from the room. By using a vented hood and remote ballasts and letting the exhaust temperature run 30* above ambient, you can get away with running a 110 CFM through the hood.

The tricky part is to get the right airflow by matching a scrubber and oversizing the fan.

You say a 300 CFM fan is needed to exhaust for 1K light. OK, I have a 360 CFM 6" so I have that much covered, at least.

Then you mention a 110 CFM pulling thru the hood to exhaust the temp? I have a 360 CFM fan that I can use instead of a 110 CFM. Certainly should do the trick, no?

You said the 300 CFM fan could exhaust the 1K but then that a 110 CFM could exhaust it... Fyi, the hood I have is an air coolable hood with 6" vents on each end for this purpose. Also, the ballast is remote, I have it outside of the actual space where the light is. As far as exhaust temps, that is no matter. The area the room is being exhausted too is very large and the temperature of the exhausted air will not present any sort of issue luckily. That the exhausted air doesn't smell is another issue for another thread.

Did you mean to say that the 300 CFM can exhaust the 1K and filter the room and that the 110 could do it as well, provided the 110 is strictly used for cooling the hood & not any filtering?

Rereading it a few times I'm sure I've read it right & not missed anything but it does say two different fans can accomplish the same thing despite being very different fans... Any further clarification would be greatly appreciated, I'm trying my best to make sure this is set-up the proper way.

 

[Sirus]

Thanks for the reply Red. Here is my situation. I can only exhaust out of

the top/back/bottom of the cab. I plan to have 4 4" passive intakes on

the bottom. Cooling the light I won't have a direct path, there will have

to be bends in the ducting. The ambient room temp is 70F. Will the

150CFM Axial fan be able to keep the light cool enough to hold temps

72F-76F? I have 2 6" 2 speed clip-on fans as well. The smallest/quietest

fan/filter combo I can find is the

TD-100S&P TD Series Inline Fan. For 4 inch round duct - 101/97 cfm (high/low).

or...

TD-100XS&P TD Series Inline Fan. For 4 inch round duct - 135/100 cfm (high/low).

and for filter

CAN FILTER 2600 Max CFM:
84 cfm


or...

CAN FILTER 9000 Max CFM: Recirculating
(Scrubbing):
110/400 m³/h
Exhaust:
55/200 m³/h
@ 0.1 sec contact time

I can run this seperatly and exhaust out the back of the cab. What do

you think. All input welcomed

 

[guest 77721]

Hey Rasputin, I can see how I messed you up.

To remove 1000W of heat, you need 300 CFM for a 10* ambient rise in the growbox. The exhaust comes out at +10*F.

Now if you're using a vented hood, that will be the exhaust temps and since the heat is contained in the hood, you can expect a minimal temperature rise in the box.

If we let the exhaust temps run higher let's say 30*F, then the CFM's can drop as low as 100 CFM.

I'm just using a formula CFM = (3.16 x Watts)/(Delta T)

 

[guest 77721]

Hey Sirus,

You lucked out tonight. I graphed the performance of some of the CanFan fans and filters using their data. I also helped out my chums in the Micro and stuck on the S+P TD 100x data and it looks like a really bad combo to go with. The 135 CFM S+P will only put out about 40CFM.

You never told me the size of your light but I would advise against going with a fan/scrubber combination unless you buy them as a matched pair.

Thanks for the reply Red. Here is my situation. I can only exhaust out of

the top/back/bottom of the cab. I plan to have 4 4" passive intakes on

the bottom. Cooling the light I won't have a direct path, there will have

to be bends in the ducting. The ambient room temp is 70F. Will the

150CFM Axial fan be able to keep the light cool enough to hold temps

72F-76F? I have 2 6" 2 speed clip-on fans as well. The smallest/quietest

fan/filter combo I can find is the

TD-100S&P TD Series Inline Fan. For 4 inch round duct - 101/97 cfm (high/low).

or...

TD-100XS&P TD Series Inline Fan. For 4 inch round duct - 135/100 cfm (high/low).

and for filter

CAN FILTER 2600 Max CFM:
84 cfm


or...

CAN FILTER 9000 Max CFM: Recirculating
(Scrubbing):
110/400 m³/h
Exhaust:
55/200 m³/h
@ 0.1 sec contact time

I can run this seperatly and exhaust out the back of the cab. What do

you think. All input welcomed

 

[kiheibuilt]

I'm getting the hang of the ventilation needs for my future micro grow. I am wondering about the importance or need for a carbon scrubber in a separate mother/clone cabinet. Is it necessary or not?