Exhaust

[etinarcadiaego]

I have a 400 watt light in a sealed 3 X 2 X 6 room that I'm planing on exhausting with an inline fan. I'm going to buy one fan for exhaust, and one to blow fresh air into the otherwise sealed room. Any ideas on what size CFM I'll need to cool a 400 watter in a space with an ambient temp that is pretty consistently 65 F.

Also, How do you guys run cords outta your sealed rooms? Like, I'll have to drill through the board to run the wires for my sealed reflector out, but how do i then seal the hole? Grommets? Any ideas?

 

[FreezerBoy]

I run cords through the floorboard of the cab, underneath the res shelf. Holes are ¹/₃₂ inch larger than cords, no grommets.

 

[BesideHimself]

Nice chart Freezer.

 

[masterKahn]

Are you using a normal In-line fan or a less powerful in-line duct fan? Is the light in an air cooled hood? Air cooled hoods need much less fan power then a bare bulb and would be better for a sealed room.

Your grow area is 36 cubic feet so after rounding numbers off You would exhaust your entire grow space every 4.5 seconds with a 500CFM fan. I've seen some healthy rooms that had overkill on ventilation and the plants love it. I know some people who aren't happy until a strong vacuum is created in a room that sucks the door shut with a lound thud!

 

[etinarcadiaego]

@ MasterKahn:

I was thinking of using two 6" 435CFM Centrifugal Blower fans, one to exhaust, and one for an intake . . .

My reflecter is sealed and has a 6" hole on both ends for the purpose of exhausting . . .

You think that will be sufficient?

 

[fatigues]

@ MasterKahn:

I was thinking of using two 6" 435CFM Centrifugal Blower fans, one to exhaust, and one for an intake . . .

My reflecter is sealed and has a 6" hole on both ends for the purpose of exhausting . . .

You think that will be sufficient?

For a 400 Watt? YIKES. I think that will be overkill in the extreme.

You want to use two fans:

1) to cool the self-contained Hood/Cool tube; and
2) to pull through a cannister scrubber and otherwise draw air into the room through passive intakes. (You may want to use 2 or 3 8x8 darkroom louvers for your intakes in that space).

If you have any concerns about stealth, running two 435cfm centrifigual Vortex fans is not only VAST overkill, it's going to be very, very loud. (About as stealthy as a Feature Act stripper firing off the Colt .45 that your daddy used in the Big War!)

Depending on where the fans are located in your home, the neighbours may well hear them. . You are very likely to get SICK of hearing those 2 vortex fans, and fast.

If you are running a 400 watt, there is a reflector/hood for that size lamp with a 4" duct, as opposed to using a 6" ducted unit, but they are fairly rare. You already have a 6" airhood - so okay...

In a dedicated air cooled hood, you can probably get away with a 150-200 dedicated to cooling the hood, and another, much less, 110 or so, to otherwise draw air into the room passively and otherwise scrub.

You can get two Panasonic In-Line Whisper fans for this purpose that will be very very quiet.

http://www.iaqsource.com/category.php/whisperline-inline/?category=1029

1 - FV-20NLF1 (240 CFM) for the dedicated hood line, for $140 (this should do very nicely for a 400watt, it's probably a touch of overkill but, not over the top); and
2 - FV-20NLF1 (240 CFM) for the scrubber for another $140. Yes, you could get a FV-10NLFI (120 CFM) for the scrubber, but the cost difference is about $10, and the noise difference between the two is not great (1.0 sones vs. 1.4) so the difference in noise level on the sone scale is about 40%.

You might want to consider getting the 10NLFI however, as it has a 4" duct, and that will recover some grow space (can use a 6" cannister scrubber) instead of a larger 8" scrubber you will have to use with the 20NLFI.

The FV-20NLF1 is 6" ducts, by the way, so it will work with your hood without any reducing on the ducts involved - which is good for both airflow and keeping it uber_quiet.

A normal human conversation at a range of about 3 feet is between 2 and 4 sones in terms of loudness, btw.

Contrast that to the noise level produced by two Vortex 6" inline fans, which are going to be between "yowza" and HOLY SHIT loud.

Panasonic In-Line Whisper Fans for the win! Cool and uber_stealthy. Quieter than many PC Fans. What's not to like about that - especially contrasted to the jet engines you are proposing to install to cool your grow.

 

[etinarcadiaego]

Noise is no concern at all. I was thinking of using 6" 435 CFM fans in case I ever upped to a 600Watt lamp in my room. Would this much air flow hurt the plants in a 36 cubic foot room?

Also, I have no scrubber, as my exhaust is vented outdoors. I'm in a VERY remote area.

 

[masterKahn]

around 900 cfm is way to much for an air cooled hood. With one 6" fan your light should be very cool and able to be inches from plant to glass.

Are you going to run a sealed room for CO2? Passive air intakes are good in most situations. If your sucking the air out new air will rush in to replace it simple science. Exhaust holes high and intakes low for the colder air. Is your Air cooled hood in taking air from outside the grow space? If so the fan for your hood simply has to exhaust the volume of the hood which is very small.

Here is a example for you. I have a 1000 HPS in an air cooled hood. I used a 250 CFM fan to exhaust the hood and a 4 inch in-line duct fan (approx 80cfm) to push air into it. The glass was so cool I could touch it all day long just for fun. This was with a 4" opening BTW, so with 6" openings and even a 600 you should need this amount of air or less. I did this with a $20 inline duct fan and a $50 Stanley blower worked like butter.

 

[etinarcadiaego]

Sorry, not 900 CFM out,

435 in, 435 out.

Non-passive intake . . .

will that be alright?

 

[FreezerBoy]

If you want guaranteed positive pressure and a house that reeks of weed, that will be great. Intake fans are for those who really know their stuff. If you're here asking these questions, you're not one of them. Ditch the intake fan, punch a second 6" intake

 

[Philosophelon]

I definitely agree with Freezer. You only need an intake fan if you are exhausting so much air that a passive intake wouldn't be able to keep up (or would require an impossibly large surface area). There is no reason to move that much air unless you are cooling several thousand watts (even then, passive intake is workable), provided you have the space for a properly designed passive intake. The less resistance experienced by the airstream the better, e.g. large-diameter square ducting with many outlet vents. Although that would probably be overkill in your case .

 

[fatigues]

Noise is no concern at all.

Also, I have no scrubber, as my exhaust is vented outdoors. I'm in a VERY remote area.

Noise may not be a concern re: neighbours, but I expect it will end up being a concern to you.

You can build a DIY scrubber for $40 or so. The plans are in the DIY links. I would highly recommend doing one, even if you are in a very remote area.

All it takes is one unexpected guest or somebody with car trouble during the fifth week of flowering, and that $40 and 30 mins of your time will start looking VERY, VERY cheap.

Venting untreated grow room air is never a good idea. That and hacking power meters is the sort of thing that gets people busted. Every day.

 

[etinarcadiaego]

I have a carbon scrubber that pushes 550 CFM that I plan to put in the same room as my sealed closet, and then exhaust that room air outside about 15 feet off the ground. My home is in a location that doesn't have roads, just gravel paths, and then a long two-track to my driveway which is gated, so there are no visitors here. The cab is a portion of my basement that is closed off with a security door and concrete, so I wouldnT be able to hear the fans from inside or outside, as my g/f can't hear my circular saw running when she's in the kitchen (when i saw in the basement).

The problem I have with passive intake is that it will be intaking air from the room, whereas I wanted to have it intake air from outside. Could I buy a speed controller and just limit the intake fans CFM that way to avoid some of these issues, possible even both fans CFM?

Or is it now wise to intake outside air?

I'm not seeking positive pressure, just neutral, and I know if I move enough air through my cab I get the cab temps close to the outside temps, which would be ideal. Is this not correct?

Why is passive intake better than an active one? Why are intake fans for knowledgeable folk only? Do they cause some kind of problem with the plants?

Thanks for all of your responses so fan, they have been very helpful!

 

[foaf]

intake fans aren't that big of a deal to get right, but the point freezerboy is making is that if your input at any time is in excess of your exhaust then you get positive pressure and you fill your house with the smell of pot. He also points out that good intake holes are all that is really needed. The only benefit of a supply fan that I know of is that you can get good ventilation with a smaller exhaust fan if you also have a small supply fan. Also, depending on how you duct it, you can more specifically direct the fresh cooler air using a supply fan and ducting.

I don't think that it is as critical as some do to perfectly match the two. You need to match the hole size and keep the supply fan with a smaller cfm than the exhaust fan. If the exhaust fan's flow is greater than the supply fan's, it reduces the pressure gradient across the supply fan and you will quickly get a greater flow from the supply fan than what it is rated for, so a too small supply fan can usually keep up with almost any size exhaust fan, as long as the diameter of the holes is the same. A 4" supply fan might limit a 6" exhaust fan instead of help it.

So from a practical standpoint, I like a supply fan with the same diameter as my exhaust fan and about half of the cfm rating. Plus airtight rooms usually aren't, so you get some supply of air from leakage.

Ive always used a small supply fan and I'm sure that it helps to allow good ventilation using a smaller and thereby quieter exhaust fan than you would need if you didn't have a supply fan.

 

[etinarcadiaego]

@ foaf

First off let me say that the grows linked in your sig are SICK!! Seriously, very impressive.

Anyways, I was actually going to use the same fan for the in as the out. Like 2 fans, matched. Both 6" C.A.P. Centrifugal Blower Fans, both connected to the same speed controller so they'd be matched in terms of CFM regardless as to where I have the controller set.

My last question then, is 435CFM enough to cool a 400 WATT lamp in a sealed area? I've had heat issues with a 400 watter before, even when exhausting with a 400CFM fan, but back then I didn't have an aircooled reflector, and I had much higher ambient temps than I will in my current situation. My ambient will be around 65F. Let me know your thought!

 

[foaf]

with an aircooled reflector, the 435 will be more than enough. I think I would just start with an exhaust fan and keep the other blower on the side, it wont likely be needed.

 

[Philosophelon]

If you want to intake outside air, then it will be much easier if you use an intake blower. If you are bringing outside air in through your intake, make sure to use a filter so that you don't bring in pests, spores, etc. I would recommend getting two of the same fan, and putting the intake blower on a speed controller. Then dial back the intake blower speed until you have very slight negative pressure. This will prevent smell from leaking out of your room. You don't want too much negative pressure, though, because it reduces the efficiency of your exhaust fan.

 

[etinarcadiaego]

Not sure if you read my earlier post, but I am using inline blower fans, 2 of the exact same make/model. if i use a filter for the intake fan, will it slow it down significantly? What kind of filter should I use for the intake?

 

[Philosophelon]

I reread your first post. Since you are not using a carbon filter on your exhaust, you may not need a speed controller for your intake fan, provided your exhaust fan is operating under less static pressure than your intake fan.

A filter will reduce airflow through your intake fan (serving the same purpose as a speed controller), but as long as the filter has a relatively large surface area, not by a whole lot.

I used to build my own filter boxes and use disposable forced-air furnace filters (HEPA are better than the regular ones, but more expensive). Now days you can buy HEPA filters at growshops that attach directly to round ducting (they look like an air filter in a car) -- I've never used them, but I imagine they work just fine, as it seems difficult to fuck up an intake filter. They are much more expensive than furnace filters though. Another type of air filter that attaches directly to round ducting are called Air Sox, I don't think they are HEPA, but they are cheaper than the HEPA filters. I should note that I've not used those either, but again, it's just an intake filter, so it's hard to imagine it not working OK.

My main concern with the intake filters I've not used is how long they last before they must be replaced. I replaced my furnace filters pretty regularly, and if you use expensive filters, it may be cost-prohibitive if they need to be changed too often. I think the expensive HEPA filters are washable, but I don't know about Air Sox.

 

[etinarcadiaego]

Thanks for the tips man. I'll look into those. If I may ask, what were you paying for the disposable furnace filters?