Venting Using 2" PVC?

My first post here. Love this site. Tons of great info. I've spent the past couple of weeks reading and searching to pick up knowledge. I see a lot of posts here that could be answered with a simple search. I believing in doing homework before asking questions! That said, here is my case. I'm looking for a little help setting up my grow room. Here is what I've got.

Basement set up. Good climate control all year round. Ready access to electric and H20. Lockable and away from all utilities and systems that might need to be accessed. It's an A- on the rhizome scale. I'm planning a 3'6" x 3'6" x 7' enclosure lit by a 400w dual HPS/MH lighting. I'm going to construct a box and line it with mylar. Stealth is only an issue when it comes to odor and noise (hence the A-). I need to be able to entertain and have the in laws walking around in the living room directly upstairs with no odor and little noise. And naturally I'm concerned with heat from the light. So my issue is venting and scrubbing.

I've read and re-read the AWESOME Noob's Guide put together by rhizome and others. What a great place to start learning. Thanks. So I am familiar with the parameters of venting and scrubbing. I plan a vented hood that will be open to the grow room thereby venting both the light and the room.

My problem is that I only have one way to access an external vent - by tapping into my whole house vacuum exhaust which is 2" PVC piping. I was looking at a hood with a 6" exhaust but I'm now looking for a 4" exhaust hood (do they make a 2" exhaust hood? Would it work?) My thinking is that I will step down from 4" to 2" and out of the house. With a little negative air pressure I should not face any odor issues in the house. I'm not overly concerned with the back yard but don't want it to stink either. I figure that the setup will look like this:

Light hood > 4" exhaust tube > charcoal scrubber > inline fan > 4" exhaust tube >step down to 2" exhaust tube > 2" PVC > Y connector with vacuum vented outside.

Now I'm guessing that I will also need to find some kind of reverse air dam (not sure what it is called) that will go upstream of the Y connector such that the exhaust does not push back up the vacuum system for distribution throughout that house... That would definitely defeat the purpose.

Have any of the gurus here seen or heard of such a setup? Will I face issue stepping down from 4" to 2"? Does this seem feasible? If not I have to move out to a tent in the garage which will be very very limiting. rhizome would give my garage option a b- or perhaps c+...

Any advice appreciate!

Thinking about it a bit more I will also need a reverse air dam on both sides of the Y connector. I wouldn't want the vacuum discharging all over my grow room!

It's called a back draft damper. I can't seem to find a 4" to 2" duct reducer. Damn.

good luck finding anything smaller than 4" for ducting. I have never encountered 2" ventiation ducting of any sorts.

I wish they did make like 2" extraction fans and filters to match for miniature growing environments.

I'm not worried about the fan. It will be a 4" inline fan readily available. My concern is forcing it down to 2" where it meets the PVC. I have found a 4" to 2" reducer but it isn't actually a reducer in the true sense. It is a 4" to 2" PVC bushing and it doesn't reduce - it's an sharp angled reduction (90 degrees). This is going to be a custom job to be sure.

I've refined my rig config a bit:

charcoal scrubber > 4" exhaust duct > Light hood > 4" exhaust duct > inline fan > 4" exhaust duct > damper/draft control > step down to 2" exhaust PVC > Y connector with shared vacuum line > vents outside.

I'm guessing that I will need a speed control unit and that it will be a question of finding the optimal fan speed. Appreciate any help from the board before I go buying components. This is my only hope for external vent.

i don't think it will work going 4" to 2"... what about venting out the enclosure into the basement room?

may i suggest looking into LED lighting as it does not create any heat except about 3-4 degrees...then you might look at an ozonator for the odor....works really well...and quieter than a big fan with a carbon filter~then your 2" pvc would be taking some air out for circulating some air through your box...and some odor out to wherever your exhaust goes!:jointsmile:

Thanks for the feedback. Badly needed here!

bigtopsfinn, what make you think that it won't work? I respect your opinion and I am certainly willing to believe that it won't work but I'd like to confirm with facts or at least conjecture ;). Considering that it is possible to reduce from 6" to 4" why not for 4" to 2"? I realize that there are significant volume differences between 4" and 2" but enough to make it unworkable? What about my idea of using a speed control unit to adjust the air flow? Perhaps it says something that there are no reducers going from 4" to 2"?

stra8outtaWeed, I'm not sold on the LEDs. I've read very mixed reviews. I like the proven technology and results of the HID. I'll do some more reading. Concerning odor control, I have considered other options. My situation calls for 100% reliability. I have to be able to have very uptight work colleagues (including my boss and his boss) directly upstairs on a regular basis. I suppose I could do an internal filter and odor box but I'd MUCH prefer to vent everything out doors.

You raise a good point about fan noise. Can anyone comment on the noise level of inline fans?

Thanks guys. Keep the comments coming.

i am growing with 900w of LED that i did with 2000w of HPS and my weed is much stronger with the LED's...if you get good ones 300w of LED will blow your 400's away! So if you can find some good ones they are well worth it and they pay for themselves in energy savings and no bulbs to buy :thumbsup:

just something to look into with your situation....if your exhaust was bigger then i don't see any issues stopping you but heat could e a problem and only a 2" exhaust!:(

look at my bottom link...that is my LED grow and flower :jointsmile:

Sorry bigsby, it is more conjecture on my part, never tried a 2" exhaust. But I can say that I have a hard enough time maintaining temps on my 400w cab... small ducting, small fan and several bends in the duct make things more difficult.

If you do some calculations, the area of the duct (area of 6, 4 & 2 in. circles) and volume differences (cylinders) reducing from a 6" to 4" and 4" to 2" are pretty significant. You'll have to worry about the fan noise AND the whistling, pressurized exhaust air, and maintaining good temps might also be a problem... There's probably a good reason why 2" ducting isn't produced.

A lot depends on the temps in the basement too. In order to cool that 400w, you'll need a strong fan or cool intake temps (this would most likely require a heater for when the lights are off).

That's why I'm suggesting to keep all the exhaust in the basement if possible. Use a carbon filter in the growroom, and one in the basement room (or some other odor neutralizer). Then there are some instructions online for silencing inline fans, it think you'll be set.

I did a 4" to 3" reducer with 3" ducting and it worked fine, not optimally because of the backpressure that the reducer produced, but it worked. Thing is, I had to use a 130cfm fan to vent a 16 cuft box (2x2x4) because of that backpressure. With the size of area you want to use, I don't think a single 4" fan is going to cut it honestly as they don't really get any higher than 180cfm that I've seen.

OK. You have convinced me and confirmed what I already suspected. 2" isn't going to work it. I've come up with a different solution that isn't as good due to physical constraints but I believe I can make it work. First, please note that I will use a fully enclosed hood with a 4" exhaust so no reduction from 6" to 4" and so no back pressure there.

Consider this: I could enlarge my external exit to accommodate a 4" exhaust and then Y join my 2" vacuum PVC exhaust into the 4" duct. It shouldn't impact my vacuum. So that would give me a 4" exhaust all the way through the system. Will that work for the setup that I'm considering? 3'6" x 3'6" x 7' with 400w HPS.

bigtopsfinn, I have not bought my light yet and I could be sold on the LEDs. I need to do more research. I did read a lot of the LED discussion under the lights thread. It is long, rambling at at times off topic so I'm sure I missed some good info that is tucked away there. A tutorial on this subject is sorely needed. If I go this direction then I'll work on one from a noob perspective. Without violating TOU here, can you point me to some resources? Can you give me some cost estimates to setup a *good* 300w LED system and what components go into a "good" LED setup? I need to know the start up costs. I recognize that there are long term costs savings but the immediate bottom line is important to me. That said, I come from the "do it right the first time" school of thought and would rather pay a bit more up front to have it done right. Any help, pointers, resources you can offer in this regard appreciated.

redtails, I have seen 4" inline at 178 cfm although I'd prefer to keep it a bit smaller for noise issues. Does the fact that I am not reducing under my new 4" straight through exhaust scenario change the equation? Can anyone comment further on whistling / fan noise issues?

I guess I need to go back and do more research on these fan issues. I'll report anything I find here.

Thanks for the input.

Stra8outtaWeed's got some of the best LED nugs I've seen, check out his grow log, it's quite informative.

OK so I looked through stra8outtaWeed's setup. Woah. That is awesome. But the $$ are a bit beyond me. I'm strictly hobby here ;) and although the long life low energy costs appeal, I'm not sure I'll be growing in 10 years. Actually, strike that on account of the last 20 years...

That said, I'd be very interested to know what it would take to light my room with LED. My dimensions are considerably smaller than stra8outtaWeed's. 3'6" x 3'6". I could go to 4' x 4' or downward to 3' x 3' or rectangular or whatever. I'm building for scratch with few restraints. My goal is to get 3 or perhaps 4 good size plants per grow.

What kind of LED array would this require? What would you estimate the start up costs for the lighting (done right). Note that I could build my own array if it results in significant savings but would prefer an off-the-shelf solution. I would still vent but only for odor which is certainly appealing. Thing is, I can do my entire setup for $500 - $600 using an HID. I'm guessing an LED setup will be considerably more (at least in the short term).

Sell me on this setup. I'm half way there. Would I need side lighting? How do you light the bottom of your plants or do the LEDs penetrate far enough? If I go this route I'll do a good grow log and noob tutorial for the community here. Thanks for support!

bigsby,

You need to find out what the static pressure curve for the fan is, the higher the static pressure available by your fan the more flow you have with elbows & reducers. 2" would work with the proper fan but you would have noise to deal with, I bought a used combustion fan off a furnace that vents thru PVC pipe and it cools my 400W, I ran 4" aluminum flex to the fan inlet and 2" tube exhausting outside.

My fan delivers 60cfm under these conditions, I do not have a carbon scrubber so it I was to hook one up my air flow would go down.

Hempsouth, that's interesting to hear. My PVC setup would only involve 1 elbow about 2 feet from the exit. It is a very short run to the external vent. I can not seem to find the 4" to 2" reducer except to use a jerry rigged 4" to 2" bushing. I have significant preference for the 4" to 2" reducer scenario as it involves significantly less work / changes to the current exhaust configuration. Clearly I need to do a bit more homework on this.

Quote:

---

Originally Posted by bigsby

OK. You have convinced me and confirmed what I already suspected. 2" isn't going to work it. I've come up with a different solution that isn't as good due to physical constraints but I believe I can make it work. First, please note that I will use a fully enclosed hood with a 4" exhaust so no reduction from 6" to 4" and so no back pressure there.

Consider this: I could enlarge my external exit to accommodate a 4" exhaust and then Y join my 2" vacuum PVC exhaust into the 4" duct. It shouldn't impact my vacuum. So that would give me a 4" exhaust all the way through the system. Will that work for the setup that I'm considering? 3'6" x 3'6" x 7' with 400w HPS.

---

Good to see that you have the option of going with the 4" duct. As long as your incoming air is a few degrees below your target temp, you should be fine. The 2" ducting and hardware is for specialized applications, you ain't gonna find it at the local hardware store. Besides being kinda pricey, a single 2" line is really on the ragged edge as far as venting a 400 HPS. But, you've already figured that out. ;)

For sheer stealth, albeit at a significantly larger initial investment, LED has some undeniable advantages. You still need to vent, but you can get away with using fans that are significantly quieter than a 4" inline.

Back to the lighting question. The reduced heat is looking more and more attractive. Greatly helps the vent question obviously.

I found this 300w array:
Sell led hydroponic light(300W)

Would this work for my needs? I'm guessing yes. It claims to be equivalent of a 600w HID. I can't find a distributor in the US or price info. Any help?

These LED considerations are veering badly off topic. In the interest of consolidating formation for others I'm going to move my LED questions to a suitable place. Let me figure out where it belongs and I'll post the link.

Man that 10 minute timeout on edits sucks.

Rather than hijacking str8's grow log with my questions I've moved the LED discussion here:

http://boards.cannabis.com/indoor-li...ml#post2085365

Your continued input appreciated!

I'm still working through my venting issues and will continue to do so here.

Check out LED site: growitled.com this guy has some great stuff

You might be able to go from 4" to 3" and then bush down from 3" to the 2".

My components are metal vacuum tubing, maybe look at muffler pipe at JC Whitney or something comparable. One thing I failded to mention is I had to put a glass lense cover in my light hood for the small fan to vent properly.

Quote:

---

Originally Posted by bigtopsfinn

Stra8outtaWeed's got some of the best LED nugs I've seen, check out his grow log, it's quite informative.

---

thanks BTF~ i appreciate the comment...tried to send more rep your way...when it lets me :thumbsup:

I'm putting my venting issue on hold while I determine my lights. I'm being tempted by the LED option. No heat means I could just scrub and exhaust to the adjoining room without need for vent. I many still make use of the 2 inch PVC to pull in fresh air but not sure.

If I can do LED right at a reasonable price then I'll likely go that route. If not, I'll be back here working out my venting issue.

I think you'll do fine with a 400 HPS as they do not put out that much heat, at least nothing that a small AC can't handle. You'll have to do some construction for the ventilation system. Remember your babies need fresh air as well as exhaust, 2 inches in most cases will not work. Also take into consideration future upgrades if this cycle goes well.

I know it's a basement but don't you have a window or something? I wouldn't use the house ventilation or vacuum system in conjunction with your grow, isolate the two so there is zero chance of odor escaping.

What are your relative humidity levels in the basement?:rastasmoke:

It's a killer. I have tied myself in knots over the venting issue. I'm leaning towards venting into an adjacent room using a carbon scrubber together with an ozonator or two. Widening my 2" PVC pipe to 4" will be all kinds of hassle. It can be done but it would require joining with the vacuum exhaust. No windows in my grow room. There are windows in the adjacent room and I would leave them open to get some fresh air but the plants will have to do with the relatively stale air in the basement. Of course, I plan to include a few intake vents but these will be drawing air from the basement. I can't say what the relative humidity is precisely. I would imagine it is on the higher side depending on the time of year without a great deal of fluctuation from day to day. I do not want to get into AC issues if it can be avoided. Thoughts on this issue appreciated.

Less than ideal I know but these are the conditions that I'm working with. Vent and other construction issues are not a problem. I can build whatever I need.

Thanks for the input.

I don't want to confuse you more, and this is not typical advice for a new grower, but have you considered a 'sealed room'? That is, no exhaust, no intake... you need heat, perfect humidity, plenty of light and co2 for that though, and everything must be dialed in: http://boards.cannabis.com/advanced-...ent-guide.html

Just wanted to throw it out there as an option, and the guide is a good read anyways. This will cost some $$$, but it's probably worth it for the peace of mind and superb growth. :jointsmile:

use a venturi to suck the air out of the room with 2" air inlet and 500 gph rated pump with a narrow throat venturi design

A sealed grow room, eh? Interesting but I need to keep it simple. I'm taking on quite a bit as it is and feel that dealing with that many issues would be overwhelming.

I've settled on my strategy for venting and odor control - a good 6" carbon scrubber vented to an adjacent room with an ozonator in the vent room. I can also place one elsewhere in the house if needed. My intake will have to be passive with some fresh air coming from a window located elsewhere in the basement. I am going to eliminate the external vent all together. Making it work would be too destructive/disruptive with the other utilities that are currently utilizing the space - whole house vacuum exhaust, 2x electrical out, and gas line for the grill. Upgrading the vent to 4" could be accomplished with considerable work but risks to the vacuum. Scrubbing and venting interior to the house makes the most sense. If I face odor issues then I'll take the steps needed to vent externally at that time.

Following the advice of someone here I have settled on my grow room particulars / strategies. Now I'm gathering the materials. I'm still not ready to build so I'm just planning, reading, learning. I'm going to do a scrog setup. I've increased my room size so that I can work comfortably around the scrog. The scrog will be 32" x 54" and I will be looking to put 4 plants under the screen. My room size will be 6'W x 5'L x 6'6"H. I'd like to have the option of expanding the size of the scrog in the future hence the room size. The room will be wood frame construction with drywall, although I am considering other wall board construction due to humidity issues. Thoughts welcome. I will create a mylar box to enclose my scrog.

Thanks for all the help with my venting setup. Any thoughts on the strategy outline appreciated. Recs on carbon scrubbers too!