Venting Using 2" PVC?

[redtails]

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.

[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.

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.

[bigtopsfinn]

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

[bigsby]

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!

[Hempsouth]

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.

[bigsby]

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.

[EvilCartman]

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.

[bigsby]

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?

[bigsby]

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.

[bigsby]

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.