simple ventilation and electrical questions

guess I'll just jump right into em

I'm currently stuffing a 3x3 tent with equipment before I get started growing. I've read a good bit about ventilation and my big question for my set up is will I want to use passive intake or get a separate intake fan? I'll probably be buying another centrifugal fan very soon no matter what, but don't know if I want to use it in this tent or just leave it until a few months down the line when I start filling up a 4x8 tent. In the 3x3 I have an lec 315 (which cannot be air cooled) and an active air 6" 400CFM cetrifugal fan. In my space, noise and smell are big issues. I'm not trying to be stealthy, it's just an agreement that I'll only be allowed to grow if the homeowner (who lives here) is convinced that my grow isn't going to bother her in the slightest. I'm working on a written proposal covering electrical costs, etc. Right now I think the obstacle between me and a green light to grow is noise. I'm thinking of putting the active air into storage til I move and getting one or two max-fans for the quiet. Not saying money is no object, just that if I have to spend an extra 500 in order to get the green light, I'll do it. Also, I haven't bought my carbon filter yet, As long as I have people here looking at my airflow set up, is a can 33 or a can 50 recommended? I got the can 33 in my cart on amazon but I'm afraid it might not be enough to scrub every inkling of smell. I really need the smell gone, I'm allowed to take dabs in the house but not smoke flower- that's how she feels about the smell.

Weighing my options with my current equipment and possibly one more duct fan-
1. I could buy one fan speed controller and turn my exhaust down a little bit to cut down on noise and still use passive intake. Only uses one fan, so it might be kind of quiet.
2. I could buy two fan speed controllers and one fan for intake, and keep them both at 50%. I've spent a lot of time building computers and my personal experience is that a fan at 100% is much much louder than when it's at 95%, and both of those are hurricanes compared to 50%. Is it the same way with duct fans?
Which of these will make less noise? which is better for my ladies? does having negative pressure in the tent make a difference?


second, I was wondering if it's a good thing to open the tent doors or windows during lights on? I know what I just said about smell, but assuming she's gone for the day or whatever. On one hand, it turns a 3x3 space effectively into whatever the size of the room you're in is, so it's probably gonna be closer to ambient temperature in there, but since the tent isn't sealed anymore, and the intake and outtake are probably in the same area, it would neutralize those, and you'd lose a reflective wall around your light. Net gain or net loss?

Third, I can remember from growing years ago that you don't want to overload circuits by plugging too much crap in to one circuit, basically if your room is one circuit and that circuit is rated for 15 amps, if the amperage of all the stuff in the room that's plugged in and on equals more than 15 amps you're gonna blow the circuit. That's my understanding. my questions, assuming I understand all of this correctly, are- what does blow the circuit mean? Just go flip the switch in the fuse box? And does it help to run extension cords all over the house so that the ballast is plugged in in the kitchen, the fans in the bathroom, etc? does it help to run cords across the room so you're using all the outlets instead of just one surge protector? At what point in size/scale/wattage should a grower even concern themselves with these things?

One more electrical question- In trying to put together a proposal to get this going, I've re-done my electrical costs sheet like four times. At this point I've already made a damn excel spreadsheet I can just type in my wattages, it spits out a cost per week in veg and a cost per week in flower. My understanding is that in my city, electricity is on a tier system so your first 500 kwh are one cost, the second 500 kwh are a higher cost, and any power used beyond that is super expensive. to make a convincing proposal, when I do the math for calculating how much my grow will cost I'm always assuming we're on that highest tier, and in excel it rounds it to 16 cents, which is fine, I'm rounding up with all the costs to make a profit for her, an offer she can't refuse.
so if during veg I use 535 watts during lights on (18 hours) and 220 watts during lights off (6 hours) at 16 cents per thousand watts an hour, (.535x1+(.22x6)=10.95 kilowatt hours, 10.95x.16=$1.75 per 24 hours in veg?
Is that math correct?

Also, just a thought, but am I perhaps overdoing it with ventilation? I mean a 3x3x6 is really just 54 cubic feet, Do I really need over 300cfm?

Any and all answers appreciated
And if anybody expresses interest in my excel grow cost calculator I'm happy to upload that.

Hi borbor, a couple of comments/thoughts as I run (2) those LEC's but in a bigger room and have variable speed controllers on both my intake and exhaust.

Intake/exhaust, noise/environmental controls:
While heat is not as big an issue (as compared to hps/HID) with those LEC's. In the space you'll run them you will need to bring cooler air in, exhaust out, and more likely both to maintain your temps/humidity (humidity probably more so when you fill that tent).

Based on the above, imo you'll need decent inline fans and active for both. But with variable controllers on them and low settings they are significantly less noise than just running them full-out. For your space your intake could even be a 4" reducing it further. There are a couple of brands out there that are quieter, you may want to look at that for stealth/noise factors. You can also build or buy "mufflers" to further reduce noise impact. imo 2x 4" quality inline fans would do it, larger on the exhaust if you want to be safe, but it's not a huge area. Mine are 4", around the 400 cfm mark, in a 4x9.5x7' room running 2 of those LEC's + 85w of LED right now for reference.

What I've found running a 4x9.5x7' room, two smaller cabinets and a 2x2 tent, bringing in cooler/drier air is more effective than exhausting to maintain both temps and humidity, I'd recommend an inline fan for incoming air vs. duct booster for your setup.

Odour Control:
I run a small 2x2 tent under my basement stairs and flower in it either for bud or for breeding which is as much smell. I don't even have a carbon filter on that tent, I have a HEPA filter just under the exhaust, and for the last 4 weeks of flowering I keep a 4L ONA bucket slightly open with the HEPA filter fan blowing across it a few feet away. Even in that scenario, with no filter you can't smell anything but a subtle smell of the ONA gel. I think you'd want/need a filter and but my point is that if there's any smell at all beyond the filter, an ONA bucket should take care of any trace smell for sure. In your case since smell is not negotiable I'd go the safe route and buy the bigger filter, they do work well, I run a 4" inline fan/filter, exhaust outside and even with the room full out flowering there's no smell. The first run I did in the room I left it with no filter until about 4 weeks in, then you could smell the air outside if there was no wind, put one on and have never smelled anything outside since.

Related to your question about keeping the tent open. Don't think that's an option. You'll loose the ability to control temps/humidity, you'll stink the place up when you hit full flowering and have little control over managing the smell, even an ONA bucket with an open tent in full flower would be questionable to eliminate smell. it may reduce it but imo not eliminate it.

Electrical:
You're correct, if you have a panel with switches (vs. fuses) all you do is reset it. With fuses they blow and you have to replace them. Either case, that's a dangerous way to operate and running any circuit that continues to trip is a risky and dangerous situation with a very real possibility of an electrical fire. Typically the safest calc is to try and keep the load at 1/2 the rated load on the circuit. Good news is that if you're running the 120v version of those lights, they require 3A, your inline fans will use somewhere around 1A each full out (mine run .65A/70W at their lowest setting which is typically where I run them), your circulation fans will be less than .5A each. So roughly 5-6A will be your normal total load. Don't know if you have a circuit that can be traced to calculate the load and utilize an existing circuit. A single dedicated circuit would cover your needs. You could split them if you have circuits nearby, not sure how crazy she'd be about you running extension chords and if you do, use heavy duty, preferably outdoor rated extension chords. Not the greatest/safest option. Don't know if you're comfortable at all but I wasn't but learned how to run my own circuits and ran 3x 15A circuits into my room (hiring a contractor was not an option, we're not legal here). Doing it yourself would cost next to nothing, $10-15 for a breaker, some cabling and a box/outlet, $40-$50 max. It may help your case too vs. running chords to split the load.

Quick look at the calcs look about right, got a migraine though, head hurst too much for doing math right now - lol

Awesome thanks man, much appreciated. Any opinion on if larger fans at slower speeds are quieter than smaller fans at speeds closer to maximum?

edit-my math is obviously not correct, as there's a smiley face in it

i feel obligated to mention something called 'start up load' when a motor draws more current at start up than the normal running current load.so a 3amp motor might draw 5-8amps or more just to start. i don't know about the fans you're talking about but knowledge is power and if you run your circuit load (15amp breaker) close to the max with lights and fans and air pumps etc. you'll trip a breaker for sure

Thank you! I'm sure I won't be running that much equipment in the very beginning, but I'm trying to make sure safety is always held above all other things

@GroErr do you know of any helpful links for information on wiring your own circuits?
I am very interested in the prospect.

@PKMSTR When I had to do it I found these 2 the most useful, goggled a lot:
This is a link to an existing article
Attaching a .pdf version of the other, when I went to the link the site was taken down since I downloaded it. I print useful stuff to .pdf and file it, came in handy

very awesome thank you so much