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Punk#1

Passive intake, Negative pressure and smell

45 posts in this topic

Hi guys and girls,

Just put together my new growdrobe a few weeks ago, Running a 250w HPS, 5" High power RVK, STR Variac fan controller and 5" Rhino pro filter.

Whilst I was putting it all together I read that anywhere from 1.5x - 7x passive intake would be required. I went with 2x and thought if I needed to I could make it bigger.

The problem is my room smells of weed and I thought it was the Rhino filter, having read all the negative reviews so I've just ordered myself a Carboair filter to replace it but after some reading and tinkering I've realised that my passive intake is probably too big thus not creating enough negative pressure.

I've been using the STR fan controller at setting 1 , about 50% power, because I can maintain good temps, about 25c and it stays really quiet but when I crank it to full power at level 5 the smell stops.

So im thinking i need to make my passive intake a lot smaller and after some experimenting, an intake hole of about 9 inches square, Approximately half of the area of my 5" extract seems to be sufficient. My only worry is that temps will now suffer also the lack of air flow won't be great for my plants.

So does anyone have any thoughts on this? Does this intake seem ridiculously small? Is there something I'm missing? Could it still be the Rhino pro? Should i try the Carboair? I've made sure all connections are secure with tape around connection from filter to fan and fan to acoustic ducting so I'm sure no air is being sucked inbetween fan and filter.

Like to hear any thoughts or opinions on this,
Cheers

 

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I've been using the STR fan controller at setting 1 , about 50% power, because I can maintain good temps, about 25c and it stays really quiet but when I crank it to full power at level 5 the smell stops.

 

I think this is your problem mate - at setting 1, it sounds like you aren't removing more air than you are intaking - therefore allowing it to leak out where not airtight. When you increase the fan power, the smell goes. 


Try running on level 2 or 3 and see - i think you'll find the balance and the smell will go. It also sounds like your intake is too small now, so i'd increase that to what it was, or at least twice as big and see if the smell is still there on level 2 or 3.

Edited by Lean Bear
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33 minutes ago, Lean Bear said:

 

I think this is your problem mate - at setting 1, it sounds like you aren't removing more air than you are intaking - therefore allowing it to leak out where not airtight. When you increase the fan power, the smell goes. 


Try running on level 2 or 3 and see - i think you'll find the balance and the smell will go. It also sounds like your intake is too small now, so i'd increase that to what it was, or at least twice as big and see if the smell is still there on level 2 or 3.

 

 

Ok cheers I'll try that. Missus just checked temps for me and she says it's still 25c today. If i can get away with good temps on level 1 do you think it would be ok to stay on that? I'm going to open up the intake more and see at what point the smell starts to appear and then back down a bit from that

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Lots of small holes for passive intake not one big one.  Two inch core drill.

Cover passive intakes with carbon cooker hood filter material.  Make lots of small holes until desired effect is achieved.

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I’m not sure if setting 1 is recommended,

fans are self cooling to stop them overheating and need to be run at minimum 40% I think. 

Setting one is a lot less than that if I remember correctly. Minimum setting 2 you want.

i could be wrong on settings though

Edited by Rampa Green
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I use mine on setting one just fine with passive intake, I can`t see why there would be any extra pressure as it`s passive and no matter how low the setting it is still moving air and creating a negative situation.

 

The only time I could smell weed in my room was if I had two fans daisy chained and they were both 5" and at the same setting, but one fan was adding more air than the other fan could move, I removed the linking ducting and the smell ceased.

 

I`ve had these controllers for over a year without any other smell issues.

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48 minutes ago, Phoenix said:

Lots of small holes for passive intake not one big one.  Two inch core drill.

Cover passive intakes with carbon cooker hood filter material.  Make lots of small holes until desired effect is achieved.

 

Ok cheers, If I can patch up the big 2x hole I made I'll add a few small holes instead.

43 minutes ago, Rampa Green said:

I’m not sure if setting 1 is recommended,

fans are self cooling to stop them overheating and need to be run at minimum 40% I think. 

Setting one is a lot less than that if I remember correctly. Minimum setting 2 you want.

i could be wrong on settings though

Yeah I have read that setting 1 Is 40% on this forum but not sure if would cause any damage or not.

 

21 minutes ago, ratdog said:

I use mine on setting one just fine with passive intake, I can`t see why there would be any extra pressure as it`s passive and no matter how low the setting it is still moving air and creating a negative situation.

 

The only time I could smell weed in my room was if I had two fans daisy chained and they were both 5" and at the same setting, but one fan was adding more air than the other fan could move, I removed the linking ducting and the smell ceased.

 

I`ve had these controllers for over a year without any other smell issues.

 

What size is your passive intake?

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2 hours ago, Punk#1 said:

I've been using the STR fan controller at setting 1 , about 50% power, because I can maintain good temps, about 25c and it stays really quiet but when I crank it to full power at level 5 the smell stops.

Simple answer turn it up deal with the noise either that or the smell.

You dont want to turn it up because its noisy, then get a quieter fan.( TD Silent,Hyper fan stealth)

Rvk's IMO are noisy as fuck no mater what you do with them STR or not.

I sent mine back and got quieter extraction fan along with acoustic ducting and the STR cant even hear even hear outside the door on setting 5.

i actually changed my CF over to Carbo Air from Rhino and was massively disappointed so much nosier i've gone back to my old Filter. just going to weight my cf in future and if they aren't the same or better then the last just send it back.

what happens to your temps on setting 5 ?

gallery_94416_11658_42671.jpeg

is it one of these you have ?

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44 minutes ago, Punk#1 said:

What size is your passive intake?

 

 

It`s the two flaps on a Green Cube 120, they are about just under a square foot each I would say, and I leave the bottom of the door unzipped about 18"

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I think your air circulation fan(s) is pointing at your passive holes & therefore blowing the smelly air out of the intake. Thus when your powerful fan kicks in it creates a greater pressure, cancelling out your air intake fan pressure, keeping the smelly air inside.

 

That is why I always believe a lower power intake fan is better than passive vents. Plus the negative of light leaks of course :yinyang:

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3 hours ago, BarrySHitPeas said:

Simple answer turn it up deal with the noise either that or the smell.

You dont want to turn it up because its noisy, then get a quieter fan.( TD Silent,Hyper fan stealth)

Rvk's IMO are noisy as fuck no mater what you do with them STR or not.

I sent mine back and got quieter extraction fan along with acoustic ducting and the STR cant even hear even hear outside the door on setting 5.

i actually changed my CF over to Carbo Air from Rhino and was massively disappointed so much nosier i've gone back to my old Filter. just going to weight my cf in future and if they aren't the same or better then the last just send it back.

what happens to your temps on setting 5 ?

gallery_94416_11658_42671.jpeg

is it one of these you have ?

Not good to hear about the Carboair, it actually arrived today but I'm keeping it boxed up so that if I can get my problem sorted I can return it relatively hassle free.

Yeah mate that's the one I have.

 

It's not the fan itself which is noisey rather the turbulence as it exits the wardrobe through the acoustic ducting and goes through a 45 degree angle . There is no noise at all at the end of the ducting and the entire thing is much quieter than when I used the cheap acoustic ducting.

If I could get rid of the 45 degree angle I think could easily have it running on setting 2 or 3 and it would still be quiet.

 

3 hours ago, ratdog said:

 

 

It`s the two flaps on a Green Cube 120, they are about just under a square foot each I would say, and I leave the bottom of the door unzipped about 18"

 

What type and size of fan do you run? I'm quite surprised because my intake at the moment is only 40 square inches which must be quite a bit less than 2 square feet yet you don't get any smell

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3 hours ago, AKPOG said:

I think your air circulation fan(s) is pointing at your passive holes & therefore blowing the smelly air out of the intake. Thus when your powerful fan kicks in it creates a greater pressure, cancelling out your air intake fan pressure, keeping the smelly air inside.

 

That is why I always believe a lower power intake fan is better than passive vents. Plus the negative of light leaks of course :yinyang:

 

Thanks for the tip bud, but I don't use a circulation fan at the moment. I know I should just haven't got round to it yet

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3 minutes ago, Punk#1 said:

What type and size of fan do you run?

 

 

5" Ruck

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34 minutes ago, ratdog said:

 

 

5" Ruck

 

Interesting. 2 square feet works out to 288 square inches, I seem to work that out at 15x passive intake lol

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11 minutes ago, Punk#1 said:

 

Interesting. 2 square feet works out to 288 square inches, I seem to work that out at 15x passive intake lol

 

 

I did say just under and that`s not including the fact I leave the bottom of my door unzipped lol

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