150w HPS Club and Resource Guide......

[Bulénath]

Careful with the math there. Each PC fan is 4 inches squared or 16 square inches.

3 x 16 square inches = 48 square inches

The area of a circle is pi * r ^ 2.

It sounds like you got the r ^ 2 with "4 divided in half, times itself" but left out the part about multiplying it by pi (3.14).

So, a 4 inch circular hole gives you about 12.5 square inches.

4 inch circle: 12.5 square inches
4 inch square: 16 square inches

-Q

You're right, but do you really need to use PI? I am just using the simple short cut. Hence "Surface Value" Opposed to "Surface Area".

 

[Quazi]

Absolutely.

Your results will be very inaccurate if you don't.

Let's look at just how bad it will get with your method, compared to the real method.

1 inch holes:
.25 square inches
or
.785 square inches

2 inch holes:
1 square inch
or
3.14 square inches

6 inch holes:
9 square inches
or
28.26 square inches

As you can see: with your method you're around 300% inaccurate. Which, doesn't make as big a difference in the smaller holes, but as you get bigger, you get much more incorrect.

-Q

 

[Bulénath]

PI is unecessary because we are using the value in the context of a ratio.

I will be the first to admit if I am wrong, but I just don't see it.

Ya know I just hit a fat 18.8 diffused 18" custom roor and about 0.7gs of dank...So I could be stoned...

But I just don't see the neccessity of it. Regardless, even if you cut out PI, the ratio remains exactly the same.

 

[Quazi]

We're using it to calculate the number of holes necessary for intakes to be appropriate considering the size of his exhaust.

PC fans are square to mount flush. He never said that he would be using 4 inch square intakes. He might be thinking of using circular holes that are 1, 2, maybe 5 inches in size. Who knows?

It sounded like you were trying to give advice about finding the area of a particular hole since you were instructing on how to come up with the value. I'm not really sure what you were trying to say with your "surface value" and estimations.

I just knew that they were widely inaccurate compared to actual area.

I was just trying to make sure he had all the information to work with, that's all. :wink:

-Q

 

[Bulénath]

Thats right!!!!

Circles and squares!! ..You are converting circles to squares! It's so obvious now! Hehehehe

I never use squares, only circles. So I don't use PI, it is uneccessary.
PI is only needed if you are converting the actual surface area from square to a circle or vice versa.

But, if you just use holes, the shapes are always the same. You don't need PI in there confusing things up. All you need is the value found in the ratio to find the relevant surface area for exhaust/intake.

 

[hoosierdaddy]

Pi has nothing to do with a square, Bulenath.
What Quazi is telling you is spot on. One may choose to try and use a different method, but they will be off.

Just to make a point, tell me what sort of intake I need to equal two 8" fans at the exhaust? All I have is a 2" hole saw and I need to know how many holes to cut.

?

 

[Bulénath]

I know what PI is.
I am saying if you strictly use circles, you don't need to multiply by PI because no matter how you slice it the value remains the same. I don't care if PI is 3.94 or 4.93, it dosen't matter what value PI is, because it is irrelevant when used in the SOLE context of circles. I am saying PI cancels itself out.

Now if you are using squares AND circles, you will need PI to calculate the surface area of the circle to accurately compare it to the surface area of a square.


Oh and two 8" fans would be (8 divided in half ) = 4 x itself =-16.
16 x 2 fans is a value of 32.

2" hole = (2 divided in half) = 1 x itself = 1.

So you have an intake/exhaust value ratio of 32/2.

In other words you need 32 x 2" intake holes to equal two 8" exhaust holes.

Now if you guys wana complicate things and multiply by 3.14 then go ahead, it dosent change the actual value of 32/2.

 

[Cozy Amnesia]

I see what you're saying Bulenath, that pi will be canceled out in the ratio, but there are other things that need to be factored in too.

2 * exhaust area = intake area
2 * pi * (radius of exhaust)^2 = pi * (radius of intake)^2
2 * (radius of exhaust)^2 = (radius of intake)^2
sqrt(2 * (radius of exhaust)^2) = (radius of intake)
1.4 * radius of exhaust = radius of intake

Explenation:
"The ratio" states that the intake area needs to be twice that of the exhaust, or in other words it takes two exhaust holes to equal the area of the intake hole. I then subistuted area with pi * r^2. pi on the both sides of the equation cancels the other out. To get rid of the exponents, I took the square root of the left side which gave me 1.4 times the radius of the exhaust. What that means is the radius of the intake needs to be 1.4 times the radius of the exhaust, or the exhuast's radius needs to be .7 of the intake's radius. You can't just say that intake's radius/diameter needs to be twice that of the exhaust because it's a square function.

To calculate how many 2" holes you need to double the area of two 8" fans:

2 exhaust holes * (4"^2 * pi) exhuast area per exhaust hole * one intake area per 2 exhaust area * one intake hole per (1"^2 * pi) intake area = 16 intake holes.

You where close blunenath, you just got mixed up somewhere. The reason I included all labels was so you can see that they all cancel each other out except for intake holes. Although I'm not ruling out the possibility that I was the one who made a mistake, I did just flunk a physics exam...

At any rate...

I got all my bud nice and dried up. It didn't take long because my humidity is so low that my digital humidity gauge just says "LO". They're so brittle and dry on the outside, but I think a nice cure will do them a lot of good. The final dry weight is 53.0 grams, or 1.9 ounces. It's not enough to quit my day job, but it will get me torn up for the next couple of months. Thus far they smell like a mixture of orange, kerosene, and apple pie.



Improvements for next time:
-better genetics
-bigger cab
-more light (don't worry, I'm not abandoning you guys) :friends:

 

[hoosierdaddy]

No, Cozy...we were only figuring straight relationship, and not taking into account doubling the intake area. And Bulenath is spot on with the relationship thing. I was actually the one who was confused at what he was trying to convey.

And no, we do NOT need to have double the intake area. It is just a good rule of thumb to follow. It is always best to have more volume available and not used, than not having the volume available.

What we DO need to do is figure for losses at the intake orifice(s) due to friction and back pressures. A well designed central air system in a house will be designed with approx. 10% over sized (from exhaust) intake.
And more holes creates more friction and back pressure than a single hole of the same area. SO, if using small holes, the over sizing needs to be slightly more than it would using a single hole to get the volume. A single hole may need to be over sized by 10%, whereas several holes you would want to go more, say 12-15%.
Although it won't hurt anything, going 50% or more over is simply overkill. It cannot increase the cooling ability at all. Once you get to the oversize point that accounts for the small losses at the intake edges, then you are good.

 

[abirdintheair]

time to add some shine

time to add some shine


banana og and some g13 x burmese

 

[growDaddy]

The final dry weight is 53.0 grams, or 1.9 ounces.

sweet cozy. Some good times ahead for one jayhawk!

 

[guest3589]

Nice harvest Cozy, looking good abirdintheair, it's inspiring to seee what you guys are pulling off with the 150's.

 

[growDaddy]

Today is day 57 for my girls. I will turn of everything today and harvest Monday.
These are from my 150w HPS grow. I also have 6 55w CFLs for a little help!

 

[Quazi]

Nice growDaddy! That looks like some awesome smoke.

Harvest Monday huh? Bet you're excited! I'm just a week behind you so I'm definitely feeling the excitement.

And yes: Bul is correct. When dealing strictly with circles, the 3.14 can be removed.

This because it is a constant in the equation when talking about circles:
A = pi * r ^ 2

So yes: Bul was correct that his ratio could be used if you're only talking about comparing circles to circles.

Cozy, I'm so stoked that you're harvesting man. I remember back when you were first getting started! Nice to know those plants didn't overgrow ya. Looked like they might for a couple weeks in there.

150s rule!

-Q

 

[growDaddy]

Nice growDaddy! That looks like some awesome smoke.
Harvest Monday huh? Bet you're excited! I'm just a week behind you so I'm definitely feeling the excitement.

150s rule!

-Q

I am so excited I can hardly stand it. I haven't harvested any I grew for a long time (1968) and that was some we planted in spring and came back in the fall and cut them down.

King Harvest has surly come!

 

[hoosierdaddy]

Glad you got that feelin again, growdaddy! Aint nuthin like it.

 

[Cozy Amnesia]

Thanks all for the positive feedback, growDaddy those are looking real tasty!

No, Cozy...we were only figuring straight relationship, and not taking into account doubling the intake area. And Bulenath is spot on with the relationship thing. I was actually the one who was confused at what he was trying to convey.

And no, we do NOT need to have double the intake area. It is just a good rule of thumb to follow. It is always best to have more volume available and not used, than not having the volume available.

What we DO need to do is figure for losses at the intake orifice(s) due to friction and back pressures. A well designed central air system in a house will be designed with approx. 10% over sized (from exhaust) intake.
And more holes creates more friction and back pressure than a single hole of the same area. SO, if using small holes, the over sizing needs to be slightly more than it would using a single hole to get the volume. A single hole may need to be over sized by 10%, whereas several holes you would want to go more, say 12-15%.
Although it won't hurt anything, going 50% or more over is simply overkill. It cannot increase the cooling ability at all. Once you get to the oversize point that accounts for the small losses at the intake edges, then you are good.

Then you would need ~37 2" diameter holes to be 115% of two 8" fans. And 32 holes to equal the fans. To double the area, I should have been multiplying by two and not dividing by, no wonder I failed that exam...

 

[Bulénath]

Nice plants grow daddy!
I can't wait to hear the total harvest weight!

I agree that the intake needs to be larger than the exhaust...
The larger the better, until you hit roughly 2x larger, then that is about enough.
An intake 1.50 times larger makes a big difference compared to 1.15 x larger
Besides, sometimes when you stuff your cabinet full of pots, some of the intake holes are blocked. So shoot for 1.50 times bigger if it doesn't screw up your floor plan.
Also, the larger the intake the quieter the exhaust, the better the dispersion of fresh air, and the less over all static pressure.

Is it just me or does smoking ganja blunt mathematical skills the most?
I swear that when I am high math is the hardest thing to follow...

 

[OahuGrown]

Im looking for ventilation for my cab with a 150 Hps.
My cab is 4 feet tall and 20" x 16".
I was think of using this :
http://www.laskoproducts.com/fans/model_4904.html

Does anyone know how strong it is?

 

[Cozy Amnesia]

Im looking for ventilation for my cab with a 150 Hps.
My cab is 4 feet tall and 20" x 16".
I was think of using this :
http://www.laskoproducts.com/fans/model_4904.html

Does anyone know how strong it is?

Many growers have used this style of fan with the 150w, but I mainly see the bigger one being used. Gather up the extra $15 or so and spring for the bigger one. I have yet to hear somebody complain about their performance, which tells me that these are good fans.