Most efficient way to cool 8KW?

[Albert Hofmann]

If you find that more air is being pulled from the 6" elbows/ducts/hoods closest to the fan pulling the air you can install dampers in them and balance the system.

I have dampers in the elbows...look close at the top of the elbows in the bottom pic...you can see the damper levers

 

[Guest]

Albert-----OK, the duct works is so shinny that I didn't see them, now I see it inside the elbow, on the right, in the first photo.

Mine uses a 10" round duct manifold system and is highly efficient. The cost isn't that much and the rewards are great.

TyStik

 

[Albert Hofmann]

Yea Ty, they are kinda hiding I have seen pics of your setup and it is fantastic...

 

[BlindDate]

Stealthy....As I understand your post, you are talking about using 12" manifolds with the 8" fans that you already have. Is this correct?

If so, then yes, that is a much better way to do it vs 8" manifolds. And, it leaves the option to upgrade if necessary. Like I said, the area of 4 each 6" diameters is the same as a single 12" diameter. An 8" diameter has only HALF of the air handling capacity. YOUR MANIFOLDS CAN NEVER BE TOO BIG, ONLY TOO SMALL. Look at Albert Hoffman's post, Big Manifold.

No no, you want the manifold ducting to be 8". You want high air pressure and the 8" fans would not create that pressure.
Whatever size your fans are is what size your manifold should be.

The volume of the manifold will have no relation to the pressure developed by the fan unless the manifold is too small. An 8" manifold will cause the lights to pull air unevenly(see above volume comparisons).

 

[Couch Locked]

Most efficient cooling method.

I may sound retarded, but if the ends are capped where is the air coming from? The hoods themselves? If that is the case how would you cool this series if you wanted your A/C hood system completely enclosed.

 

[Albert Hofmann]

Couch Locked - I will assume that you didn't read the whole thread...look at my pics at the top of this page

 

[Mr Celsius]

Stealthy....As I understand your post, you are talking about using 12" manifolds with the 8" fans that you already have. Is this correct?

If so, then yes, that is a much better way to do it vs 8" manifolds. And, it leaves the option to upgrade if necessary. Like I said, the area of 4 each 6" diameters is the same as a single 12" diameter. An 8" diameter has only HALF of the air handling capacity. YOUR MANIFOLDS CAN NEVER BE TOO BIG, ONLY TOO SMALL. Look at Albert Hoffman's post, Big Manifold.


The volume of the manifold will have no relation to the pressure developed by the fan unless the manifold is too small. An 8" manifold will cause the lights to pull air unevenly(see above volume comparisons).

I will concede, you seem to know more then I on the subject. I'm definitely not an HVAC professional, I just know its an efficient system.

I assumed that you would want more pressure and that there is a maximum cfm allow through a certain diameter tubbing. I can't seem to find an inline 8" fan that is over 747 cfm, can an 8" duct handle more cfm?

 

[Albert Hofmann]

Mr. Celsius - 8" rigid duct can definately handle more than 750cfm...but you need to ask yourself how loud do you want your system to be? I went with 10" rigid knowing that if I had to I could collar down a 12" vortex to work with my 10" duct...it will however, be louder. Also, this system works better with only 1 fan pulling...an 8" fan pushing and an 8" fan pulling isn't very efficient since air movement through the system is limited to how much can move through the exhaust (2nd) fan. To increase airflow in this system you need to increase the size of the exhaust fan. Another important thing to remember is to silicone and tape all rigid connections to make your system air tight

 

[BlindDate]

an 8" fan pushing and an 8" fan pulling isn't very efficient since air movement through the system is limited to how much can move through the exhaust (2nd) fan.

Dead straight. And I would add that if he can figure a way to rig both 8" fans on one end he can double his flow rate. Maybe some kind of "Y" connector (see my drawing below).

I assumed that you would want more pressure and that there is a maximum cfm allow through a certain diameter tubbing.

Think about this:::: If a centrifugal fan is running free, with no ducting whatsoever attached, that is the highest possible flow you are going to get out of the thing. Once you start restricting flow, pressure increases and flow decreases. Pressure is not going to cool our lights, it's AIR FLOW that we desire. The larger the ducting, the less restrictive, the less friction, the faster the flow. It's really simple, go with big ducts.

Now lets talk about pushing and pulling air: If ducts are big and open a single fan on one end is all that is required. Sure,,two fans inline will produce more pressure, but if you NEED to produce pressure in order to get more flow then, again, your ducts are restricting, understand?

 

[Mr Celsius]

4 - 6" outlets from the manifold would cause pressure?

 

[BlindDate]

4 - 6" outlets from the manifold would cause pressure?

No, but 4-6" outlets going into a 8" manifold will.

4-6" outlets = 113 square inches

1-8" manifold = 50 square inches

So you can see the bottle neck is at the manifold in this case.

vs

1-12" manifold = 113 square inches

 

[BlindDate]

Say, can someone please tell me how to post an image such that it shows up full size rather than as a click-on?

Thanx

 

[Mr Celsius]

Thanks blind, I get it.

You would right click on the image and copy the image location and copy/paste it into your text. Or if you're hosting it from your gallery, goto your gallery and click on the image. It will have tags that you can copy and paste below it.

 

[Stealthy]

Stealthy....As I understand your post, you are talking about using 12" manifolds with the 8" fans that you already have. Is this correct?

If so, then yes, that is a much better way to do it vs 8" manifolds. And, it leaves the option to upgrade if necessary. Like I said, the area of 4 each 6" diameters is the same as a single 12" diameter. An 8" diameter has only HALF of the air handling capacity. YOUR MANIFOLDS CAN NEVER BE TOO BIG, ONLY TOO SMALL. Look at Albert Hoffman's post, Big Manifold.


The volume of the manifold will have no relation to the pressure developed by the fan unless the manifold is too small. An 8" manifold will cause the lights to pull air unevenly(see above volume comparisons).

BlindDate,
Yes, I would be enterintering the room (through the ceiling /attic) with 8" insulated duct. I would then attach it to some type of manifold that in turn feeds 4 rows with 2 - 1000 watters in each row...from there the air gets fed through the lights into a manifold at the opposite end.
I'm trying to figure out what size manifold...so your saying the 12" manifold would work better then the 8" manifold if using my 8" fan?
Also, I think that last pic you posted is a great idea but don't you think this would work about the same?



Does the manifold idea work better then the above pic because it allows for all lights to get the same amount of air flow AND the temperature of the air is the same across all lights.
If it were in a straight line (like in my above pic) by the time the air reached the last light it would be super heated and not cool as efficiently? Hope I got all of this right.

One more thing...just say I decide to go with 12" fans (one pulling - one pushing using the manifold idea) would it be ok/better to go even bigger with my manifolds like 14" or 16" (incoming duct would be 12")?





Couch Locked,
One fan is pushing air, one is pulling. Only one end of each manifold is capped.

 

[green_tea]

blind date,

with your drawing above (which I like, and personally is a good setup for a number of reasons) how would flow be affected by tons (~2ft on each side of the lights) of flex ducting?

so that each light in your drawing can be raised and lowered individually.
Also if say two of the pairs of lights (that are connected) are up high (late in flowering) and the other two pairs are lower (early in flowering) how would that affect flow in the system? would the two lights that are higher end up getting all the air flow since the ducting on the other two pairs is the more resistant path?

 

[Stealthy]

blind date,

with your drawing above (which I like, and personally is a good setup for a number of reasons) how would flow be affected by tons (~2ft on each side of the lights) of flex ducting?

so that each light in your drawing can be raised and lowered individually.
Also if say two of the pairs of lights (that are connected) are up high (late in flowering) and the other two pairs are lower (early in flowering) how would that affect flow in the system? would the two lights that are higher end up getting all the air flow since the ducting on the other two pairs is the more resistant path?

Don't wanna answer this question for BD but installing dampers on each row so as to limit air flow to particular rows (to even out air flow) may work pretty good for this problem.

 

[Albert Hofmann]

Dampers are exactly how you control airflow to each row...place dampers on the exhaust end of the system. And stealthy, as I stated before, this system does not work with a push fan and a pull fan. 1 fan pulling is the most efficient setup for this system. Air WILL NOT move through the system any more than the exhaust fan will allow.

 

[Stealthy]

Albert Hofmann,
So would this be a better idea then pushing and pulling at the same time?

 

[Albert Hofmann]

Yes, that would definately work better...but I still maintain that 1 12" will be most efficient. You will still have a bottleneck at the 8" Y . Remember that the area of 1 12" duct (113.04 square inches) is greater than the area of 2 8" ducts (50.24 each for a total area of 100.48 square inches).

 

[BlindDate]

Yes, I would be enterintering the room (through the ceiling /attic) with 8" insulated duct.

Bad idea,, again!! 8" duct is the restriction point.

so your saying the 12" manifold would work better then the 8" manifold if using my 8" fan?

Yes, that is exactly what I'm saying.

I think that last pic you posted is a great idea but don't you think this would work about the same?

In terms of air flow, yes it would be almost the same, but, like you understand, by the time the air got to that 4th light it's already pretty damn hot and worthless for cooling.

Does the manifold idea work better then the above pic because it allows for all lights to get the same amount of air flow AND the temperature of the air is the same across all lights.

You got it.

One more thing...just say I decide to go with 12" fans (one pulling - one pushing using the manifold idea) would it be ok/better to go even bigger with my manifolds like 14" or 16" (incoming duct would be 12")?

Another mental setback....so I'll explain it again:

The ONLY purpose of having two fans running in series is to increase pressure, but, if your ducts are sized correctly pressure is NOT needed to get the same amount of flow.

Two fans in series will equal the flow of one fan

Two fans in parallel (like my "Y" drawing) will double the flow.

Yes, that would definately work better...but I still maintain that 1 12" will be most efficient. You will still have a bottleneck at the 8" Y

There is no bottleneck since the 8" Y leads into a 12" duct.