Lights, Heat, Fans and Venting

[moab44]

I have a new tank with a wood canopy. The back is open. It has 4 48 inch vho lights, with an ice cap 660 ballast. The heat is around 83 to 84 degrees. I am running the lights for 8 hours a day. I have ordered two 4 inch ice cap fans. What is the best option for placement? Should I put them in the back opening? Or cut the roof of the canopy and puy them there? Should I have them both blowing in or both blowing out or one blowing in and one blowing out?
thanks

[poppin_fresh]

If the back is already open, I would be tempted to place a fan at each end of the canopy blowing out. This should allow fresh air in the back, across the lights and out the sides.
.

[lReef lKeeper]

i think that i would have 1 blowing in and 1 blowing out, that will force the air across the bulbs and out the other side. if you have them both blowing in ... it will cause the air to meet in the middle and it will have to find a way out. the later being far less efficient, IMHO.

[CarmieJo]

I think that I have read that blowing our is preferable because it carries the heat away from the tank. If they were in the ends I think cooler air would flow in the back, across the bulbs and be drawn out by the fans. If they were in the top the heat would be exhausted but I don't know if your airflow would be as efficient???

[bbl_nk]

I agree with Bobby...Having one in and out out moves cooler air into the hot chamber and the other pulls it out creating a cross breeze of sorts....

[rayme07]

I think if the fans were on top the air would still come through the back because your still sucking air out so more air has to replace it. But I think the fans on the side would be better it would bring more flow in like put one fan on the side facing in and the other side facing out like a low pressure system in weather the wind brings the high pressure out and the low pressure in tell me if im wrong so i can learn something Thanks
Ray or Raymond wich ever your like to call
me LOL

[bbl_nk]

Good point Ray...I think it comes down to do you want to cut into the canopy. My personal chice would be to run them on the sides for the cross-breeze effect.

[Phurst]

Seems everyone has an opinion

Here's my $.02

I have 2 fans in my canopy, both blowing in. Here's the reasoning. Passing warm, humid, salty air over the fans (this would be fans sucking air out of the canopy) severely shortens their lifespan. Having one blowing in and one blowing out will still pass salty air over one of the fans, plus, you're still only moving the net volume of air one fan alone can move. If your fans blow at 200CFM, you're moving 200CFM of air into the canopy via the blowing fan, and moving 200CFM of air out of the canopy with the sucking fan for a total movement of 200CFM. If, however, you have 2 fans blowing cool air into the canopy, none are subjected to hot salty air, and you're then moving a net of 400CFM through the canopy instead of 200CFM.

[dillan]

my 2 cents now lol i agree with phurst on this one .unless you don't care about the life of the fans and just need to get the maximum amount of heat out of your canopy then since hot air rises i would put em right at the top.

[R. Deschain]

This is all theoretical, since I've only ever had a BioCube, but here's my opinion.

When air is blown in across the surface of the water, it promotes evaporation, which in turn lowers the temperature. Either pointed in or out, air is circulating and water is evaporating. I would think though, if the fans were blowing in, they could be directed more towards the surface of the water.

It'd be cool (no pun intended) if you were to set it up all three ways (in/in, in/out, out/out) to see if there is a difference!

[rayme07]

I agree with phurst on losing the fan to hot salty air and i also agree with Psychojam both good advice.

[CarmieJo]

Here is an article Beat the Heat: Aquarium Cooling Methods by Kevin Kocot - Reefkeeping.com that might be of interest. Here is a question that I don't know the answer to but maybe someone out there does. If not well, we can have some good discussion. I understand the salt and moisture issue but, even with an open back wouldn't fans blowing in tend to force some hot air down at the water and raise the water temperature? Or at least not lower it as much?

[bbl_nk]

Phurst...wouldn't the fans move air either way, similar to flow with a return pump and overflow? If you look at each one individually (one fan at a time), if I installed one regardless of blowing in or out and they are rating at 200CFM, it would push or pull 200CFM. Now adding another one, you are adding another 200 CFM whether push or pull. I would think the only way you would lose the effects of a fan, would be if you had them so close together (probably nearly on top of each other, that they would cancel each other out.

Same theory with a pump and overflow. If I take my pump offline and my overflow lets through 600GPH, I would still have 600 GPH of flow or movement of the water (until of course you ht your siphon break or drain your tank). Likewise, if I plug my overflow and turn on my pump rated at 600GPH, I will get 600GPH flow or water movement until my sump runs dry, right? Now put both online together and I have 600GPH going out, which is water flow in one direction and then 600GPH coming in. Since they are in balance am I not moving 1200GPH?

I'm not a physicist, I just play one on the forum board Just food for thought...anyone know if I am totally off kilter here?

[Phurst]

In practice, you may get slightly more air movement than one fan alone, but you're still moving air out of the canopy as fast as you're moving it in, which would be the equivalent of one fans worth of air moving. If you have one fan blowing in, the air moved by the fan comes out the back of the canopy. If you have one blowing in and one blowing out, you're still moving the same amount of air, it's just coming out the other fan instead of the back of the canopy.

I'm certainly no physicist either
this is just my educated guess.

[Skurvey Dog]

You guys are great and I am a strong supporter of the "think tank" method. I do not have the experience with canopies as others do, but in reading these posts and getting a generalized idea of what everyone's thought are. I too have come up with my own thoughts. And they are only 1 cents worth. The back of the canopy is open, which allows some heat to dissapate. The whole concern of the heat issue in the canopy is an undesireable increase in water temperature. Whether fans are blowing or sucking will allow for heat to be pulled out. Heat rises and I believe that if an air current can create a high flow pattern coming in one end and being "forced" or pulled out of the other end, that would have a greater impact. I think that with air being forced in and not having a direct path, that will tend to have a larger volume or heated area that can come down out of the canopy and heat the water. And as CJO stated, evaporation is a major factor in lowering water temps. Is there a possibility of a fan being used w/o affecting the constant forced flow of air that I suggested above? Or could a fan be used in a sump/fuge area for water movement. I have no fan directed at my water's surface as I use one of my Koralias serveral inches below the surface to move the water for evaporation.

[rayme07]

And they are only 1 cents worth

the smilies do the talking hahaha

Heat rises and I believe that if an air current can create a high flow pattern coming in one end and being "forced" or pulled out of the other end, that would have a greater impact. I think that with air being forced in and not having a direct path, that will tend to have a larger volume or heated area that can come down out of the canopy and heat the water. And as CJO stated, evaporation is a major factor in lowering water temps. Is there a possibility of a fan being used w/o affecting the constant forced flow of air that I suggested above? Or could a fan be used in a sump/fuge area for water movement. I have no fan directed at my water's surface as I use one of my Koralias serveral inches below the surface to move the water for evaporation.

Good point

[PapaMcEuin]

Now for my 4 cents. Pardon the long windedness. The problem is the back is completely open. I am assuming your tank is approx 48 Inches wide based on your light sizes. No fan, no number of fans would do any good unless you mount them all across the front.

I am a IT guy and deal with server room heat issues all the time. What you need is air flow and a fan does not provide that on its own. The "back open" design is to let heat move naturally. In this case, heat escapes from the top of the back and cool air comes in the bottom back. But, you have lots of lights blocking flow from the front to the back.

What I would suggest is two fans mounted on one side of the tank. You need to close off the back of the hood except for a space equal to 1.5 times the size of the fans on the back opposite of the fans. Or you can close off the back completely and make holes on the top opposite of the fans. This will force the air to pass over the lights as it finds its exit point moving the air from cool entrance to hot exit.

Now, that will have one end warmer with the other, so if that puts one end of the tank too much warmer than the other, you can mount 1 or 2 fans on each end, somehow partition the middle and have centrally located vents (top or back).

Ok, now that I have given some suggestions, here is the reason. with a completely open back, fans will give you some cool air in. But, the air will only move over part of the light and then find its fastest way out. Some places will pool hot air which is the same problem as the open back. When your exit space is larger than your input, you have no forced flow, just forced in and lots of eddies and hot air pockets as the incoming air hits obstructions.

Coming in the side and exiting the opposite side/top will use your lights as a linear guide for air flow. Existing the opposite back is just less holes to cut. Opposite side top is likely the best using both natural flow and guided forced flow.

You don't want your exhaust holes to big or you will loose your pressure and loose the flow you are trying to create to move the hot air out. You can always go back and make it bigger, shrinking the size of a hole cut in a tank is a bit more difficult.

As an example, look at pre-built lights that have fans in them. They have a fan on one side and a vent on the other and not vents on the top. Anyway, hope this wasn't too long and you find it helpful.

[rayme07]

good point PapaMcEuin

You don't want your exhaust holes to big or you will loose your pressure and loose the flow you are trying to create to move the hot air out. You can always go back and make it bigger, shrinking the size of a hole cut in a tank is a bit more difficult.

Now on the hole on the back i would build like a draw like door on the back so all you have to do is slide the board to make the hole big or small and if you want to take it off all the way you can and put it back without your tank looking like kids trying to make a canopy for a fish tank and failed in wood shop J/K lol so you dont have the problem with clueing a board if you made the hole to big. Hope this helps
Raymond

[CarmieJo]

Papa, great explanation! Point of clarification, is the fan blowing the cool air in or pulling the hot air out?

[Phurst]

No, no no! You're all wrong and I am right!

LOL, just kidding. There's some great discussion in this thread. Thanks everyone!

[rayme07]

No, no no! You're all wrong and I am right!

NOOOOOO IM RIGHT LOL

There's some great discussion in this thread. Thanks everyone

Your welcome anything to get a good discussions I love alot of discussion its my favorite part about TR
.Raymond

[PapaMcEuin]

Blowing cool air in. As Phurst said first, you don't want to be moving humid salty air over the fan motor no matter how well protected the manufacturer said they protect the fan. Nice fans get pricey. More than one nice fan gets expensive so save the bucks and keep the fans to moving cool clean air in and let the hot humid salty air find its way to the exhuast using the pressurized flow only.

[PapaMcEuin]

good point PapaMcEuin



Now on the hole on the back i would build like a draw like door on the back so all you have to do is slide the board to make the hole big or small

Now that is what I plan on doing between the firebox and smoker barrel on my Barbque pit! It was designed with a big open hole between the two and cooks too fast!

[R. Deschain]

I'll offer some more statements on the topic. My opinions are made with the full authority of a person who is neither a physicist nor a person with experience venting the hood of a reef tank....

I'm not sure the diameter of the exhaust hole would matter. The important factor is the volume of air moving, not the flow rate. If you move the same volume of air through a large hole and a small hole over a given period of time, the air moving through the small hole has to be moving faster.

I didn't think of the eddy current issue, but since the inside of a canopy is a relatively small volume, I wonder what impact this issue would have anyway.

This sounds like a good idea for Mythbusters:the Reef Tank Edition

[rayme07]

Now that I what I plan on doing between the firebox and smoker barrel on my Barbque pit! It was designed with a big open hole between the two and cooks too fast!

yup the more air getting to the coles the faster and hotter it will burn on mine it came with a thing to cover up the holes so this wouldnt happen and it works fine and cooks slow.