Fan direction question for a DIY hood..

[rsd]

Wanted to chime in the this fan thing.
My company has spent alot of time/money researching air cooled electronics. Here is what my crew has found... of course they did a little more work with the techno-talk that bores me.
Blowing air in:
Pro's- 98% of the fans capabilities are used. In otherwords, less cavitation. Core temperature of the fan remained lower. Core temperature of the machine lower by 18% than "vacuum method". Longer fan life.
Con's- uncontrolled air exit (air will leave by easiest route rather than where directed). Increased internal air pollution (solved by adding thin layer of air filter at intake...did this for my hood). Build up of "dust" from increased air polution. (solved with filter)
Vacuum meathod
Pro's- less internal air polution. Less build up of "dust" resulting in point-source heat build up. No filter necessary (our electronics do not give up emmissions... your tank will!).
Con's- 35% capacity of fan could be used. Far too much fan cavitation. Increased noise/vibration due to cavitation. Increased core temperature of fan by 40%. Unstable core temp of machine (wide fluctuation). Decreased fan life due vidration and burning of electronic brushes.
My Opinion: there is a reason we pump water into our tanks and not suck it out. Water/air will move with the path of least resistance. Pumps create a very small vacuum to create momentum and then the water level adds pressure. If not the pump sucks air and cavitates or simply does not move as much water as it can. Fans/pumps can act as vacuums...but not efficiently. I.E. a pump will pump water up hill at 70gph... but if it were to pump it down hill with the water above it... more like 80-100gph without working as hard.
Just my $.02

 

[jlem]

All of the canopied that I have seen or built have open backs. If the back of the canopy is open then why would their be any noticable pressurisation?:notsure:

 

[harlequinnut]

Originally posted by jlem
All of the canopied that I have seen or built have open backs. If the back of the canopy is open then why would their be any noticable pressurisation?:notsure:
Same here. Mine is open back also with 2 fans blowing in from the side.

 

[bang guy]

RSD - Thank you for sharing.
I have just one more addition that relates directly to aquariums vs electronics.
With Aquariums we could care less where the air exits. Most hoods have an open back where air can easily escape. I don't undertand how the hood could become significantly pressurized. The most important point for aquariums is pointing the fan at the WATER if you want to cool off the water and point the fan at the BULBS if you want to extend the life of flourescent bulbs. If you have MH then always point the fan at the water as MH are more efficient at higher temps.
Bang

 

[bluedolphi]

We are talking about evacuation of air to cool an environment/enclosure. I know that it seems reasonable to think that blowing cooler air into an area would efficiently cool that area, as opposed to drawing the hot air out of that area. Not so.
Sorry but you are wrong. Hey... do any of you have a laptop? Which way is the fan blowing? Its not.... its sucking the air OUT of your laptop case. Why? I already explained it to you. I continue to give electronics as an example, as this is a component that often uses a fan(s) to reduce temperatures from inside an enclosure. In fact light housings are electronic components.
Do any of you have high end amplifiers (home theater for instance)? Which way is the air blowing on your high end amplifiers case? Its not blowing..... is it? Its sucking HOT air out of the amplifier case.
A fan drawing air from an enclosure causing cavitation? Gross cavitation (higher noise) would be the last thing wanted, or acceptable. The manufacturers of expensive high end components would have agreed that the higher noise level (cavitation), was worth the increase in lower temps. Think about that. That in itself speaks volumes. The cavitation is offset by outside air pressure entering the case/enclosure, and is not an issue. But rather a desired effect as it draws the outside air in efficiently. The dust and lint build up of NOT having the fan blowing air in, is just another bonus. Drawing CO2 and other airborn contaminants /corrosives out of a hood is just yet another bonus effect.
Anyone who really understands and is qualified to chime in....
knows better. And also knows that removing the hot air from an enclosure, by drawing it out, is far more efficient, and creates lower temps, in said environment.
Do not confuse water flow with air flow. Cavitating a water pump is a result of the inability of a pump to obtain water from its input (wrong diam., plumbing used for input for instance). A water pump does not actually "push" water. It has an "impellar". It draws water/pulls water/sucks water via an "impellar". The output is actually a biproduct of its action. Jet boat anyone? Swimming pool?
Why is air temperature lower (below freezing at altitude), even though closer to a heat source (the sun)? If you fly you know this. Again its the evacuation of hot/warm air. No... not because of distance from the sun or less sunlight (you should know that there is snow even at the equator - Hawaii for instance). Not because wind is blowing. But because the heat is being drawn away (in this example due to differing air pressure). This is a non mechanical example.
Anyhoooo..... do as you will. I promise not to continue the debate.

 

[broomer5]

I'll toss in my opinion.
Please realize this is just an opinion. I haven't done any tests to support it.
Our goal is to provide intense lighting for our reef tanks.
The lamps get hot - there's no way to prevent this.
Our concern then is to keep the heated air inside the canopy from heating the water surface.
We know that water evaporating at the surface will cool the water. We know that the water will be heated by the lighting - no matter how the air is moving within the canopy.
The question always comes up "how should the fans be mounted - blowing in or blowing air out" ?
I chose to mount the fans in the top of the canopy - each blowing out and up ~ allowing cooler ambient room temperature air to be drawn into the enclosure ~ past the lamps ~ and drawn up.
It "exhausts" out the top.
Heat rises.
You want to get the hot air inside the hood OUT ~ not just blowing around inside. Forcing air INTO the hood does not help to keep it from reaching the water surface.
It moves the air - but it doesn't move the air up and away from the water surface near as well as having the fan(s) mounted to blow out.
Water's going to evaporate no matter how you have them mounted ~ so there will always be some degree of a water cooling effect. It just seems to make sense to me to keep as much of this warm air from actually reaching the water surface.
If we don't heat the water excessively - we should not have to have excessive evaporation required.
I do think that each canopy design, lamp selection, wattage, ambient room temperature, water circulation and fan placement .... along with other factors will affect each set up.
Especially when dealing with water temperature.
Each of us choose how we do it - and in most cases - we accept our choice and the results. Sometimes we think it's the best way, but as I said earlier ~ I've never tried it with fans blowing in.
I'm sure that works well too - but I think blowing out is a better approach for me.

 

[bang guy]

Originally posted by BlueDolphi
We are talking about evacuation of air to cool an environment/enclosure.
As I stated, if your goal is to remove the hot air from the canopy you're probably right.
For most people this is not the goal. Most people want to cool the water. Believe it or not, very little of the heat in the air in a canopy is transferred to the water. The light energy itself transfers a fair amount of heat. To remove this heat you need to cool the water. Pointing the fans at the water cools it better than any other method in my experience.
Since you insist that I'm wrong all I can assume is that you haven't actually done it yourself. I have... many times. Pointing the fan to blow air across the water lowers the water temp 5 - 8 degrees F (depending on relative humidity in the house). Pulling the hot air out of the canopy lowers the water temp 1 or 2 degrees F in my experience.
If your experience with an aquarium differs then I would love to hear about it but I see no correlation between cooling electronics & cooling aquarium water. Electronics don't evaporate as far as I know but that's your area of expertise and you would know better.

 

[rsd]

BlueDolphi-
As a Matter of fact, I am using a laptop, and I do own high end ampliphiers. I am senior partner for a our corporation. Our company currently has five divisions. The first division is a Production service. This division provides audio, lighting, and labor services for events. From arena tours down to speakers on a stick. Such acts as: Cherry Poppin Daddy's, Mark Chesnutt, Verve Pipe, etc...
The second division is a Back-Line rentals company: i.e. drum sets, guitars, keyboards, etc.
The third is "corporate rentals": wireless systems, video rental kits, etc.
The fourth is Communications (installations): night club, casino, church, certified home theater, gov't buildings, all of these types of installs utilize our crew from design to final inspection.
With that said:
QSC 6.0 ampliphier has 2 cooling fans. BOTH push air into the unit with a prefilter. (infact the entire QSC line does)
Crown Macrotech 2400 cooling fans push air into the ampliphier with 2 prefilters running along the bottom front of the ampliphier. (as does EVERY Crown amp)
Creston, AMX, Leviton, NSI control systems all integrate cooling systems that draw cool air from the outside and push the air through the unit. The better systems incorporate a pre filter.
So... to answer your question and chime in. I do understand and I am really qualified.
One last thought: Think of hot air as smoke, especially since smoke is visibly, generally hotter than basic room temperature. When fire fighters what to VENT a room of smoke they bring in large fans with a peice of flexible vent hose attatched. Do they point the fans in to blow the smoke out? Or do they place the fan in the door and point the fan to the street? If evacuating air worked so well... someone should tell the firefighters that. I'm willing to bet they would be interested in learning they have been doing it all wrong.
Perhaps they just don't understand physics and are not qualified.
If needed I can post a pic or two of the inner workings of a couple of amps. I have 6 on our tech bench right now getting cleaned and overhauled for this summer. (especially since they have been used heavily for the past 11 years and still working.)

 

[denny hunter]

Bang Guy, 100% right IMO, I tried it both ways and showed a minus 4 to 5 degree difference in water temp. Saved me from buying a"chiller" or some such equipment ! I am not a "pro" heating and cooling expert like some whom have logged in on this question......

 

[bluedolphi]

RSD.... the firefighter example I have already used to try to make my point. They do not point the fans INTO the enclosure. They evacuate the enclosure by drawing the smoke out of the enclosure.
You did not answer me. What direction are the fans in your laptop. They are not blowing air into the laptop. It is far more efficient to draw the heat out of the case to lower the temperature.
The antiquated designs incorporate prefilters. 11+ years old....
(I am sure you do not feel that an 11 year old piece of equipment should be labeled as antiquated. I'm sorry)

 

[rsd]

You know how I love a light debate.
I have to disagree with both your points. As my father is a former fire commissioner, 2 uncles are in the fire dept. as were my grandfather, and great uncle. Air is forced into a room to evactuate material (not fire, but imputities).
The fan techniques of these ampliphiers is hardly antique. The powerlight series ampliphier is only a couple of years old. The newest digital consoles (i.e. Mackie, Midas, yamaha, Soundcraft) and the newest line of ampliphiers all use induction style fans. Inother words... they still force air into the amps, and yes, they still use a pre-filter.
To answer your question: I have 2 fans in my laptop. The primary fan DOES force air into the laptop. The secondary is used only when the cdr/dvdr drive is running... and yes in too is an induction style fan.
No, this is not an antique. It is a Dell 8600.
In checking on our installation equipment I did find SOME fans that evactuate the air. I had to laugh when the only places I found those are in the lower end models that any one could buy from best buy or Magnolia Hi-fi. These units where removed from an install that was done by one of our cempetitors and continually failed. Which is why they hired us to come make it right.
Also I found the style of fan you talked about on some of the older Peavey amps. These amps are also "shelved" as we consider them to be useless.
But hey, you can do what you want with your tank. I just hate seeing bad advice. The majority of people who ask questions are asking because they are looking for a reliable answer. When someone has not spent the time and money to research a subject they should be objective about responses.
I also find it funny how quickly some people move to making personal attacks rather than bantering about the subject.

 

[rsd]

'Tis all good.
Fortunately your opinion of me makes no bearing on my life, income, or health of my tank. Again, my concern is that of a new hobbiest making decisions based upon mis-information.
As for the fire dept. procedures. I can only comment on what I have seen and the lessons I learned from the firemen I do know. Those lessons being simply: create exits for hot air in a fire (holes in roof etc.) And if you are referring to during a fire.. then yes, you are correct. You do not feed a fire air. But if you are talking about removing contents from a building then I disagree. You do not bring materials over an electric fan.
*** a couple workers found this out the hard way recently when they used a fan to evacuate a dust filled grain sylo. the powder/dust ignited by the fans spark and caused an explosion and fire.
Either way will work fine. Blow air in, suck air out. One is just far more efficient than the other. Arguing over semantics is getting very, very old.
As for your opinion of me, it means very, very little to me as it has no direct impact upon my life.
To those seeking answers to this question... I recommend a little trial and error. You are far better off testing and learning things on your own rather than taking advice over trivial matters... from me OR anyone else. Lesson you can learn on your own are far better than advice taken.
If you will all excuse me I have a little more work to finalize before today ends.

 

[rsd]

what happened to Blue dolphi's reply between my previous posts?
Just wondering?
Good luck to all, and enjoy.

 

[gregvabch]

hey bang, on your tank do you actually have the fans at an angle blowing towards the water, or do you have them mounted towards the bottom of your canopy blowing across?
i'm in the process of building a canopy and i've been tracking the progress of this post. even though beaslbob hasn't chimed in, it's been pretty good.
i however do run a chiller, because my tank is on the 3rd floor of my condo and as everyone knows, heat rises.
i just wanna make sure my chiller isn't working any harder than it has to, since my electric bills are high enough in the summer time as it is.

 

[bang guy]

Hey Greg, In actuality, my current tank has trouble maintaining heat so I have no fans.
My previous tank was in Tucson, Arizona and after some experimentation I angled the fans down slightly to make ripples on the water, I then added another in the sump pointed directly at the water. That work best of all the configurations I've tried.
Warning, this increases evap a LOT but RO/DI water in cheaper than electricity.

 

[stapler]

So Bang...do you have your fans blowing across the water from one side? Is there a vent on the other side....or do you just let air exit the back of the canopy. I will be recieving my 2 fans this week, and would like to do it your way.
Doesnt this thread remind you of the tap water conversations with Bob? LOL

 

[harlequinnut]

Originally posted by RSD
what happened to Blue dolphi's reply between my previous posts?
Just wondering?
Good luck to all, and enjoy.
Either he deleted it himself or a moderator did. :thinking:

 

[bang guy]

Originally posted by stapler
I will be recieving my 2 fans this week, and would like to do it your way.
Just let the air escape through the open back IMO. Experimenting is good though.

 

[stapler]

Will do...thanks BangGuy

 

[gregvabch]

i don't think i'm going to leave the back of my canopy open, that's where i plan on mounting my ballasts. i don't want the lights shining on the wall behind my tank, from the street at night it already looks like im taking bong hits under a blacklight