Hi there I have a 30gal 4ft long that is lit by 4x54w t5 bulbs. I am getting tempt ure rise when the lights are on and am looking to put some fans into the canopy but unsure how many and placement. Some say pointing straight down vertical onto the water surface and some say to blow air across the water so in one side out the other size of the hood. What's your views and experience's. Thanks Ian
Canopy cooling
- Thread starter rado87
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o2manyfish
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Getting the heat out of the hood is one step. In the old days I bought 220v computer muffin fans and ran them at 110v so they ran silently. But there are lots of silent fan options available now. Using one on each end of the canopy in a push pull method would work well.
Aiming a fan at the water, will definitely keep the tank cool. This results in evaporative cooling which is very effective. My system is 1100g and 700gallons is outside in my yard. When we get 110 weather I am able to keep the entire system cool using a pair of $12 box fans blowing air across the surface of the sump and the frag tanks. We just went through a 10 day period of triple digit weather and my system never went over 80.5 degrees.
However, there is a caveat... Evaporative cooling does a lot of evaporating. So you have to have a top off system to replace the water evaporated off so that you don't have salinity swings. My system can evaporate up to 50g a day during the heat of the summer. I top off with Kalkwasser, so for me with a heavy coral load the evaporative cooling is a great for helping me keep my levels up.
Dave B
Aiming a fan at the water, will definitely keep the tank cool. This results in evaporative cooling which is very effective. My system is 1100g and 700gallons is outside in my yard. When we get 110 weather I am able to keep the entire system cool using a pair of $12 box fans blowing air across the surface of the sump and the frag tanks. We just went through a 10 day period of triple digit weather and my system never went over 80.5 degrees.
However, there is a caveat... Evaporative cooling does a lot of evaporating. So you have to have a top off system to replace the water evaporated off so that you don't have salinity swings. My system can evaporate up to 50g a day during the heat of the summer. I top off with Kalkwasser, so for me with a heavy coral load the evaporative cooling is a great for helping me keep my levels up.
Dave B
I have a auto top up atm and loose about a litre a day now with the enclosed top. Would a fan inside the canopy clipped onto the tank in increase evaporation or do I need to pull in cooler air first or will recycling the air in the canopy to blow directly at the water surface.
o2manyfish
Valuable Member
The more air you blow directly at the surface the more evaporation you will get. If you are just pulling air in one of the canopy and out the other end, you will get a slight increase in evaporation.
Now if you are going to aim a fan directly at the tank surface, you still want to ventilate your hood. Because the evaporation and salt creep will go crazy inside your hood. And as the humidity in the canopy goes up the effectiveness of the evaporative cooling goes down.
Did that answer your question?
Dave
Now if you are going to aim a fan directly at the tank surface, you still want to ventilate your hood. Because the evaporation and salt creep will go crazy inside your hood. And as the humidity in the canopy goes up the effectiveness of the evaporative cooling goes down.
Did that answer your question?
Dave
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I think I have that same fan from Walmart (in white), but what I did was to take off the "clamp-on" part, drill a hole to just fit the fan, and zip-tie the fan in place:
I have found if the canopy is enclosed or mostly enclosed, two 120mm computer fans, one in each end down closer to the water surface and both blowing in across the longest dimension and with equal sized exit holes either in the roof of the canopy or as high up as possible in back close to the centerline of the tank so the air has to travel at least half way across before it exits works best. With one in and one out you waste the capacity of one fan since it only moves what the other fan sends it and does not contribute.
I have tried many many variations including one in and one out, up high, down low, high speed, low speed, 120v AC, 12v DC, DC variable voltage, mounted in the roof pointed down, mounted in the roof sucking out, more fans, bigger fans etc.
Another advantage of my method is it also takes advantage of natural convection. You can place your hand over the exit holesand even with the fans not running you can feel heat rising out the top. With both blowing in cooler, dryer air the fans last longer and do not gum up like fans pulling moist hot air out which fail much quicker. I had big multi page thread on a local AZ reef forum but it went under so I lost all my work. I went into great detail including photos of the canopy construction from the beginning, brands and models of fans and variable voltage power supplies and even temperature data before and after.
I also have the same Wal Mart clip on fan clipped on the edge of my sump as a back up. If my RKL controller sees a temperature rise it turns that fan on as a back up. This arrangement worked well over a 100G mixed reef with a 30G sump and 2x250w MH and 2x140w VHO actinics running 10 hrs a day in Phoenix AZ even in the summer months and with both of us away at work and a digital set back thermostat on the house AC set up to 80 during the day. The tank stayed between 79 and 81 easily in the summer and I had to slow the fans down in winter or it got too cold and turned the heaters on.
I have tried many many variations including one in and one out, up high, down low, high speed, low speed, 120v AC, 12v DC, DC variable voltage, mounted in the roof pointed down, mounted in the roof sucking out, more fans, bigger fans etc.
Another advantage of my method is it also takes advantage of natural convection. You can place your hand over the exit holesand even with the fans not running you can feel heat rising out the top. With both blowing in cooler, dryer air the fans last longer and do not gum up like fans pulling moist hot air out which fail much quicker. I had big multi page thread on a local AZ reef forum but it went under so I lost all my work. I went into great detail including photos of the canopy construction from the beginning, brands and models of fans and variable voltage power supplies and even temperature data before and after.
I also have the same Wal Mart clip on fan clipped on the edge of my sump as a back up. If my RKL controller sees a temperature rise it turns that fan on as a back up. This arrangement worked well over a 100G mixed reef with a 30G sump and 2x250w MH and 2x140w VHO actinics running 10 hrs a day in Phoenix AZ even in the summer months and with both of us away at work and a digital set back thermostat on the house AC set up to 80 during the day. The tank stayed between 79 and 81 easily in the summer and I had to slow the fans down in winter or it got too cold and turned the heaters on.
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I picked up X2 80mm 12v fans today I have fitted one to the side and put same size hole opposite at the other end and normally if I close the lid I will see .2-.3 rise within a hour but within 20min my temp dropped .2 and kicked the heater in 
have got it plugged into my stc1000 to control my heater and fan
have got it plugged into my stc1000 to control my heater and fan 
