Does your canopy suck or blow?

[btacker]

I was wondering if ya'll could share how air flows through your canopy with Metal Halides.

Right now, my canopy only has 2 IceCap 4 inch Variable Output fans that suck air into the canopy. There is no lower back on the conopy, but there is an upper back.

Should these side fans continue to suck air in or should they blow air out?

I was thinking about putting a hole in the top for a fan to blow air out. Sound like a good idea?

Right now, I have our AC set on 78 and with the MH on, my tank runs around 82.

[jaded]

In my opinion you are set up correctly now. I prefer to suck air into the canopy and have ample room for exhaust to escape out the back (past the hot stuff). This will help to keep your fans free of salt buildup and moisture as well as do a good job of moving air over the water to help with evaporative cooling.

[z28pwr]

When I put fans I have one pushing air into the canopy and one pulling air out of the canopy, thus creating a flow of air through the canopy.

[brewercm]

I always leave my canopies backs open when I build them so my fans strictly push air in.

[::pete::]

Its best to blow the cool air across the water after all thats why the fans are installed ... cooling by evaporation. If the fans are pulling from the canopy you are just taking the heat from the canopy out and not actually cooling the water by evaporation. Also with the salt creep and such it will shorten the life of your fan with the moist air always coming across the fan.

[Dozer]

I'm doing what Brewer and pete are. Canopy back open, two clip on fans are behind pointing at the halide pendants and the water surface. It's working really well for me. Makes about a 5 degree difference- 80 degrees vs. 85+ in my case.

[Polkster13]

My canopy "sucks" and "blows" and it doesn't even have fans! :lol

[eric]

Just a hole in the top (without even another fan) might be the trick you're looking for. Just to allow hot (moist) air an easier escape.

Get a fan close enough to splashing or bubble pops, you're gonna get the salt creep no matter what you do. Trying to blow or suck air "out" is going to draw the humid air through the fan and just shorten it's life. It's not that moist of air though - salt creep will kill the fan much quicker if not cleaned.

The more dry air you can get in contact with the water surface, the more evaporation you'll get. Heat want's to transfer to the cooler fluid (air in this case). The temp and moisture content of that air determines how much more evaporated water (and with it the heat rejection) that air can hold.

I think the best setup would have 1) one or more fans drawing air "in" to the canopy in a way to draw the most outside air volume across the surface and 2) a vent in the top to allow the warmer air easiest escape.

If the vent/exit is not at the highest point (top or top section of one side), you're trapping hot air rising. You can create enough air flow to counter this, but in my opinion why waste the fan effort when the qualities of hot air will do it for free.

[::pete::]

Like this ... http://offthereef.org/images/sa%20canopy%201.jpg

[Polkster13]

Very sweet Pete! I know who I am calling the next time I need a hood or stand.

Sorry I haven't gotten back to you yet on the skimmer. Has been a mad house around my place. Still debating on whether or not I should go internal or external. You going to be up my way anytime in the next couple of weeks?

[eric]

That there is pretty. Oak, I believe? And I must say meets all of my personal criteria. Are you putting a mechanism of sort to hold the front up when opening?

[::pete::]

Yea the top or the rest of the canopy