New Hood

[Flatfish]

Looks like I gotta re-do the hood on my system. After struggling with the heat from the 2-400W Iwasaki bulbs I have concluded that I will never get enough airflow through the hood to keep it from raising the tank temp above 80. So it's back to the drawing board. The current hood is a standard design that you see over-and over. The system is in a corner so there is little airflow on two sides.
My thinking is that I need more distance between the bulbs and the water surface and give the heat a chance to rise out of the hood before radiating to the water surface.
The current setup with just VHO (two 48” tubes) sits at about 78.9-79 degrees with assistance from the heater. Room temperature is about 70 degrees day time, 65 at night. During peak summer the room temp can get in this high 70s for short periods. So I need to do something soon. The Iwasakis (at 9” from water surface) will raise the tank temp to 84 after 6 hours of operation which is totally unsat. The current hood is five sided with four fans, and vent holes in the top. Two 65cfm fans pull ambient air in from the rear.
The new design needs to be as ventilated as possible, while still being ascetically pleasing. I have thought about a pendant, but the light leakage will likely be too much since tank bottom is at 36” inches putting the pendant bottom at near 70”. The new hood will need to be tall enough to take the bulbs 12 to 14” off water surface (maybe more). So here’s what I’m thinking of doing:
A three sided enclosure with no back or top. A top cross member running length will support an internally hung adjustable pendant. The pendant will be constructed to house the entire lighting system (the two 400W Iwasakis and two 48” VHO tubes). Fans will be oriented to get as much ambient air into the hood as possible. The orientation of these fans has not been figured out yet.
Has anyone built of seen a hood like this? Do you think more distans and airflow will cut it? The alternative to the new hood is a downgrade of the 400W to 250W.

[Geoff]

on my hood, which has 2-400w iwasakis and 2 6' VHO's, i have 5-3" fans on the back blowing in, and 3 4" fans on the top. 2 are blowing out and the one in the middle is blowing in. this seems to work well. it is hard for me to tell because i added a chiller a month ago. but i can tell that it keeps the temp. in the hood to the low 90's. before the 3 larger fans on top it would creep up near 100, even overdriving the rear fans. it takes a lot of fans to keep those 400watters cool.

the larger the fans the better. see if you could fit a 6" or 8" fan or two in the new hood.

HTH,

G~

[grazhopr]

I have thought of a chimney looking canopy. It's odd looking but it should work pretty well.
A cone shaped or tapered top with an extractor would do the trick.
The taper should accelerate the hot air being pulled by a really big fan. it would work similar to those stove canopies to extract greasy air. If I rebuilt my canopy at this moment, I'd try something like it...

[NewReefer]

let me get this straight, your tank temp. is 90's? WoW and i its doing great? What all do you have living in there? I'm just curious because most people say 78 is ideal, I have a hard time keeping my tank at 80.5 with just 3 60" VHO's!

Originally posted by Geoff
on my hood, which has 2-400w iwasakis and 2 6' VHO's, the low 90's. before the 3 larger fans on top it would creep up near 100,
G~

[thefatman]

no no no.. his air temp between water and lights is 90

then that heats the water. but there is a lot of water.. soooo it will cause is tank to be about 84

[NewReefer]

OOps, reread it! Still 84 is hot.

[Geoff]

thanks jay, yes the air temp in the hood is 90.

84 is a little warm for a tank temp. unless you are doing a tidal pool aquarium?

now there is an idea. no need to worry about chillers there. water temp can get up in the 90's in some pools. of course not a whole lot lives in the pools, but still if you live near one, a neat idea.

G~