How much heat to expect with (2) 175w mh??

[johnnysalt]

I'm putting them into a hood that is closed on the back....but I'll add three fans....I'm thinking two on the back (close to the bottom of the hood) blowing in and one on the top pulling air out. Either that or three blowing in. The bulbs will be about 7-8" above the surface of the water. Because I don't have 12" in height I think I'm gonna choose 175w over 250. Tank is 100g...sump is 30g. Only other lighting is two NO bulbs.
For those of you that have something comparable to that, did you need all the fans? What chance do I have with keeping the temp reasonable if I had the 3 fans going?
Also....evap rate now is 1/2gal/day....what can I expect it will raise to after the new lights/fans?
Thanks for your help in advance!
John

 

[jester]

I've got 3 175's in an enclosed hood I only use 1 4" fan sucking air out and a 4" filtered hole on the otherside. My lights are only 2-3" above water, but shielded by 1/4 plexi. I evap 2-3 gallons a day, the tank temp is usually 76-78 without a heater. the lights are only on for about 4-6 hours a day.
Recomendation: Pull the hot air out. If you force cool air in, it is not as effective as the air just swirls around inside.

 

[marinemarty]

Hi, I have dual 175 and dual 95 VHO actinics, I have the lights enclosed in a hood with a 5 inch fan on either end. i sucks in and the other pulls air out. I currently have them sitting on top of my glass tops. The hood also has a plexiglass shield. My temp has stabalized at 83 and change. I have a 75 gallon with a 16 gallon sump and 22 gallon refuge. HTH
Martin

 

[slick]

I have 2 175w mh's and 260w of pc's on my 90. My cannopy is open on the back and I only (currently) run a small 2 inch fan pulling hot air out the top. My temp is 80. My lights are 8 inches off the surface with no glass tops. Not sure on evap but it's more that a gallon. Put all 3 fans in the top blowing up toward the celing.