evilknieval69 Posted December 7, 2006 Report Share Posted December 7, 2006 Ok, well i have figured out a good way of attaching the reflector and bulbs etc to the top of the hood, and the bottom of the bulb sits about 5 cm down from the top so im going to aim at having 25cm in between the bottom of the bulb and the top of water, making it about 20cm to the bottom of the reflector.... I do think it will be sweet for a 38cm high tank.... I will take pics and stuf when i get round to making it (got to get the tank first) Quote Link to comment Share on other sites More sharing options...
Ira Posted December 7, 2006 Report Share Posted December 7, 2006 Keep in mind if you have the fans sucking air out of the hood you'll have heaps of nice moist salty air doing its best to eat your fans. Quote Link to comment Share on other sites More sharing options...
wasp Posted December 7, 2006 Report Share Posted December 7, 2006 Should fans suck or blow? Imagine you are eating dinner, and the potato on your fork is too hot to put in your mouth. To cool it, would you blow air on it, or, suck air off it? Quote Link to comment Share on other sites More sharing options...
Ira Posted December 7, 2006 Report Share Posted December 7, 2006 It depends. Are you feeling cold or hot? If you want to direct the air at the water's surface blowing would be best. If you're trying to vent the air to a specific place(Like out a window or something) then it would probably be best to have them sucking. The total volume of airflow is going to be similar either way. Quote Link to comment Share on other sites More sharing options...
cookie extreme Posted December 7, 2006 Report Share Posted December 7, 2006 Should fans suck or blow bit of a rude question isn't it? let them do which ever they like!! Quote Link to comment Share on other sites More sharing options...
Zev Posted December 7, 2006 Report Share Posted December 7, 2006 bit of a rude question isn't it? let them do which ever they like!! Lol! It's all about polarity! Quote Link to comment Share on other sites More sharing options...
steve-s Posted December 7, 2006 Author Report Share Posted December 7, 2006 In the mounting of 2 fans I plan on cutting holes in the side of the hood and mounting the fans flush in those holes so that the fan sits just below the halide. I have a few options: 1. Both fans running in the same direction, one blowing air into the hood and the other removing it from the other side. 2. Both fans running in opposite directions, both extracting air from the hood, airflow in would then come from the open back. 3. Both fans running in opposite directions, both blowing air into the hood, airflow out would then go through the open back. Which would be the most effective? Is Ira right, will the salt water erode the fan if it is extracting, how quickly can this happen? If so should I have both fans blowing inward (option3)? Option 1 seems logical to me but as the tank/hood is only 45cm wide it's quite possible that the cool air brought in by the first fan would be propelled across the hood and most of it would go straight back out the other fan which would be extracting. If this did happen then very little hot air would get removed. Anyone got any thoughts? Cheers, Steve Quote Link to comment Share on other sites More sharing options...
wasp Posted December 7, 2006 Report Share Posted December 7, 2006 There would be little point having one blowing in, and one out, because where the one blowing out is, you could simply have a hole, and the other one blowing in would cause the air to be expelled anyway. I use fans for cooling and found it most effective when the fan is pointing at the water at a bit of an angle, blasting strongly enough to cause reasonable disturbance to the water surface. I've actually done tests on this, albeit not very scientific, but am certain that blowing onto the water surface fairly hard is most effective at cooling. So, if it were me, I'd have both fans blowing inwards, at such an angle as to cause disturbance at the water surface. Allow some means for this air to be able to exit the hood reasonably unimpeded also. Another thing, this can cause quite an increase in evaporation, need to consider that with whatever your top off system is. But this is nessecary to get the full amount of cooling. For venting, you may or may not wish to vent air in, out, or both. My fans are on a temperature controller, in order to attempt to imitate nature and get a gentle rise in temperature during the day, rather than a series of ups and downs, there is one fan comes on first, and this is followed by another if the temperature goes up another degree F. Then another degree F higher the chiller comes on which drops it back to the cut off point of the second fan. Quote Link to comment Share on other sites More sharing options...
suphew Posted December 8, 2006 Report Share Posted December 8, 2006 Is Ira right, will the salt water erode the fan if it is extracting, how quickly can this happen? I have a proper extracter fan (all be it a cheap one) removing the air from my enclosed hood and pumping it outside. The fan itself is 3 or so meters away from the tank down some 6inch pipe, I have had to replace the fan, it lasted about 9 months. This time round I removed the wire joiner block and soldered then sealed the wires, covered the fan motor with CRC and put some filter wool over the intake. Was only replace a month or two ago so don't know if this is going to make it last any longer. Quote Link to comment Share on other sites More sharing options...
steve-s Posted December 8, 2006 Author Report Share Posted December 8, 2006 My fans are on a temperature controller, in order to attempt to imitate nature and get a gentle rise in temperature during the day, rather than a series of ups and downs, there is one fan comes on first, and this is followed by another if the temperature goes up another degree F. Then another degree F higher the chiller comes on which drops it back to the cut off point of the second fan. Sounds brilliant, what do you use for a temp controller or where do you get them? I was going to run the fans on the same timer as the lights but to be able to base it on the water temp would be perfect. I have a proper extracter fan (all be it a cheap one) removing the air from my enclosed hood and pumping it outside. The fan itself is 3 or so meters away from the tank down some 6inch pipe, I have had to replace the fan, it lasted about 9 months. This time round I removed the wire joiner block and soldered then sealed the wires, covered the fan motor with CRC and put some filter wool over the intake. Was only replace a month or two ago so don't know if this is going to make it last any longer. Hopefully you can get a few more months out of it, 9 months isnt too bad, these PC fans cost $13 each, even if both had to be replaced, I'd spend much more than that on a new halide globe each year. I picked up the fans today along with a 12v DC transformer. Todays lesson was - Dont stand up your PC fans on the bench and then plug them in, the rush of air generated may cause the fan to whiz across the bench and shatter a couple of fan blades. :oops: Luckily I could glue them back on and the fan seems to work fine. I will mount them tommorow, I think I will go with them both blowing as I think the general concensus seems to be that blowing on the surface will cool slightly better and sucking will bugger the fan. Oh, hopefully I'll get around to adding some pics over the weekend. Cheers, Steve Quote Link to comment Share on other sites More sharing options...
wasp Posted December 8, 2006 Report Share Posted December 8, 2006 Sounds brilliant, what do you use for a temp controller or where do you get them? I was going to run the fans on the same timer as the lights but to be able to base it on the water temp would be perfect.Steve Mine is an Aqua Logic Nema 4x, I used to run the fans on a timer as you are thinking of doing, and that is certainly a good cheap option. The controller just makes things a bit better and also gives me comfort that things will not overheat on those occasional very hot nights we get when the timer would not have had the fans on. There are a couple of guys selling temperature controllers in the For Sale section, plus there are some more guys on the forum, who may wish to chip in, who can supply or make them. http://www.fnzas.org.nz/fishroom/digita ... 16716.html http://www.fnzas.org.nz/fishroom/digita ... 16736.html Quote Link to comment Share on other sites More sharing options...
shaneo Posted December 9, 2006 Report Share Posted December 9, 2006 I use fans for cooling and found it most effective when the fan is pointing at the water at a bit of an angle, blasting strongly enough to cause reasonable disturbance to the water surface. I've actually done tests on this, albeit not very scientific, but am certain that blowing onto the water surface fairly hard is most effective at cooling. That is exactly what I have. One 100mm fan on a 45 deg angle that creates surface disturbance, switched on and off by a Nema 4x temp controller. My temp only shifts by 1 deg a day 8) Quote Link to comment Share on other sites More sharing options...
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