View Full Version : controlling temp with a fan only - does this sound like an ok thing to do

10/11/2005, 09:50 AM
I was wondering if anyone has any thoughts about this method for controlling the temp in my tank. Nothing revolutionary here - just thought it would be good to get a few other thoughts on the matter.

Currently the tank stays a bit on the high side (80-82), but fluctuates a bit more than I like, due to equipment heat. I dont have a chiller The heaters are set around 78-79 - I really dont think they even come on at all. So my high temp is primarily due to the equipment I have (internal return pumps and skimmers, powerheads, MH lights, etc).

So if I wanted to control the temp with the heater, I would need to set it towards the high side, around 82.5, to consistently stay above the temp created by my fluctuating equipment heat. Seems like a better idea to me to have the temp controlled by a clip-on fan over the sump. That way, I can have the fan come on any time the tank gets above 80, and when it gets lower, have the tanks normal operating equipment bring it back up to ~80.

So the commands would be like this:
If Temp > 80.0, Then FAN On
If Temp < 79.5, Then FAN Off
If Temp < 79.0, Then HTR On
If Temp > 79.5, Then HTR Off

Does this all make sense? In this scenario, the heaters still probably wont come on normally (an idea I like, due to the extra power consumtions required by heaters). But they will be set to come on as a back up, in case the temp were to fall too low, say at 79 or so (a temp I rarely see my tank get to). I also like the fact that this will force the fan over the sump to come on pretty often - the fan uses much less power to operate than a heater, and it will force additional evaporation so I can top-off more kalk (another thing I had been hoping to do).

What do you think of this? One thing I was wondering was if the fan would have too much troubling battling the heat generated by the tank equipment, then it might wind up running continuously all day long. I guess I might have to tweak temps a bit to find the right spot.

10/11/2005, 10:58 AM
I see nothing wrong with 82 temp. That is about the low temp on my tank.

10/11/2005, 11:09 AM
Maybe 82 is ok, although it might be on the edge (i should maybe mention that in the heat of summer I have seen 83 and even 84 - thats when I get nervous).

But my choice is to either control it on the high side with a 250w power hungry heater. Or control it on the lower side with a 35w fan, and let the tanks normal operating equipment supply the heating power for me.

Or I suppose I could control it with nothing (which is really what I have been doing currently with my heater not even coming on), and letting the temp just fluctuate up and down with the equipment heat between 80 - 82, occasional spikes to 83, etc.

10/11/2005, 11:31 AM
I use 2 computor fans in my canopy blowing across water. It drops the temp a good 4 degrees.

10/11/2005, 04:23 PM
For those extra hot days you can always float a 2 litre bottle of frozen water in your sump, that is what we did until we invested in a chiller.

Right now our temp set up is such that we have 2 heaters, with overlapping temps, fans and a chiller, with a median temperature of 80. So far it has worked out great for us... :)