From: davenpete@gmail.com   
      
   Hi all,   
      
   We have been given two 2200cfm fans (Lakso 20" box) and am thinking of   
   mounting them in series and then fitting the assembly to the man-hole opening   
   into the ceiling crawl space. The idea is to use a timer to run them during   
   the night when it is cooler    
   outside suck air through the place. They are close to the same size as the   
   opening into the ceiling so series makes sense.   
      
   Does anyone have details on how far apart to mount them for the best   
   efficiency? I have been testing with a small 12v fan and voltmeter in front of   
   them and moving them closer or farther apart. It does not seem to make much   
   difference to the voltage    
   developed by the small wind-driven 12v fan on where they are placed.   
      
   With one fan, the voltage generated is pretty stable at 1.47vdc. With them in   
   series, it is around 1.98vdc and I can't seem to find any sweet spot.   
      
   I have found this graph, which shows almost double output for a large   
   percentage of the flow volume but I am not seeing that.   
      
   http://www.greenheck.com/images/articles/fansinseriesgraph.gif   
      
   Thoughts and helpful suggestions?   
      
   Thanks   
      
   Dave   
      
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