Hi Folks,
I’m looking at adding an extra 24v cooling fan as done here http://www.thingiverse.com/thing:716002/#collections Here it has been wired in parallel with the standard fan. Is this wise to do as i don’t want to draw excessive amps on the standard system and let the blue smoke escape ! my other thought is to swap out and use 2 12v fans
Most of the heavy current drain on the system is over by the time the print cooling fans are turned on. So it might be safe to have them in parallel. 
I run 2 24v cooling fans on mine. No smoke. Fixes the left facing overhang messiness I used to get.
Cheers guys, I’ll give it a go!
I’m going to be upgrading to a dual extruder soon and am thinking about this same issue, sort of. On my original extruder I replaced the small heat sink micro blower fan with a 40mm fan in order to stop heat creep, but the dual doesn’t really have space to do that, so I’m thinking of just adding a second micro blower to each extruder. I figure the best way to connect the new fans is to wire them in parallel with the stock fans, but I’m no electronics guru, so I’m wondering A) will that create any hazards, and B) is there a more simple way to add two more fans?
If you put a fan on the left side of the extruder, you have to be careful not to run into anything when you zero the X-axis. Often, you must put on new stop of the X-axis limit switch to keep the fan from running into the printer frame, etc.
I “mirror” printed a regular right-hand fan and mounted it on the left-hand side. I then attached a small blade to trigger the limit switch ~0.5 inch further out.
The few extra mA draw of an additional 40mm fan is tiny compared to the big amps that the heater draws. They also have two fans on the dual extruder as well as the new Taz6. The fans are simply wired in parallel.
You will really like the nice prints you get with even cooling from two fans. I have two fans on my flexistruder.
Bill D.