Thanks, everyone for all the input. To answer several questions and comments at once:
The fans are mounted directly to the top of the controller which is essentially a sealed metal box. The top looks to be an extruded aluminum case with mild fins (1/8" deep). The fans are not intended for wet use, but I don't think they will get wet on top of the controller under the hood. I am more worried about dust from my gravel driveway; it gets everywhere. I am going to see how well they last. These are meant to be computer case fans, so this usage is outside their design, but they were cheap. For now, I will probably leave the fans blowing away from the controller. As much because they are already that way, as anything. I will measure how hot the controller is above ambient after my commute home in the evening. If I ever reverse the fans, I will measure again. Mike > -----Original Message----- > From: [email protected] [mailto:[email protected]] On > Behalf Of Lee Hart > Sent: Monday, July 08, 2013 5:38 PM > To: Electric Vehicle Discussion List > Subject: Re: [EVDL] Fans Up or Down? > > Mike Scott wrote: > > Is the possible entry of water a problem? I've always though that the > > gap between the impeller and the frame should be on the bottom so that > > water could not fill the airspace in the fan motor. > > If the mounting location is such that it may get wet, then you really should be > using a fan with fully enclosed motor -- not one intended for dry indoor use. > Especially on a fan, water is going to get into *everything*, no matter how > you mount it. > > Dach Savage <[email protected]> wrote: > >> In most any ventilation or cooling scheme it is best to use the fan > >> in an exhaust mode, IE pulling the air out of a cabinet. > > You really have to look at the blade design. The manufacturers have > performance curves, showing air flow versus air pressure. Propeller fans are > very sensitive to air pressure, and the pressure difference between inlet and > outlet. Some blade designs will have a drastic reduction in airflow with even a > slight restriction or reduced air pressure at their inlet. Others can tolerate it > much better. > > The fans I've happened to use in product designs have generally worked > better by pressurize the cabinet. It extracts a bit more heat (the things being > cooled run a bit cooler), and it makes sure that any air leaks will let air out, > rather than suck in air (or dirt or water or bugs etc.) from uncontrolled cracks > or openings. > > -- > The greatest pleasure in life is to create something that wasn't there > before. -- Roy Spence > -- > Lee A. Hart, http://www.sunrise-ev.com/LeesEVs.htm > _______________________________________________ > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > For EV drag racing discussion, please use NEDRA > (http://groups.yahoo.com/group/NEDRA) _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
