Fan Modifications
Printed From: R-pod Owners Forum
Category: R-pod Discussion Forums
Forum Name: Podmods, Maintenance, Tips and Tricks
Forum Discription: Ask maintenance questions, share your podmods (modifications) and helpful tips
URL: http://www.rpod-owners.com/forum_posts.asp?TID=5408
Printed Date: 18 May 2024 at 2:52am
Software Version: Web Wiz Forums 9.64 - http://www.webwizforums.com
Topic: Fan Modifications
Posted By: Guests
Subject: Fan Modifications
Date Posted: 10 Oct 2014 at 3:08pm
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In another thread, there was some interest in modifying the interior fan in a non-Pod camper and a Fantastic Fan (like in the Pod). Having a Coleman TT, I replaced the OEM noisy/ineffective fan and modified it to run slower by installing a 10 watt/10 ohm resistor.
The two ideas in question are (I think): 1. Ways to slow down the Heng's Vortex single speed fan 2. Ways to further slow down the 3 speed Fantastic Fan (like the Pod's) One question asked was about potential heat (from the modification). Yes, heat is a concern when choosing a resistor and possibly heat build up in the motor when running a slow speed. The 10 watt resistor that I used is overkill but, it's what I had on hand. I can't foresee a situation where it would ever get hot. My Vortex runs roughly about the same as the Fantastic Fan on "medium" speed setting. Being oversized and with still plenty of air flow, it all stays cool. So, all electrical gurus out there, see pages 5 and 6 of Techntrek's new camper thread for further info. Let's see if we can solve the 2 questions above. Some issues that come to my mind are: amp draw at start up amp draw at running speed resistor size/value/fixed/variable VS relative RPM of the fan motor at what point does it not provide enough current to start the motor efficiency - amp draw VS motor speed Speed - I can only give a subjective account on my Vortex and that is: It seems to operate at about 75-80% of the manufacturer's speed. Any thoughts folks? PS - The person with the best ideas will win a free membership in this forum for all of 2015! |
Replies:
Posted By: techntrek
Date Posted: 10 Oct 2014 at 3:45pm
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Easy to figure out for something like LEDs, where you know the input voltage and the amperage of the LED, and need to meet the voltage of the LED's diode. A bit harder here w/o some real-world observations. Each fan model will need different resistors, although I expect they wouldn't be too different for the larger fans since they are about the same size. And the goal here is a different RPM, not a set voltage - which will be subjective, thus the need for observations. Resistor value X may be perfect as a "low" setting for brand Y, but be closer to "medium" for brand Z. Since your 10 ohm resistor is roughly "medium" for your fan, I'd say the first thing to try is a potentiometer that has an off setting and runs from 0 to maybe 30 ohms. ------------- Doug ~ '10 171 (2009-2015) ~ 2008 Salem ~ http://www.rpod-owners.com/forum_posts.asp?TID=1723 - Pod instruction manual 
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Posted By: furpod
Date Posted: 10 Oct 2014 at 7:08pm
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Why not just use a pot? and then I read the rest of Doug's post.. ------------- |
Posted By: CharlieM
Date Posted: 10 Oct 2014 at 9:16pm
As an EE with two degrees and 45+ years of engineering experience I can safely say "There ain't no simple answer". The speed vs voltage curve of a DC motor is not linear and the current vs voltage isn't either. So Doug's answer of using a pot to determine required resistance is the best we have unless someone with the exact same fan runs the experiment and publishes the results. Even then one person's definition of right is not the same as another person's. The best way would be to try a pot as Doug suggests, measure the current through the resistor, and install a pot rated to carry at least twice the measured current. Note I didn't say a pot with a certain rated power dissipation. Most pots are rated in power dissipation, but that's only when the entire pot is used. The rated current for a pot can be calculated from I=SQRT(Pd/R) where Pd is the rated power dissipation of the pot and R is the total resistance of the pot. The pot should be wired a variable resistor (rheostat), not a true potentiometer. OK! Enough geek talk. Write if you want more.  ------------- Charlie Northern Colorado OLD: 2013 RP-172, 2010 Honda Pilot 3.5L 4WD PRESENT: 2014 Camplite 21RBS, 2013 Supercharged Tacoma 4L V6 4WD |