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Old 01-27-2017, 11:06 AM   #1
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1979 31' Excella 500
Charlevoix , Michigan
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Fan Speed Controller for inline HVAC booster

I have 2 blower fans (normally used to vent engine compartments on boats of fumes before starting engine) installed as inline HVAC airflow boosters. I know, I know... for all the HVAC people out there they will notice right away that this is a poor method of trying to boost airflow. Needless to say, my options were limited at the time and this was the best available method to increase airflow from the furnace to colder areas of our AS.

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I currently have a voltage regulator installed on each of these fans to allow for some control over the speed of each fan:

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Unfortunately, they aren't rated to handle more than 3A and one of them has already failed due to the draw of the fan it's attached to. I am looking for a replacement.

I was wondering if anyone could recommend a voltage regulator or fan speed controller on that would service this purpose. Wondering if this one would suffice:

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Name:	2017-01-27 13_02_03-Amazon.com_ Yeeco 9-60V PWM DC Motor Speed Controller Pulse Width Modulation.jpg
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Old 01-27-2017, 11:57 PM   #2
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I don't know how much current your in-line fans draw, but a 20A speed control should certainly be more than capable of handling the job. In your picture they look similar to computer "muffin" fan motors, and those typically draw less than an amp at full speed.

Just a note -- a PWM speed controller does not work by regulating voltage. PWM stands for "Pulse Width Modulation" the motor is always being supplied with the full 12 volts, but the feed is electronically pulsed. The longer the width of those pulses, the closer to full speed -- the shorter -- the slower. They are far superior to the old variable resistance controllers because they to not used wasteful resistance to control voltage.


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Old 01-28-2017, 06:41 AM   #3
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The electronics crapped out on one of our expensive MaxxAir fans. I fixed it in 20 minutes with one of these. Cheap and works awesome.
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Old 01-28-2017, 07:44 AM   #4
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Oswego , Illinois
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Here is my answer to the same problem:

Post #29 has a link to a good , electrically quiet, PWM controller. A Bit pricey, but I had to buy 2 or 3 different ones until I understood what it took for the noise to stop.

This part of the project was to provide more heat to the tanks. Another old thread covered duct additions and changes to provide more heat to the bedroom.

"If the women don't find you handsome, they should at least find you handy." - Red Green
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Old 02-01-2017, 09:28 AM   #5
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1979 31' Excella 500
Charlevoix , Michigan
Join Date: Aug 2014
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Thanks for the replies everyone!

So... can you use a PWM controller with ANY type of fan? Or does the fan have to support PWM?

Reason I ask is because the fans I have only have a positive and a negative wire coming from them. There's no 3rd wire like you'd see on a computer case fan or something that allows speed control...
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Old 02-02-2017, 10:45 AM   #6
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1979 31' Excella 500
Charlevoix , Michigan
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Posts: 299
For those following this thread, I went with this fan speed controller (really just an adjustable voltage regulator):

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Name:	2017-02-02 12_43_05-Amazon.com_ DROK Numerical Control Voltage Regulator DC 6-40V to 0-32V 5A Bu.jpg
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My last one burned out, but this one has heatsinks, so hoping that will make 'em last a little longer. Was hoping just for an analog thumb dial version, but couldn't find one of those for a reasonable price. We'll see how these turn out!
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Old 02-14-2017, 10:17 AM   #7
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1979 31' Excella 500
Charlevoix , Michigan
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It works!

Added the voltage controller noted above and the setup works nicely. The unit itself is pretty over-kill for my application (would have just preferred a simple thumb-dial) but it works exactly how I needed it to.

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