Variable Speed Booster With the Coal-Trol

Variable Speed booster with the coal-trol

PostBy: tmbm50 On: Fri Nov 16, 2007 9:19 am

I'd like to place a booster fan to draw air from my LL stove and have it controlled by the coal-trol. I went to a local Heating/Cooling supply store and they told me that they did not carry any booster fans that would work becuase the coal-trol uses a variable speed fan. And that unless the fan is specifically made for variable speed it will burn out the motor.

Is that true?

They only duct fans that I can find that are variable speed have their own speed control mechanism. I was looking at these fans
**Broken Link(s) Removed** as recommend on another thread (I guess this use to be or something) but the other thread wasn't specific to the coal-trol.

What are you guys using with your coal-trol for a duct fan. It also look like the coal trol is limited to .6 amps which seems to limit the choices as well.

Re: Variable Speed booster with the coal-trol

PostBy: pvolcko On: Fri Nov 16, 2007 10:25 am

The convection fan output of the Coal-trol control module is rated at 3A. We will speed control any shaded-pole type motor. There are some motor types we do not work with, such as centrifigual switch or capacitor start motors, but it would be unusual for a duct fan to be a "problem" type. Also, fans being controlled by the Coal-trol can not have a rheostat inline between the Coal-trol and the fan, it will screw things up.

Assuming the duct fan in question is indeed a shaded-pole type and you are under the 3A limit for the output, the only other restriction with the Coal-trol is that you can not plug multiple motors/fan into the convection output unless all the motors are of the exact same type (same ratings, same size, i.e. a matched set of fans). So, if the duct fan is the only thing you intend to run off this output of the Coal-trol, no problem. If you are wanting to running multiple duct fans, make sure they are all matched (same size and ratings and brand/manufacturer) and the total current of the fans is below 3A, no problem. If you're wanting to run different duct fans or a mix of duct fans and normal stove mounted convection fan(s) then you will have a problem.

Re: Variable Speed booster with the coal-trol

PostBy: tmbm50 On: Mon Dec 03, 2007 11:17 am

Quick follow-up question. I asked the manufacture is their fan was a shaded pole and he said it was not but did say their fans can be speed controlled by simply adjusting the voltage up or down using a "using inexpensive solid state speed controls, transformers or VFDs"

Is the coal-trol simply adjusting the voltage?


Re: Variable Speed booster with the coal-trol

PostBy: pvolcko On: Mon Dec 03, 2007 7:41 pm

Not sure what just happened. I posted a reply and it doesn't seem to have shown up. :)

At the end of the day, without specific knowledge of what kind of fan it is, the best and only way to know is to buy one and try it. If it can be returned if you don't like it, then I'd suggest this route.

Our control does adjust the average power applied to the motor, but this is not always enough to achieve reliable speed control of some types of motors. Centrifugal switch motors, synchronous motors, and some others are motor types we can not reliably speed control. Shaded pole and split permanent capacitor motors (also called "capacitor run" motors) are controllable with the Coal-trol.