Completed Project Which among these two fans are better for cooling? Also can a shaded pole fan be controlled via dimmer?

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Joined Dec 16, 2016

I'm building a DIY lab round flask heater using a fiber glass 250mL GLAS-COL M102, 180 Watts heater mantle. The temperature will be controlled via a PID controller and a K-type thermocouple. Since the metal outer shield of the heater also gets hot during the operation and the PID controller will also be placed inside the housing I need to remove the heat from the inside. I have two types of axial cooling fans in my possession (picture shown in attachment). Now, the No. 1 type fan is quite powerful, noisy and the air has a lot of force to it. But you can feel the air flow pressure only unto 2-3 ft from the fan. The No.2 fan though not very loud or powerful, the air flow can be felt even up to 5-6ft away though the force from the air is not quite high like the former. I want to use a 115VAC fan to avoid using another circuit if I were to go with a 12VDC fan.

I'm assuming these are shaded pole motor fans. Can the speed of these fans be controlled via a simple light dimmer or the need a specific motor speed controller (maybe a triac controller)? Also if I used a light dimmer and wanted a slower speed to reduce noise, will the motor stall after a certain point and cause it to overheat?



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Joined Jul 18, 2013
They are most likley shaded pole, they can be controlled by Triac 'Dimmer' style usually.
But shaded pole motors do run hot and usually have to be turned high or full on to start.
Then the RPM can be lowered.
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Joined Dec 2, 2017
No 1 Fan has a wider dispersal flow.
No 2 Fan has a more narrow dispersal.

No 1 would probably provide more cooling in an enclosure.

Triac lamp dimmers could work but some don’t have the suppression needed to run motors.


Joined Sep 7, 2010
The fan with five blades is designed for fast flow against low back pressure ....

The other fan slower flow but can deal with higher back pressure ...

So it depends what resistance the path of flow offers , pushing air through a cramped enclosure with many obstacles will tend to stall flow from the 5 bladed fan more .... the other fan will push the air through ....

But when there is little resistance to air flow , the 5 bladed is more efficient .

You can tell by looking through the fan blades ... if you can see through then it's fast flow , low pressure ...If the blades prevent you seeing through , fill all the space , then it's higher pressure lower flow.
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