Question about electric fan
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
A relay-controlled fan means the fan is either on or off; if it's off, the fan does not spin; if it's on, the fan spins at full speed. A PWM-controlled fan means the exact speed of the fan can be adjusted within some range.
PWM fan controllers are expensive and there is no point to have one for this application, in my opinion. With a relay-controlled setup, you should already be using a temperature switch to cut off the relay under a certain temperature. That is already one form of modulation. With the simple relay setup, the fan will be off below a certain temperature, and it will be on all the time past a certain temperature. There is limited quantitative gain in dynamically adjusting the speed of the fan once it's on with a PWM controller. I don't see the point when in reality you don't care that your coolant temperature fluctuates within a few degrees.
PWM fan controllers are expensive and there is no point to have one for this application, in my opinion. With a relay-controlled setup, you should already be using a temperature switch to cut off the relay under a certain temperature. That is already one form of modulation. With the simple relay setup, the fan will be off below a certain temperature, and it will be on all the time past a certain temperature. There is limited quantitative gain in dynamically adjusting the speed of the fan once it's on with a PWM controller. I don't see the point when in reality you don't care that your coolant temperature fluctuates within a few degrees.
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