Adding A Fourth, Lower Speed To Fan - HVAC - DIY Chatroom Home Improvement Forum

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Old 05-27-2012, 02:19 PM   #1
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Adding a Fourth, Lower Speed to Fan

My window-mounted, evaporative cooler has a three speed, permanent
split capacitor (PSC) motor. A guy at a Home Depot review site for this cooler said he "added a fourth speed--1/3 of the lowest speed." He did not explain, and there is no email address to write him. Can anyone say how to do this?

Alternatively, what do people think of the following solution, using a dimmer?

Set the switch to "High." Disconnect wires from the low and medium speed terminals.

Cut the lead supplying power to the motor.

Add variable control in series. Use one of the dimmers that is variable from electrical supply stores. The dimmer must be a "triac" and not an "SCR." SCR's work great with resistive loads but not with inductive unless certain conditions are met.

Speed may now be varied down to about 20% of the motor's rated speed.


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