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I have a (high velocity air) dual AC brush motor pet hair dryer (details). (There is no heating element.) It's rated at 120 Volts 18.5 Amps. It has a rotary knob (listed on the parts page as a "Variable Speed Switch and Circuit Board") that clicks on & off and then rotates to set the motors' speed. It's a bit of a pain to click it on and then find the desired speed setting each time. Plus it's wall mounted and a bit hard to reach. I'd like to plug it into a switched wall outlet and use that to turn it on and off, and leave the speed setting at the typical use level (about 90%). It that safe to do? Or can doing that cause damage to the motors or electronics?

[edit/update] It's currently on a 20 amp circuit and I would have an electrician install a properly rated wall switch for this.

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Universal motors are often started and stopped with a switch and not speed controlled at all. It seems unlikely that the speed controller or motor would be damaged by switching it on and off. However the linked web page contains the statement "If you need knowledgeable advice about your product we urge you to call." Starting is stressful for any motor and starting many times every day may shorten the life of the product. There is no way to tell by looking at the sales information is the speed control does anything to reduce starting stress. My guess would be that is doesn't.

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If the unit really uses 18.5 Amp, it cannot be used on a normal 15 Amp circuit - it would need a 20 Amp or higher rated circuit, and and would require a heavy-duty switch or contactor rated for that current or motor horsepower. A normal light switch would not handle that current.

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  • \$\begingroup\$ Thank you for the response. I edited my question to note that it's currently on a 20 amp circuit and I would have an electrician install a properly rated wall switch for this. Thanks for pointing that out. So with that in mind, using an "external" switch to cut/supply power to turn it off & on would not be damaging to the unit? \$\endgroup\$ – Lance Miller Jul 20 '19 at 17:54

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