Dimmer on an electric motor?

I want to put a low rpm motor on a pump to aid a thermosiphon device. It's for an outside shower, and I think the thermosiphon would just move too slowly. I found a pump, but it needs a drive. Would I be better off to just buy a low RPM motor, even a 12v. DC and run it off a transformer, or would an AC motor work with a dimmer without damage? The resistance on shaft drag would be minimal, so a small 12v. DC should handle it.

Hint: I got a couple of 1.3 and 1/4 hp motors laying around.


Reply to
Loading thread data ...

only universal (AC/DC) motors are amendable to speed control via a dimmer, and then only if the dimmer can handle the back emf from the motor.

Reply to
William Noble

Try thrift stores and look for a weed wacker. The ones I have looked at use a PM motor. They turn fast for your application, but can be run at lower speed with a dimmer. You might also find a exercise treadmill and use the motor from it. Single phase induction motors will not work.


Reply to

Buy the motor you need for the job you want to do - a Shurflo 12V RV water pump would fit for this - and be done.

You can't use a standard light dimmer on a standard AC induction motor - they do make fan speed controls that will handle the EMF from the motor, but they're usually for smaller fractional HP motors like exhaust fans and ceiling fans. Even 1/4 HP may be too much.

If you want to use a regular pump, you can always rig a bypass relief valve to lower the output. Don't just throttle it with a valve on the suction or output, then it cavitates and chews up the impeller. Or make it a belt drive, and put a speed reduction in the pulleys.


Reply to
Bruce L. Bergman

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.