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.
Steve
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.
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.
Dan
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.
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