Automatic Thermal Overloads

[lanier]

I am looking for information on Automatic Thermal Overloads (ATO), specifically on installation. What is the best location and how do they actually work? I have looked at websites for manufacturers and cannot find any detailed information. Any information is welcome, links to websites are welcome as well.

 

[wbd]

Are you asking about automatic resetting of a thermal overload for motors? I have seen some starters that have a thermal overload that can be set to auto reset.
I have never used that feature - have always had the overloads be reset manually. I have done that since if the motor tripped out on OL, there's usually a reason. By keeping the reset a manual action, someone has to physically go there, look at motor (smell, feel, observe), reset OL's, restart motor. If not further tripping of OL - fine. If trips again - get electrician and take amp readings, compare with nameplate, etc.

 

[lanier]

I am talking about the ATO's that are used inside the motor itself, not in a starter.

 

[PUMPDESIGNER]

On small single phase induction motors up to 2 hp there is often a thermal switch inside the motor, usually at the back where the connections are made. Internal heat causes the switch to open, and when internal heat dissipates the switch resets itself. The device used is often called a snap disc because it is a small round concave bi-metallic disc that inverts itself suddenly causing an audible "snap".

If this is what you are interested in just do a search on Google for snap switch.

Above 2 hp I only know of sensors used in large submersible sump and sewage pumps. I know little about that application. Richard Neff
Irrigation Craft