ITE Goulds motor starter question

[Lisagrantb]

I was given this starter and now I'm trying to figure out the wiring. I have everything figured except the overload circuit. The two terminals at the bottom of the heaters are labeled X and Y. They ohm open and I can't figure out how to trip the overload circuit to verify if there is a contact that operates. My question is how does the overload circuit work and what contact should I use to drop the contacter out of one phase draws to much current. Thanks

 

[Lucky]

Does one of the wires from X or Y go to the starter contactor? Is the contactor 120 or 240VAC? The contacts you are ohming as open are likely a set of Auxiliary contacts that close when the starter pulls in.

 

[simme]

Well, it looks old and corroded. Here is some general information for a low voltage (480) motor. A 3 phase electrically controlled starter will have a manual disconnect section (3 blade type contacts) so that the power can be turned/locked off. Then a contactor section with 3 electrically engaged contacts to switch the power to the motor on and off - driven by an electrical coil (solenoid). Generally the control circuit will be 120 volt produced by a 480/120 transformer in the starter enclosure (example diagrams attached below show full voltage control circuits instead). Last section is the overload protection. Small 120 and 240 motors have internal overload protection (klixon) that is a contact that opens to turn off the power if the motor overloads/overheats. Larger 3 phase motors do not have internal klixon protection. That is done by the heaters and the overload relay/contact. The starters come in various sizes (capacities) (0, 1, 2, 3, etc). There is a max HP for each size starter and a range of motor horsepowers that match to a starter size. Then the heaters have to be selected based on the motor fla (full load amps). Change an existing motor to a smaller hp and you will need to make changes to the heaters in order to have overload protection. Change an existing motor to a larger hp and you will need to make changes to the heaters or else the motor will trip too early. Starter size, fuses, heaters and overload all depend on motor hp.
The heater/overload section has a contact that opens when any phase/heater detects excessive current flow (more than the max capacity of the motor for simplicity). To prevent the motor from burning up. That overload contact needs to be wired into the control circuit. The control circuit generally will have a start button that closes momentarily to start the motor. When the motor coil (solenoid) "pulls-in", an aux contact on the contactor will close to "seal-in" the control circuit so the motor continues to run after you release the start button. To stop the motor, press the momentary stop button which opens to "drop-out" the contactor and the seal-in contact. That overload contact is wired in series with the starter coil (solenoid) to "drop-out" the contactor and seal-in if the motor is pulling too many amps. The reason they are called heaters - the current/amps for the 3 phases (motor leads) flow through the 3 heaters and the heaters generate a little heat proportional to the current flow. The overload relay senses the heat. Heaters are selected and overload relay is set to "trip" based on that amount of heat corresponding to max amp flow to the motor. Generally have to reset the overload relay after a trip in order to close the overload contact.

 

[Lucky]

If it's got a 120v coil break the neutral wire through the O/L contact block. If it's a 240v coil break either of the coil wires through the O/L contact block. Most starters come prewired to do this. It's not that hard. If you want a 3 wire control start stop station that's easy too, it's what the open X and Y contacts are for. Good luck and hope you get it sorted out