Motor Overload Relay Resetting Opinions
Motor Overload Relay Resetting Opinions
(OP)
I typically use motor AC drive to control a AC motor. I have an application that I do not need a AC drive, but I am using an overload relay. My question is how do people in the industrial or similar industry typically deal with the motor overload resetting. Do you require the overload to be reset and the machine to be restarted to restart the motor. According to NEC 430 section you can allow a motor to overload and reset automatically if there will be no hazard that will exist. On the overload relays that I was looking at it has a reset button that must be manually reset, but the motor will start immediately when the reset is pressed (is this automatically starting not acceptable?) unless the monitor the extra auxiliary contact is used to stop the motor control (relay, contactor) by control the relay or monitoring through PLC.
According to NFPA 79 (Industrial machinery) section 7.3.2 it states "Resetting of the overload device shall not restart the motor." I do not understand how this can be met when some motors have a thermal overload built into the motor that reset automatically.
So my question is do you typically use a motor overload with all motors and monitor a auxiliary contact of the motor overload. So when the motor overload trips it will stop the motor control (relay, contactor). I am trying to look to see what is the industry standard?
Any help will be great appreciated.
According to NFPA 79 (Industrial machinery) section 7.3.2 it states "Resetting of the overload device shall not restart the motor." I do not understand how this can be met when some motors have a thermal overload built into the motor that reset automatically.
So my question is do you typically use a motor overload with all motors and monitor a auxiliary contact of the motor overload. So when the motor overload trips it will stop the motor control (relay, contactor). I am trying to look to see what is the industry standard?
Any help will be great appreciated.





RE: Motor Overload Relay Resetting Opinions
Having to open a live panel to perform the reset... is unacceptable. It either needs an external reset button or the entire panel should be brought down (powered off), opened, reset, panel closed, powered-up.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Motor Overload Relay Resetting Opinions
"Will work for (the memory of) salami"
RE: Motor Overload Relay Resetting Opinions
RE: Motor Overload Relay Resetting Opinions
"..the more, the merrier" Genghis Khan
RE: Motor Overload Relay Resetting Opinions
You then need to look at the application. Emergency pumps to empty tanks where there is a danger of engulfment or boiler feed water pumps may require an auto restart due to the fact that if they don't the risk of it not running exceeds the fact that it has to be manually reset. Signs stating that it may automatically restsrt need to be in place just like air compressors that turn on and off due to air pressure.
Train the staff. Do a small test for competancy. Get them to sign Annual reinforcement, again with signatures.
RE: Motor Overload Relay Resetting Opinions