Thermal Overload Relay Testing
Thermal Overload Relay Testing
(OP)
I am testing Cutler Hammer C306 bi-metallic TOLs. Should the poles be tested individually or in series?
Man is troubled by what might be called the Dog Wish, a strange and involved compulsion to be as happy and carefree as a dog --- James Thurber





RE: Thermal Overload Relay Testing
What are you testing for?
Note that the size of the conductors may affect the calibration. Conductors should be sized based on 75 deg. insulation.
If you test individually the relay should trip early due to differential action. If you test in series you may not identify a late tripping pole.
A complete test would include testing with rated current through two poles and a variable current through the pole under test as well as a test with the same current through all three poles in series. This way you will be able to test both differential action and overload tripping.
However, if you have a nuisance tripping issues, a first, fast test would be all three poles in series at rated current.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Thermal Overload Relay Testing
Man is troubled by what might be called the Dog Wish, a strange and involved compulsion to be as happy and carefree as a dog --- James Thurber
RE: Thermal Overload Relay Testing
Use the same size conductors for the test connections as are used in service. The conductor acts as a heat sink and a different size conductor may bias the results. Probably not much at 300% but using the same size wire removes all doubt.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Thermal Overload Relay Testing
"Will work for salami"
RE: Thermal Overload Relay Testing
Man is troubled by what might be called the Dog Wish, a strange and involved compulsion to be as happy and carefree as a dog --- James Thurber
RE: Thermal Overload Relay Testing
what I meant was that 24 to 209 is acceptable. Anything outside of that is unacceptable and requires further investigation. Could be a test method problem or could be a component issue.
Man is troubled by what might be called the Dog Wish, a strange and involved compulsion to be as happy and carefree as a dog --- James Thurber
RE: Thermal Overload Relay Testing
"Will work for salami"