Thermal overload relay setting for Ex "eb" motors 1

[NickParker]

For an Ex eb motor, is it necessary for the thermal overload relay to be Ex certified? After inspection, should it be sealed with a sticker to prevent tampering with the settings?

Neither the MCC nor the thermal overload relay is Ex certified. The thermal overload relay is located in the starter drawer within the MCC (installed in a safe location), however the thermal overload relay curve (class 5) is below the tE (safe locked rotor time).

 

[Kiribanda]

Since the motor is located in an area where an explosive hazard is it should have some certification.
So why you are thinking of having the same requirement for the MCC & its components like thermal relay installed in a safe location?

 

[che12345]

"..#1.For an Ex eb motor, is it necessary for the thermal overload relay to e Ex certified? #2.After inspection, should it be sealed with a sticker to prevent tampering with the settings? #3. Neither the MCC nor the thermal overload relay is Ex certified. The thermal overload relay is located in the starter drawer within the MCC.., however the thermal overload relay curve (class 5) is below the tE (safe locked rotor time)"
I have the following opinion for your consideration.
1. Yes, a new designation Ex eb motor (formerly Ex e) should be protected by an Ex certified thermal overload. The Ex eb motor does NOT ensure that it cannot exceed the permissible surface temperature, but the Ex certified thermal overload does.
2. I do NOT locate such requirements. May be there are exceptions, imposed by the owner of the plant.
3. It is usual that MCC and starter with the thermal over-load are away from the motor, which is in the Ex rated area. The thermal over-load should be of the Ex certified type. This is to ensure that OL the tE is < the motor tE. Warning: Check that the OL tE is < motor tE on the name-plate. A Class 5 OL is NOT readily available on the market.
4. BTW: All major European OL OEMs manufacture "special" version OL with characteristics in compliance with ATEX motors.
Che Kuan Yau (Singapore)