Should bimetallic overload relays be tested yearly by current injection ?

[gpattu]

Hello!
Rejoining after long time. Pl. let me know any standard available for frequency of current injection testing of bimetallic overload relays ?
Thanks.

 

[oldfieldguy]

One of my clients (in my previous employment with an electrical testing company) had his devices tested in conjunction with this regularly scheduled 3-year maintenance. He included ALL overloads on process motors including the 480-volt equipment. This was a sizable number, and he paid for us to do it.

This was the ONLY one of a long list of clients to do so.

Other clients had us test thermal bimetallic overloads used on 2300 and 4160 motors, but as I got out of the business, most of those devices were being replaced by microprocessor-based protective relays.

old field guy