Reds
Member
I just bought a Siemans motor starter for my 7.5 hp 3 phase compressor. But it came with the contactor and overload relay installed but no overload relays. If I read correctly the overload relay is a bimetal strip that connects the contactor to the overload control below the contactor. I believe the strip is activated when it heats up because siemans calls them "overload relay heaters". I am not sure what size overload relays to order . My motor tag shows 22.5 FLA (full load amps?). I can order the heater strips in various FLA ratings but I believe that I need a "heater" with more than the FLA due to startup current. The FLA is 22.5 and I was considering ordering heater strips rated for either 24.8 or 27.4 amps. 25 amps would be a 15% increase in amperage to account for startup current. I don't want the heaters to be tripping every time that it starts and at the same time I don't want to cook the motor if I have a problem. Any suggestions on what amps the overload relay should trip at? Any help would be appreciated.
