compressor starter overload relay

[Reds]

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.

 

[MEP001]

They're meant to handle startup load - if your voltage is 240 then 25A is correct. If it's 208V you'll need 30A.

 

[wash4me]

Usually the closest overload to fla of the motor is fine. If you are wondering how small you can go just pat an ammeter on it running and see what it reads at full pressure.