Put the two pole breaker that supplies the device as close to the unit as possible. If you ever find the breaker tripped replace the unit, don't reset the breaker thinking that the protector still works.
In order to know if it has tripped I install wire nuts and splice it on circuits already in use so if it does trip the user will know that it has tripped and the protector has did its job and needs replacing.
You may also want to look at the breaker type device that one just replaces two breakers with. They all have close to the same protection values.