Your second question: Thermal OLs 'open', and the motor starter opens (Off).
First question may require more than the NEC, as staircase pressurization is Building & Fire Safety Codes. I suggest that you contact the local AHJs in whatever area you are working in. My opinion would be no OLs, just short circuit protection as this is a life safety item, perhaps like a fire pump. Just my opinion.
#203396 - 09/27/1112:57 AMStaircase Pressurization Fan Motor Overload
Is there a Thermal Relay in a DOL starter for "staircase pressurization fan"? When motor overload happens,will the Thermal Relay cut off the contactor?
In a Direct On Line starter, your only real protection is thermal via the overloads at the base of the contactor. This should by rights open the control circuit and shut everything off, unless it has been poorly designed or wired.
This is first year apprentice stuff, why do you ask?
#203404 - 09/27/1109:10 AMRe: Staircase Pressurization Fan Motor Overload