First, you do a phone screening with an HR rep. Next, you are invited to an on-site interview.
This onsite interview was very informal. Leave all your typical "tell me about yourself" interview preparation at the door. Do expect to be 100% gun-ho about HVAC or you won't get hired. They are looking for engineers that will require the bare minimum amount of training possible.
The interview is conducted by senior management engineers where the HR rep waits outside for the interview to be over.
Later you have a 1:1 meeting with the HR Rep discussing how the prior meeting went and are offered an internship instead if one does not have the necessary experience in HVAC.