I passed HVAC and Refrig. first time. Studied since labor day, probably 240+ hours going hard every day of the week. I must say that I tried to solve way too many MERM problems. Spent needless time studying statics and some materials stuff early on and wasted like 2-3 weeks in the process. 6 minute solutions was critical to my success!
For future HVAC & Refrigeration examinees; I think I have a blueprint for success. Don't waste your time bogging down in merm! Focus on 6 minute solutions, practice exams, and MERM's Fluids, Thermo (minus combustion stuff; not helpful for exam though enriching), and HVAC section; finally bring ASHRAE handbooks! All of them and be familiar with them! Also take PPI's practice exam. It is mega hard but will get you in shape for passing. You will pass if you do well at nailing those topics. Don't spend a lot of time on other MERM topics many of which you probably did not cover in your undergrad classes.
I'm better at self-studying and usually find that more productive than classes for me. If you are a class person by all means. If you are a self-study person, follow the blueprint above.