They send an image of their EPA cert to the website to get marked as a professional member. If you don't you show up as a 'regular guest' or something like that.
I opened an account there and as long as you aren't saying you are doing something or asking questions that make it sound like you are installing or modifying equipment or handling gas or refrigerant they are receptive. The moment you ask for the limit of head pressure, they are going to ask for you to become on a pro on the forum and close the thread telling you to come back. You might want to do a search for udarrell He has a website with homeowners in mind and is on multiple sites where DIY guys are and even has a full website at
Scroll to "MY AIR CONDITIONING PAGES using Ctrl+F where he talks about A/C stuff. On that same link go up about a page or two and there are other HVAC forum links that have more DIY friendly members. If you find guys like this they might give a crack at giving you an answer. There are lots of guys who really seem to know their stuff on Youtube, it takes some searching to find them but they are there. I even watched a video of a guy working on the same mid-80's furnace model that I have in my house and he said where the heat exchangers corrode out first and how to clean the burners, burner chamber, and other checks for my furnace. Very helpful but at the same time I know enough not to screw anything up.