Is there a way to tell if a wall is load bearing?

Set up a visit with a professional (contractor or architect) because this is as important as designing your home. You don't want to make a mistake trying to predict what is load bearing and what is not... if you have the blueprints to your house, you could take those to a professional who can read them if you don't know how to read them yourself. The blue prints will show whether or not a wall is load bearing.

If the upright posts are not removed can a loadbearing wall be opened up?

Here are a few links for you.

http://homeguides.sfgate.com/load-bearing-wall-39130.html

https://m.wikihow.com/Tell-if-a-Wall-is-Load-Bearing

https://homebuilding.thefuntimesguide.com/load-bearing-wall/amp/

Generally what you are planning on doing requires a permit, make sure you find out your local building codes. Check your local municipality websites for info.

Are you going to do this yourself?

I called the Town to have them send someone to let me know which walls were load-bearing. It should be a free service and its why you pay taxes, plus they are professionals.

My late husband wanted to use real brick to line the wall and floors around a woodstove and the weight of the bricks had to be okayed by a guy from TownHall.

Most Cities don't send out their employees to explain what a load bearing wall is.... they are there to inspect building as it proceeds to the building plan you submit to get a building permit. You will need usually 2 inspections for this project.

I suggest you have a consult with a construction engineer or a contractor for estimates. Before you hire one, be sure to check them out on the state contractors licensing board to make sure their license is valid, they have no outstanding complaints, have current insurance and worker's comp.

https://www.youtube.com/watch?v=3_Yb6E7XFzU