I had a new furnace put in today. Its a frigidaire 80,000 BTU force hot air unit. I was told by the installer that my gas line (3/4") is not big enough and that the line needs to open up to 1 1/2" after the main. I guess I am confused because main gas line coming up through the ground is only 3/4" so how would opening up to a 1 1/2" pipe increase flow. The main has a T connector on it with one (3/4")line going to another thermopride unit which works fine and the other 3/4" line going to my hot water heater and new furnace. The hot water heater works fine. I have no other appliances using the gas. The gas man said I had 8 something or other coming from the main which is more than enough. Anyone know what is going on here.