My Carrier furnace has two pvc pipes that go through the basement wall and up the side of the house. At the top of the pvc pipe the intake has one 90 degree fitting so the opening is pointed straight out to the side of the vertical pipe. The exhaust pipe has two 90 degree fittings at the top of the pipe, which gives a 180 degree turn and the exhaust opening is pointed straight down. My neighbor says this is the opposite of his and the exhaust opening should point to the side while the intake opening should point down. Can someone tell me which is correct? The furnace was installed before I bought the house, so I don't have a manual and could not find the answer on the net. Thanks.