trane furnace problem

hvacfreak

I have seen situations like this where water ( condensate ) finds a way into the sampling tubes and wont let the switch close ( proving draft ). You say this only happens when it's cold...just my first thought.

The incorrect termination would allow more water to enter the combustion air pipe as well ( filling bottom of inducer housing ).

If the pipes were too small , this may show itself during cold weather ( I would expect this to show up during mild weather though ). An old bee's nest in the inlet pipe is good for this problem too ( though not cold weather related ).

steve carvelli

trane furnace problem

I installed a trane 90% furnace 4yrs ago. The problem is when it gets cold out, the system drops out and flashes pressure switch problem. I cleaned the condensate trap and all condensate lines are clean and clear. I replaced the pressure switch but it still happens. I noticed when the plumber vented the pvc exhaust pipes, he did go by one of the manufactories suggestions. he did the one where the intake pipe elbows down and the exhaust comes out about a foot and terminates with a 45' elbow. the way it is working, the exhaust pipe comes out of house and elbows down and the intake comes out a foot and terinates with a 45' elbow. it looks like everything is piped correctly, but each pipe is doing the opposite it should be. any suggestions?

Glenn Harrison_2

Look in the intake pipe...

and see if there is any signs of frost or ice. The way you describe the termination your are most likely recirculating exhaust gases into the intake pipe, and when it gets cold the warm gasses hit the cold intake pipe and freeze. If enough frost/ice builds up it will cause the pressure switch fault.

The other thing to check is the pitch and support of the exhaust pipe from one end to the other. If there is a low spot in your exhaust pipe, or not enough pitch to keep the condensate flowing, you will build up water in the exhaust pipe which will also cause the pressure switch fault.

steve carvelli

I didnot notice any ice in the intake pipe, the installed one of the pvc screens. the furnace came back on while I was on the way up to her house, but I will check the level of the pipes. thanks for your help

john_155

what size pipe is used on the vent? how long is the run and how many 45 and 90 are there?

tim smith

Trane furnace & press. switch

Make sure to poke out the sensing ports for the pressure switch on the collector box and wherever else it's tubes connects with a small drill bit or something. Checked combustion fan wheel for any build up. Change the pvc intake and outlet to have the flue blow straight out as it exits the wall and then turn down the comb. air and drop with piece 12" to get separation. Good luck, Tim

burninben

How bout a cracked heat exchanger? Do you have a CO detector?