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Installed a Ducane 95% high condensing gas furnace. The unit will fire and run for about five minutes. The unit will shut down and indicate a bad pressure switch. I changed the pressure switch and still the same thing. The gas company came out to check the gas service and all is well there. Any suggestions? Thanks
 

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heatman
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check to make sure correct sizeing of exhaust and supply air.if not correct will trip sensor.long sweep elbows very important.
 

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ldr
I see that your proffesion listed is heating, however the question you ask and the actions you have performed are not consistant with a trained professional.
Please read the installation COMPLETELY and perform all steps EXACTLY as they are explained.
At the very least, contact a local dealer and explain you situation, im sure someone would be willing to come out and point you in the right direction.
You should also have a building permit. in this case a mechanical inspector will come out and point all the things that you have done that will not work.
scooter
 

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Furnace problem

Check that venting is sized and installed properly. Exhaust must be sloped back to furnace 1/4"/ft without any sags at any point. Good idea to support every 4 feet since it could sag as the pipe warms up. Check condensate drain is sloped, vented and trapped if required, check installation manual for details.
There are millions of perfectly good pressure switches in the landfill.
Installation is almost always the problem.
 

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It seems like the limit switch is opening on the furnace. Generally when a furnace goes off on its high limit is because the airflow is being controlled making the furnace overheat. A limit switch is there to protect the furnace from overheating, the majority causes are either dirt or the blower motor not running up to speed, anything that cuts down on the airflow will cause the high limit switch to open.
 
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