A high-efficiency gas furnace should mean better heating with less energy, which also means lower costs. There are some issues that can affect these furnaces, though, with most problems centered around the complicated vent system that enables the furnace to heat at a more efficient rate.
1. Intake Obstruction
Without a consistent intake of fresh air, the furnace will fail to combust properly and you will get either a weak flame or no flame at all—which means no heat. Intake pipes can be obstructed by any type of debris. Bird and animal nests are common issues if the intake inlet isn't screened to keep them out. Leaves and other debris can also blow into or against the intake and lead to an obstruction. Clearing the obstruction and installing screening will help.
2. Poor Recirculation Configuration
Ideally, the exhaust from the furnace should be placed far enough away from the intake on the exterior of the home so that the intake doesn't draw in the exhaust. If they are too close together, then gases and condensation from the exhaust will recirculate into the intake and affect the rate of combustion. The problem can be dangerous, as well, since you don't want dangerous gases like carbon monoxide recirculating into the home. Your repair tech will need to reconfigure the location of the vents to prevent recirculation.
3. Exhaust Flue Blockages
Much like the intake vent, the exhaust flue can also be prone to blockages. Flues are usually located on the roof, whereas intakes can be placed on a wall. This makes flues even more prone to blockages from bird nests and blown-in debris. The fix is similar to that of the intake. Any obstructions must be removed and then a flue cap or screen should be installed to prevent future issues.
4. Single Vent System Issue
Ideally, a high-efficiency furnace will have two separate pipes for the exhaust flue and intake vent, but some installers use a shared pipe for both. These furnaces are more likely to have issues with recirculation and condensation in the system, which can lead to weak ignition flames and poor heating. Your furnace repair service can install an upgraded system with a separate pipe for exhaust and intake, which should solve the problem.
Contact a furnace repair service if you are having issues with your high-efficiency furnace venting system. Most issues can be quickly addressed so that your furnace works as efficiently as it should.