The main differences between a conventional furnace and a high efficiency condensing furnace are the heat exchanger technology used to extract heat from the combustion process, the method of bringing combustion air to the furnace and the method used to exhaust the combustion gases. As a result, the high efficiency condensing furnace has a few more troubleshooting considerations than its conventional furnace cousin.
In addition to the possible furnace and ignition troubleshooting issues discussed in the tutorials Troubleshooting a Conventional Gas Furnace and Troubleshooting an Electronic Ignition Furnace, this tutorial will discuss additional troubleshooting and repair issues you should consider related to the venting and condensate drainage of a direct vent (two-pipe) high efficiency condensing furnace.
This tutorial will cover the following problems and issues:
- Weak Flame or Combustion Problems
- Intake Air Vent Obstruction
- Exhaust Gas Recirculation
- Furnace Will Not Ignite
- Clogged Condensate Drain (debris, improper draining, frozen condensate)
- Clogged Flue Vent
- Testing a Pressure Switch