||There are three basic types of Gas Fired Warm Air furnaces.
Each type is defined by the direction of airflow thru the furnace as follows:
- A Horizontal warm air furnace is used in a reclining position. The airflow is from side to side. This style of furnace is usually installed in crawl spaces with a shallow ceiling height.
- An Upflow warm air furnace is the most commonly installed type of warm air furnace. The airflow is in an upward direction.
- A Downflow warm air furnace has the air flowing downward over the heat exchanger.
This type of furnace is mostly used when the ductwork is installed into a slab.
Central air conditioning, air cleaners, filters, etc. can be installed on each type of furnace.