The Parts Of A Residential Heating and Cooling System

Think of a furnace as your lungs. What goes out of the unit must be brought back into the unit in order to function properly and increase the unit's lifespan. The air distributed into the home is referred to as "supply air". The supply air is forced by the blower (fan) through the heat exchanger and/or evaporator coil to be "conditioned". Then through the plenum it goes an into our main supply duct. (Trunk-lines, photo #3.)

The supply duct is sized based on the amount of air it must move. This trunk sizing will shrink as you move down the line since air will be fed out to individual "supply runs" (photo #5)along the way. Fittings called "transitions" (photo #4) are used to make this size adjustment; thus the name transition. (Transitioning from one size to another.) These fittings are also used on the "return air" side of the system as the same idea applies in reverse when bringing air back to the system. You see in photo #4 that transitions are not the only type of duct fitting. Various fittings are used to maneuver around obstacles or rise and lower to avoid beams and piping as well. The possibilities are endless but these basic terms and diagrams cover the majority of what you'd see in the field or average home.

NOTE: See the handle on the pipe in photo #5...this is the handle of a "damper". Dampers are used to close off air flow to specific areas of a home. If the handle is in line with the flow of air, it is open. If positioned sideways, it is closed. Sometimes dampers are used in the trunk-line as well to shut down whole portions of a home or to just balance the airflow better.

Once the air is pushed through the trunk-lines and into the supply runs, it will be released through the register "boot". These boots come in many various shapes and sizes depending on what is needed based on the room above in relation to the structure of the home. Though they very in size and shape, they fall into one of 3 main categories. Straight boots, ell boots and end boots.

Now that the conditioned air has reached its' destination and kept us cool or warm, it must head back to the furnace. Remember, it's like a lung...imagine breathing out all day without inhaling...not good. Though the fan is capable of inhaling and exhaling simultaneously, it must do both or it will "starve" for air and burn up long before its' time.

The air will leave the room via return air registers that draw the air back down the wall and into return air bays. These bays are simply the space created by the joists in the basement which are "panned off" (photo #7) to seal the air going back to the return air trunk. (photo #3)

NOTE: Sealing off return air is important. You don't want to draw unpleasant air from the basement, bathrooms, or kitchens throughout the entire house.

The last piece of our hvac technician jobs sacramento puzzle for now is the "flue" or chimney. In photo #8 I've provided an example of the flu piping used in a high efficiency system. This PVC piping is usually 2 -3 inches in diameter and typically vents out the side of the home. (Vertically through the roof is possible though.) This is the piping that will condensate and is to be installed pitched downward toward the furnace. (1/4" per foot is recommended.) In a lower efficiency system, steel piping is still used and usually vented into a masonry chimney and out through the roof. (Note: A chimney should be lined with a steel liner or at least clay tile. Flu gas is corrosive and will deteriorate the mortar over time.)

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Comments: 1
  • #1

    heating furnace (Monday, 24 July 2017 13:27)

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