Chapter 14 Heating, Ventilation & Air conditioning (hvac) Construction Estimating Prof R. V. Locurcio

Outline HVAC Systems Residential HVAC Systems Commercial HVAC Systems

Definition HVAC systems consist of equipment, ductwork, and piping used to heat and ventilate buildings and to condition (cool and dry) the air. Equipment can be: a furnace, an air-conditioning coil, a compressor, a plenum, a boiler, a tank, a pump, manifolds, outlets, and valves, etc…

HVAC Systems Two types considered Residential

Residential HVAC Systems Two Types Central heating and air-conditioning Hot air systems Hot water systems Steam Radiant heating used only to heat spaces

Central Heating and AC The most common residential HVAC systems Functions to cool and heat spaces System consists of: A furnace supplying heated air through ductwork A main trunk line of rectangular duct Supply lines running from the trunk line to the registers or vents A return air duct returning the air from the rooms to the furnace Metal duct using air between joists and studs. See Fig 14.1 to Fig. 14.4

Figures 14.1 to Fig 14.4

Example 14-1 Determine the HVAC components needed for the residence in figures 14-1 and 14-2. The furnace includes an air-conditioner. A 2”X2” register is required at each base cabinet. A 6”x 18” grille is needed at each return air. Distance top of furnace to the roof is 20 feet. The vent pipe is 4 inches in diameter.

Solution-1 Equipment: a furnace, a coil, a compressor, and a plenum (enclosed space to facilitate air circulation) For the supply trunk: 16 feet of 8”x 12” rectangular duct, two 8”x 12” to 8”x 8” transitions, 17 feet of 8” x 8”, and two 8” x 8” end caps are needed. For the individual supply lines 6-inch 90-degree elbow are needed

View of HVAC System

Plan View of HVAC System

Solution-2 6-inch-diameter duct needed (17 ft + 17 ft + 19 ft + 19 ft + 2ft + 4 ft + 3 ft + 3 ft + 6 ft) = 90 feet For base cabinets: three-6inch 90-degree elbow Three 2” x 12” registers, six 4” x 12” boots, and six-4” x 12” registers For the return air: Two-6” x 18” grilles

Solution-3 Sheet metal: 15 feet of 18-inch-wide (1+4+1+1+7+1) ft Two ea. 8” x 12” end caps 12 feet of 8” x 12” duct, and 8 feet of 12” x 18” duct from the trunk line to the bottom of the furnace.

Solution-4 For the vents: 2 feet above the roof and 4 feet of pipe are needed; Two 4-inch 90-degree single-wall elbows, 4 feet of 4-inch-diameter single wall pipe, 22 feet of 4-inch-diameter double wall pipe, one 4-inch roof flashing, and one 4-inch termination cap. One line set to connect the condenser to the coil, one thermostat, and one roll of wiring are needed.

Radiant Heating Another type of residential heating Uses hot water to warm the floor, which in turn warms the living space. It consists of supply manifold, pump, boiler, return manifold, air ejector, expansion tank, and valves. It cannot be used for cooling purposes Figure 14-6 shows details about radiant heating

Equipment for Radiant Heating

Figure 14-7 Pipe Spacing

HVAC Systems Two types considered Commercial

Commercial HVAC Systems Small commercial buildings often use HVAC systems similar to that of the residential system, using more units as the building gets larger. Larger single-story buildings often use a roof-top units (package units) that heat and cool the air and then distribute it through the building using ductwork. As building gets taller a heat exchanger is used. The heating and cooling is accomplished by heating or cooling water at a central point. Commercial systems may also use chillers, boilers, dampers, fans, and variable-air-volume (VAV) boxes.

Commercial systems

Example 14-4 Determine the HVAC components needed for the commercial HVAC system shown in Figure 14-8. Two feet of 6-inch-diameter flexible duct is used to connect the diffuser to the ductwork. The plenum is used for return air. The existing supply and return lines are made of copper.

Figure 14-8

Figure 14-10

Figure 14.9

RESIDENTIAL HVAC

HVAC Equipment

Basic System

Upflow Furnace

Attic unit

Ductwork-1

Ductwork-2

Ductwork-3

Joining Flex Duct

Ductwork-4

Ductwork-5

AC Coils

Floor Plenum

Questions