Johnson Controls YP8C/YPLC*MP FAN-ASSISTED Combustion System, Ambient Combustion Air Supply

368262-UIM-B-1008

FAN-ASSISTED COMBUSTION SYSTEM

This appliance is equipped with an integral mechanical means to draw products of combustion through the heat exchanger.

Ambient Combustion Air Supply

This type installation will draw the air required for combustion from within the space surrounding the appliance and from areas or rooms adjacent to the space surrounding the appliance. This may be from within the space in a non-confined location or it may be brought into the furnace area from outdoors through permanent openings or ducts. A single, properly sized pipe from the furnace vent connector to the out-

Combustion Air Source From Outdoors

The blocking effects of louvers, grilles and screens must be given con- sideration in calculating free area. If the free area of a specific louver or grille is not known, refer to Table 7, to estimate free area.

Table 7: Estimated Free Area

Wood or Metal	Wood 20-25%*
Louvers or Grilles	Metal 60-70% *
Screens+	1/4” (0.635 cm)
	mesh or larger 100%

doors must be provided. For upflow models combustion air is brought	*	Do not use less than 1/4”(0.635 cm) mesh
into the furnace through the unit top panel opening.	+	Free area of louvers and grille varies widely; the installer should follow
		louver or grille manufacturer’s instructions.

COMBUSTION

AIR

FIGURE 26: Combustion Airflow Path Through The Furnace Casing to the Burner Compartment

This type of installation requires that the supply air to the appli- ance(s) be of a sufficient amount to support all of the appliance(s) in the area. Operation of a mechanical exhaust, such as an exhaust fan, kitchen ventilation system, clothes dryer or fireplace may cre- ate conditions requiring special attention to avoid unsatisfactory operation of gas appliances. A venting problem or a lack of supply air will result in a hazardous condition, which can cause the appli- ance to soot and generate dangerous levels of CARBON MONOX- IDE, which can lead to serious injury, property damage and / or death.

An unconfined space is not less than 50 cu.ft (1.42 m3) per 1,000 Btu/ hr (0.2928 kW) input rating for all of the appliances installed in that area.

Rooms communicating directly with the space containing the appli- ances are considered part of the unconfined space, if openings are fur- nished with openings or louvers.

A confined space is an area with less than 50 cu.ft (1.42 m3) per 1,000 Btu/hr (0.2928 kW) input rating for all of the appliances installed in that area. The following must be considered to obtain proper air for combus- tion and ventilation in confined spaces.

Dampers, Louvers and Grilles (Canada Only)

1.The free area of a supply air opening shall be calculated by sub- tracting the blockage area of all fixed louvers grilles or screens from the gross area of the opening.

2.Apertures in a fixed louver, a grille, or screen shall have no dimen- sion smaller than 0.25” (0.64 cm).

3.A manually operated damper or manually adjustable louvers are not permitted for use.

4.A automatically operated damper or automatically adjustable lou- vers shall be interlocked so that the main burner cannot operate unless either the damper or the louver is in the fully open position.

When a Category I furnace is removed or replaced, the original venting system may no longer be correctly sized to properly vent the attached appliances.

An improperly sized vent system can cause CARBON MONOXIDE to spill into the living space causing personal injury, and or death.

Table 8: Unconfined Space Minimum Area in Square Inch

BTUH Input Rating				Minimum Free Area in Square Feet
					Required for Each Opening
60,000						60 (387 cm2)
80,000						80 (516 cm2)
100,000						100 (645 cm2)
120,000						120 (742 cm2)
Table 9: Free Area
BTUH Input			Minimum Free Area Required for Each Opening
			Horizontal Duct			Vertical Duct or	Round Duct
Rating						Opening to Outside
			(2,000 BTUH)				(4,000 BTUH)
						(4,000 BTUH)
60,000			30 in2 (193 cm2)			15 in2 (97 cm2)	5” (13 cm)
80,000			40 in2 (258 cm2)			20 in2 (129 cm2)	5” (13 cm)
100,000			50 in2 (322 cm2)			25 in2 (161 cm2)	6” (15 cm)
120,000			60 in2 (387 cm2)			30 in2 (193 cm2)	7” (18 cm)
EXAMPLE:		Determining Free Area.
Appliance			1 Appliance			2 Total Input
100,000	+		30,000 = (130,000 ⎟ 4,000) = 32.5 Sq. In. Vertical
Appliance			1 Appliance			2 Total Input
100,000	+		30,000 = (130,000 ⎟ 2,000) = 65 Sq. In. Horizontal

20 Johnson Controls Unitary Products