Payne PG9MAB Series A Installation Manual page 21

Table 1—Minimum Free Area Required for Each Combustion Air Opening or Duct to Outdoors
TWO HORIZONTAL DUCTS
(1 SQ. IN./2,000 BTUH) (1,100 SQ. MM/KW)
FURNACE
INPUT
Free Area of
(BTUH)
Opening and Duct
(Sq. In.)
44,000 22
66,000 33
88,000 44
110,000 55
132,000 66
154,000 77
EXAMPLES: Determining Free Area
FURNACE WATER HEATER
110,000 +
66,000 +
88,000 +
Table 2—Minimum Space Volumes for 100% Combustion, Ventilation and Dilution Air from Outdoors
OTHER THAN FAN-ASSISTED TOTAL
(1,000'S BTUH GAS INPUT RATE)
ACH
30
0.60 1,050
0.50 1,260
0.40 1,575
0.30 2,100
0.20 3,150
0.10 6,300
0.00 NP
3. ONE OUTDOOR OPENING requires:
a. 1 square inch of free area per 3,000 Btuh (734 mm
b. Not less than the sum of the areas of all vent connectors in the space.
The opening shall commence within 12" (300 mm) of the ceiling. Appliances in the space shall have clearances of at least 1" (25 mm)
from the sides and back and 6" (150 mm) from the front. The opening shall directly communicate with the outdoors or shall communicate
through a vertical or horizontal duct to the outdoors or spaces (crawl or attic) that freely communicate with the outdoors.
Indoor Combustion Air© NFPA & AGA
Standard and Known-Air-Infiltration Rate Methods
Indoor air is permitted for combustion, ventilation, and dilution, if the Standard or Known-Air-Infiltration Method is used.
WARNING: CARBON MONOXIDE POISONING HAZARD
Failure to supply outdoor air via grilles or ducts could result in death and/or personal injury.
Many homes require air to be supplied from outdoors for furnace combustion, ventilation, and dilution of flue gases.
The furnace combustion air supply must be provided in accordance with this instruction manual.
The Standard Method:
1. The space has no less volume than 50 cubic feet per 1,000 Btuh of the maximum input ratings for all gas appliances installed in the space
and
2. The air infiltration rate is not known to be less than 0.40 air changes per hour (ACH).
The Known Air Infiltration Rate Method shall be used, if the infiltration rate is known to be:
1. Less than 0.40 ACH and
2. Equal to or greater than 0.10 ACH
Infiltration rates greater than 0.60 ACH shall not be used. The minimum required volume of the space varies with the number of ACH and shall
be determined per Table 2 or Equations 1 and 2. Determine the minimum required volume for each appliance in the space and add the volumes
together to get the total minimum required volume for the space.
(1 SQ. IN./3,000 BTUH) (734 SQ. MM/KW)
Round Duct
(in. Dia)
6
7
8
9
10
10
TOTAL INPUT
30,000 = (140,000 divided by 4,000)
40,000 = (106,000 divided by 3,000)
30,000 = (118,000 divided by 2,000)
40 50
1,400 1,750
1,680 2,100
2,100 2,625
2,800 3,500
4,200 5,250
8,400 10,500
NP NP
SINGLE DUCT OR OPENING
Free Area of
Round Duct
Opening and Duct
(in. Dia)
(sq In.)
14.7
22
29.3
36.7
44
51.3
= 35.0 Sq. In. for each two Vertical Ducts or Openings
=
=
(1,000'S BTUH GAS INPUT RATE)
44 66
3
Space Volume (ft )
1,100 1,650
1,320 1,980
1,650 2,475
2,200 3,300
3,300 4,950
6,600 9,900
NP NP
2
/kW) for combined input of all gas appliances in the space per Table 1 and
—21—
TWO OPENINGS OR VERTICAL DUCTS
(1 SQ. IN./4,000 BTUH) (550 SQ. MM/KW)
Free Area of
Opening and Duct
(Sq In.)
5 11
6 16.5
7 22
7 27.5
8 33
9 38.5
35.3 Sq. In. for a Single Duct or Opening
59.0 Sq. In. for each of two Horizontal Ducts
FAN-ASSISTED TOTAL
88 110 132
2,200 2,750 3,300
2,640 3,300 3,960
3,300 4,125 4,950
4,400 5,500 6,600
6,600 8,250 9,900
13,200 16,500 19,800
NP NP
Round Duct
(In. Dia)
4
5
6
6
7
8
154
3,850
4,620
5,775
7,700
11,550
23,100
NP NP