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PG80MSU: Installation, Start-up, Operating and Service and Maintenance Instructions
*Minimum opening size is 100 in.2 with minimum dimensions of 3 in. (76 mm).
*Minimum of 3 in. (76 mm), when type -B1 vent is used.
Fig. 8 – Air for Combustion, Ventilation, and Dilution from Indoors
c. TWO HORIZONTAL DUCTS require 1 square inch of free area
per 2,000 BTUh (1,100 mm2/kW) of combined input for all gas
appliances in the space per
d. TWO OPENINGS OR VERTICAL DUCTS require 1 square
inch of free area per 4,000 BTUh (550 mm2/kW) for combined
input of all gas appliances in the space per
Table 2 – 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
(BTUh)
Free Area of
Opening and Duct
Sq. In (Sq. mm)
20 (12904)
40,000
30 (19355)
60,000
40 (25807)
80,000
100,000
50 (32258)
EXAMPLE: Determining Free Area
FURNACE
WATER HEATER
100,000
+
30,000
60,000
+
40,000
+
30,000
80,000
Table 3 – Minimum Space volumes for 100% combustion, Ventilation, and Dilution from Indoors
OTHER THAN FAN-ASSISTED TOTAL
(1,000'S BTUh GAS INPUT RATE
*
ACH
30
1,050
0.60
1,260
0.50
0.40
1,575
0.30
2,100
3,150
0.20
6,300
0.10
NP
0.00
*. Air Changes/Hour
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
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
Fig. 7
and
Table
2.
Fig. 7
and
Table
Round Duct
Opening and Duct
In. (mm) Dia
Sq. In (Sq. mm)
5 (127)
6 (152)
7 (178)
8 (203)
TOTAL INPUT
=
(130,000 divided by 4,000)
=
(100,000 divided by 3,000)
=
(110,000 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
3. ONE OUTDOOR OPENING requires:
a. 1 square inch of free area per 3,000 BTUh (734 mm2/kW) for
combined input of all gas appliances in the space per
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.
CARBON MONOXIDE POISONING HAZARD
Failure to follow this warning could result in death and/or personal
A03175
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.
2.
SINGLE DUCT OR OPENING
(1 SQ. IN./3,000 BTUh)
(734 SQ. MM/KW)
Free Area of
Round Duct
In. (mm) Dia
14 (8696)
5 (127)
20 (13043)
5 (127)
27 (17391)
6 (152)
34 (21739)
7 (178)
=
32.5 Sq. In. for each two Vertical Ducts or Openings
=
=
(1,000'S BTUh GAS INPUT RATE)
40
Space Volume (ft.3)
1,000
1,200
1,500
2,000
3,000
6,000
NP
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:
7
WARNING
!
TWO OPENINGS OR
VERTICAL DUCTS
(1 SQ. IN./4,000 BTUh)
(550 SQ. MM/KW)
Free Area of
Opening and Duct
Sq. In (mm)
10 (6452)
15 (9678)
20 (12904)
25 (16130)
33.3 Sq. In. for each Single Duct or Opening
55.0 Sq. In. for each two Horizontal Ducts
FAN-ASSISTED TOTAL
60
80
1,500
2,000
1,800
2,400
2,250
3,000
3,000
4,000
4,500
6,000
9,000
12,000
NP
NP
Table 2
and
Round Duct
In. (mm) Dia.
4 (102)
5 (127)
5 (127)
6 (152)
100
3,300
3,960
4,950
6,600
9,900
19,800
NP
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