Bryant 140/E series Installation, Start-Up, Operating And Service And Maintenance Instructions page 8

Table 2 – Minimum Free Area Required for Each Combustion Air opening of Duct to Outdoors
TWO HORIZONTAL DUCTS
FURNACE (1 SQ. IN./2,000 BTUH) (1,100 SQ. MM/KW)
INPUT
Free Area of Opening
(BTUH)
and Duct
Sq. In. (Sq. mm)
44,000 22 (14194)
66,000 33 (21290)
88,000 44 (28387)
110,000 55 (35484)
132,000 66 (42580)
154,000 77 (49677)
FURNACE WATER HEATER
110,000 + 30,000
66,000 + 40,000
88,000 + 30,000
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)
30
ACH
1,050
0.60
(29.7)
1,260
0.50
(35.6)
1,575
0.40
(44.5)
2,100
0.30
(59.4)
3,150
0.20
(89.1) (118.9)
6,300
0.10
(178.3) (237.8)
0.00
NP
NP = Not Permitted
(1 SQ. IN./3,000 BTUH) (734 SQ. MM/KW)
Round Duct Free Area of Opening
Dia.
In. (mm) Sq. In. (Sq. mm)
6 (152)
7 (178)
8 (203) 29.3 (18903)
9 (229) 36.7 (23677)
10 (254)
10 (254) 51.3 (33096)
EXAMPLES: Determining Free Area
TOTAL INPUT
= (140,000 divided by 4,000)
= (106,000 divided by 3,000)
= (118,000 divided by 2,000)
40 50
1,400 1,750 1,100
(39.6) (49.5) (31.1)
1,680 2,100 1,320
(47.5) (59.4) (37.3)
2,100 2,625 1,650
(59.4) (74.3) (46.7)
2,800 3,500 2,200
(79.2) (99.1) (62.2)
4,200 3,300
5,250 (148.6)
(93.4)
8,400 10,500 6,600
(297.3) (186.8)
NP NP NP
SINGLE DUCT OR OPENING
Round Duct
and Duct Dia.
In. (mm)
14.7 (9484) 5 (127)
22 (14193) 6 (152)
7 (178)
7 (178)
44 (28387) 8 (203)
9 (229)
= 35.0 Sq. In. for each two Vertical Ducts or Openings
= 35.3 Sq. In. for a Single Duct or Opening
= 59.0 Sq. In. for each of two Horizontal Ducts
FAN-ASSISTED TOTAL
(1,000'S BTUH GAS INPUT RATE)
44 66 88
3 3
Space Volume Ft (M )
1,650 2,200
(46.7) (62.2)
1,980 2,640
(56.0) (74.7)
2,475 3,300
(70.0) (93.4)
3,300 4,400
(93.4) (124.5)
4,950 6,600
(140.1) (186.8)
9,900 13,200
(280.3) (373.7)
NP NP
8
TWO OPENINGS OR VERTICAL DUCTS
(1 SQ. IN./4,000 BTUH) (550 SQ. MM/KW)
Free Area of Opening Round Duct
and Duct Dia.
Sq. In. (Sq. mm) In. (mm)
11 (7096) 4 (102)
16.5 (10645) 5 (127)
22 (14193) 6 (152)
27.5 (17742) 6 (152)
33 (21290) 7 (178)
38.5 (24839) 8 (203)
110 132
2,750 3,300 3,850
(77.8) (93.4) (109.0)
3,300 3,960 4,620
(93.4) (112.1) (130.8)
4,125 4,950 5,775
(116.8) (140.1) (163.5)
5,500 6,600 7,700
(155.7) (186.8) (218.0)
8,250 9,900 11,550
(233.6) (280.3) (327.0)
16,500 19,800 23,100
(467.2) (560.6) (654.1)
NP NP
154
NP