PG92MSA: Installation, Start-up, Operating and Service and Maintenance Instructions
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
9
The requirements for combustion and ventilation air depend upon
whether or not the furnace is located in a space having a volume of at
least 50 cubic feet per 1,000 BTUh input rating for all gas appliances
installed in the space.
• Spaces having less than 50 cubic feet per 1,000 BTUh (4.8 cubic
meters per kW) require the Outdoor Combustion Air Method.
• Spaces having at least 50 cubic feet per 1,000 BTUh (4.8 cubic meters
per kW) may use the Indoor Combustion Air, Standard or Known Air
Infiltration Method.
Outdoor Combustion Air Method
1. Provide the space with sufficient air for proper combustion,
ventilation, and dilution of flue gases using permanent horizontal or
vertical duct(s) or opening(s) directly communicating with the
outdoors or spaces that freely communicate with the outdoors.
2. Fig. 6 illustrates how to provide TWO OUTDOOR OPENINGS,
one inlet and one outlet combustion and ventilation air opening, to
the outdoors.
a. One opening MUST commence within 12 in. (300 mm) of the
ceiling and the second opening MUST commence within 12 in.
(300 mm) of the floor.
b. Size openings and ducts per Fig. 6 and Table 4.
c. TWO HORIZONTAL DUCTS require 1 sq. in. (645 sq. mm) of
free area per 2,000 BTUh (1,100 mm2/kW) of combined input
for all gas appliances in the space per Fig. 6 and Table 4.
d. TWO OPENINGS OR VERTICAL DUCTS require 1 sq. in.
(645 sq. mm) of free area per 4,000 BTUh (550 mm2/kW) for
combined input of all gas appliances in the space per Fig. 6 and
Table 4.
Table 4 – Minimum Free Area Required for Each Combustion Air Opening or Duct to Outdoors
EXAMPLES: Determining Free Area
Table 5 – Minimum Space Volumes for 100% Combustion, Ventilation and Dilution Air from Outdoors
NP = Not Permitted
WARNING
!
CARBON MONOXIDE POISONING HAZARD
Failure to follow this warning could result in personal injury or death.
The operation of exhaust fans, kitchen ventilation fans, clothes dryers,
attic exhaust fans or fireplaces could create a NEGATIVE PRESSURE
CONDITION at the furnace. Make-up air MUST be provided for the
ventilation devices, in addition to that required by the furnace. Refer to
the Carbon Monoxide Poisoning Hazard warning in the venting section
of these instructions to determine if an adequate amount of make-up air
is available.
FURNACE INPUT
(BTUH)
TWO HORIZONTAL DUCTS
(1 SQ. IN./2,000 BTUH)
(1,100 SQ. MM/KW)
SINGLE DUCT OR OPENING
(1 SQ. IN./3,000 BTUH)
(734 SQ. MM/KW)
TWO OPENINGS OR
VERTICAL DUCTS
(1 SQ. IN./4,000 BTUH)
(550 SQ. MM/KW)
40,000*
20 (12904) 5 (127) 14 (8696) 5 (127) 10 (6452) 4 (102)
60,000
30 (19355) 6 (152) 20 (13043) 5 (127) 15 (9678) 5 (127)
80,000
40 (25807) 7 (178) 27 (17391) 6 (152) 20 (12904) 5 (127)
100,000
50 (32258) 8 (203) 34 (21739) 7 (178) 25 (16130) 6 (152)
120,000
60 (38709) 9 (229) 40 (26087) 7 (178) 30 (19355) 6 (152)
FURNACE WATER HEATER TOTAL INPUT
100,000 + 30,000 = (130,000 divided by 4,000) = 32.5 Sq. In. for each two Vertical Ducts or Openings
60,000 + 40,000 = (100,000 divided by 3,000) = 33.3 Sq. In. for each Single Duct or Opening
80,000 + 30,000 = (110,000 divided by 2,000) = 55.0 Sq. In. for each two Horizontal Ducts
OTHER THAN FAN-ASSISTED TOTAL
(1,000’S BTUH GAS INPUT RATE)
FAN-ASSISTED TOTAL
(1,000’S BTUH GAS INPUT RATE)
ACH
30 40 50 40 60 80 100 120
Space Volume Ft
3
(M
3
)
0.60
1,050 (29.7) 1,400 (39.6) 1,750 (49.5) 1,400 (39.6) 1,500 (42.5) 2,000 (56.6) 2,500 (70.8) 3,000 (84.9)
0.50
1,260 (35.6) 1,680 (47.5) 2,100 (59.4) 1,680 (47.5) 1,800 (51.0) 2,400 (67.9) 3,000 (84.9) 3,600 (101.9)
0.40
1,575 (44.5) 2,100 (59.4) 2,625 (74.3) 2,100 (59.4) 2,250 (63.7) 3,000 (84.9) 3,750 (106.1) 4,500 (127.3)
0.30
2,100 (59.4) 2,800 (79.2) 3,500 (99.1) 2,800 (79.2) 3,000 (84.9) 4,000 (113.2) 5,000 (141.5) 6,000 (169.8)
0.20
3,150 (89.1) 4,200 (118.9) 5,250 (148.6) 4,200 (118.9) 4,500 (127.3) 6,000 (169.8) 7,500 (212.2) 9,000 (254.6)
0.10
6,300 (178.0) 8,400 (237.8) 10,500 (297.3) 8,400 (237.8) 9,000 (254.6) 12,000 (339.5) 15,000 (424.4) 18,000 (509.2)
0.00
NP NP NP NP NP NP NP NP
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