![background image](http://html.mh-extra.com/html/carrier/58mvb-series/58mvb-series_installation-start-up-and-operating-instructions-manual_2562818019.webp)
When combustion air ducts are used, they must be of the same
cross sectional area as the free area of the openings to which they
connect. The minimum dimension of ducts must not be less than 3
in. (80mm).
Combination of Indoor and Outdoor Air
1. Indoor openings shall compy with the Indoor Combustion
Air Method below and,
2. Outdoor openings shall be located as required in the Outdoor
Combustion Air Method mentioned previously and,
3. Outdoor openings shall be sized as follows:
a. Calculate the Ratio of all Indoor Space volume divided by
required volume for Indoor Combustion Air Method
below.
b. Outdoor opening size reduction Factor is 1 minus the
Ratio in a. above.
c. Minimum size of Outdoor openings shall be the size
required in Outdoor Combustion Air Method above
multiplied by reduction Factor in b. above. The minimum
dimension of air openings shall be not less than 3 in. (80
mm).
INSTALLATION
Step 1—Leveling Legs (If Desired)
When furnace is used in upflow position with side inlet(s), leveling
legs may be desired. (See Fig. 21.) Install field-supplied,
corrosion-resistant 5/16-in. machine bolts and nuts.
NOTE:
The maximum length of bolt should not exceed 1-1/2 in.
1. Position furnace on its back. Locate and drill a 5/16-in.
diameter hole in each bottom corner of furnace. (See Fig. 21.)
Holes in bottom closure panel may be used as guide locations.
2. For each hole, install nut on bolt and then install bolt and nut
in hole. (Install flat washer if desired.)
3. Install another nut on other side of furnace base. (Install flat
washer if desired.)
Fig. 19—Air for Combustion, Ventilation, and Dilution
for Outdoors
A03174
1 SQ IN.
PER
4000
BTUH*
DUCTS
TO
OUTDOORS
1 SQ IN.
PER 4000
BTUH*
CIRCULA
TING
AIR DUCTS
VENT
THROUGH
ROOF
D
B
A
C
E
1 SQ IN.
PER 4000
BTUH*
DUCT
TO
OUTDOORS
CIRCULATING AIR DUCTS
1 SQ IN.
PER 2000
BTUH*
1 SQ IN.
PER 2000
BTUH*
DUCTS
TO
OUTDOORS
12
″
MAX
12
″
MAX
12
″
MAX
Use any of the following
combinations of openings:
A & B C & D D & E F & G
NOTE:
*Minimum dimensions of 3 in.
12
″
MAX
12
″
MAX
OUTDOORS
1 SQ IN.
PER
4000
BTUH*
F
G
CLEAR
ANCE IN FRONT
OF COMB
USTION AIR
OPENINGS SHALL BE
AT LEAST 3 IN.
→
Fig. 20—Air for Combustion, Ventilation, and Di-
lution from Indoors
A03175
CIRCULATING AIR
DUCTS
6" MIN
(FRONT)
†
CIRCULATING AIR DUCTS
VENT THROUGH ROOF
1 SQ IN.
PER 1000
BTUH* IN DOOR
OR WALL
12" MAX
1 SQ IN.
PER 1000
BTUH* IN DOOR
OR WALL
12" MAX
* Minimum opening size is 100 sq in. with
minimum dimensions of 3 in.
†
Minimum of 3 in. . when type-B1 vent is used.
UNCONFINED
SPACE
INTERIOR
HEATED
SPACE
CLEARANCE IN FRONT OF COMBUSTION AIR
OPENINGS
SHALL
B
E
A
T
LEAST 3 IN.
Fig. 21—Leveling Legs
A89014
1
3
⁄
4
″
1
3
⁄
4
″
1
3
⁄
4
″
1
3
⁄
4
″
5
⁄
16
″
5
⁄
16
″
5
⁄
16
″
5
⁄
16
″
19
→