6
L o c h i n v a r
D E S I G N E R
’
S
G U I D E
C O P P E R
-
F I N
I I
W A T E R
H E A T E R
6 1 5 - 8 8 9 - 8 9 0 0
COMBUSTION & VENTILATION AIR
Provisions for combustion and ventilation air
must
be in accordance with Section 5.3,
Air for Combustion and Ventilation, of the
latest edition of the
National Fuel Gas
Code, ANSI Z223.1
; in Canada, the latest
edition of
CGA Standard B149 Installation
Code for Gas Burning Appliances and
Equipment
; or applicable provisions of the
local building codes.
The equipment room
must
be provided with
properly sized openings to assure adequate
combustion air and proper ventilation when
the unit is installed with conventional venting
or sidewall venting.
If air is taken directly from outside
the building with no duct,
provide two
permanent openings:
A.
Combustion air opening with a
minimum free area of one square inch per
4000 Btu input (5.5cm
2
per kW).
This opening
must
be located within 12
”
(30 cm) of the bottom of the enclosure.
B.
Ventilation air opening with a minimum
free area of one square inch per 4000
Btu input (5.5cm
2
per kW). This opening
must
be located within 12
”
(30cm) of the
top of the enclosure.
If combustion and ventilation air is
taken from the outdoors using a
duct to deliver the air to the
mechanical room,
each of the two
openings should be sized based on a
minimum free area of one square inch
per 2000 Btu input (11cm
2
per kW).
If air is taken from another interior
space,
each of the two openings
specified above should have a net free
Lochinvar
1.
2.
3.
EXAMPLE OF
SIZING FOR
COMBUSTION
& VENTILATION
AIR OPENINGS
(WATER HEATER
WITH 2,070,000
Btu/hr INPUT):
When combustion and
ventilated air is taken
from directly outside the
building (FIG. 4), divide
the total BTU’s by 4,000.
This yields 517.5 sq.in.
of “Free Area” without
restriction.
(2,070,000 ÷ 4000 =
517.5 sq.in.)
Since the air opening is
50% closed due to
screens and louvers, the
total opening must be
multiplied by 2.
(517.5 sq. in. x 2 =
1,035 sq.in.)
This project requires one
Ventilation Air Opening
with net “Area” of
1,035 square inches with
louver dimensions of 30
”
x 35
”
and one
Combustion Air Opening
with net “Area” of
1,035 square inches with
louver dimensions
of 30
”
x 35
”.
(FIG. 4) COMBUSTION AIR DIRECT FROM OUTSIDE
(FIG. 5) COMBUSTION AIR THROUGH DUCTWORK
(FIG. 6) COMBUSTION AIR FROM AN
INTERIOR SPACE
CAUTION: Under no circumstances should
the equipment room be under a negative
pressure when atmospheric combustion
equipment is installed in the room.
