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Atmospheric Gas
SECTION III: PRE-INSTALLATION (cont.)
NOTE: Locate the heater so it is not subject to physical damage from moving vehicles or
flooding. Do not locate the water heater in a room where swimming pool chemicals or large
quantities of water softener salt are kept. Installing a water heater
in this environment will result in premature failure of tank and
burner components due to corrosion caused by these elements
diffusing into the air.
DO NOT INSTALL THE WATER HEATER ON COMBUSTIBLE
FLOORING.
Place on noncombustible flooring and maintain
clearances prescribed by this manufacturer and per code NFPA 54. If
the water heater must be located on combustible flooring it must be
raised off the floor with a layer of 4'' concrete block laid so the air
holes are aligned as shown in Figure 2. Consult with local code
officials before using this method. Please consult local codes, NFPA
54 and/or contact Bock Water Heaters with questions concerning
proper flooring materials. Leave adequate room for periodic maintenance of heater and burner.
The water heater should be placed as near to the chimney as practical in order to keep vent
connector length to a minimum. Consult National Fuel Gas Code for proper vent configuration.
Minimum clearance to combustible construction is: SIDES 6"; BACK 6"; FRONT 24";
DRAFT HOOD; 18". The installation of this water heater must conform with local
codes and ordinances. In the absence of local codes, the installation must comply
with the National Fire Protection Association (NFPA 54) Code.
COMBUSTION AND VENTILATION AIR
The water heater must be installed in a location with an adequate air supply for combustion,
ventilation and draft control. Unsafe levels of carbon monoxide (CO), condensation and
sooting may result if the room does not have an adequate air supply. See “National Fuel Gas
Code (NFPA 54)” or the discussions of “Unconfined Space” and “Confined Space” below. Poor
ventilation will also result in hot spots around the heater. Temperatures over 90°F near the
water heater generally indicate a lack of ventilation.
UNCONFINED SPACE
Unconfined space is defined by NFPA 54 as a space with a volume greater than 50 cubic feet
(during typical use) per 1000 BTUH of the total combined input of all fuel burning appliances
in the space. Rooms leading directly to the installation space through doors that cannot be
closed can be considered part of the space.
Exception:
Buildings with full vapor barriers, tight
doors and windows or air infiltration rates of less than 0.35 air changes per hour will be
considered a confined space and require additional air supplies.
CONFINED SPACE
Confined space is defined by NFPA 54 as a space with a volume less than 50 cubic feet (during
typical use) per 1000 BTUH of the total combined input of all fuel burning appliances in the
space. Buildings or rooms of unusually tight construction are also considered a confined space.
See
“Unconfined Space:
Exception
”.
When installing fuel burning appliances in a confined space, air must be supplied to that
space from either inside or outside of the building as conditions allow.
A. Inside Air Supply:
A confined space shall be provided with two permanent openings; one
within 12 inches of the top and one within 12 inches of the bottom of the enclosure. These
openings shall lead directly to room(s) of sufficient volume so that the combined volume of
all the space meets the criteria for unconfined space. Each opening shall have a minimum free
area of 1 square inch per 1000 Btu/hr of the combined total input of all fuel burning
appliances in the space. Each opening shall have an area of not less than 100 square inches or
a minimum dimension of not less than 3 inches.
Figure 2