Determining The Type Of Heater Location Space - Mr. Heater MHVFBF20NGBT Operating Instructions And Owner's Manual

*Adjoining rooms are communication only if there
are odorless passageways or ventilation grills
between them.
DETERMINING THE TYPE OF HEATER
LOCATION SPACE:
Use this method to determine if you have a confined or
unconfined space.
Note: the space includes the room in which you
install heater plus any adjoining rooms with doorless
passageways or ventilation grills between the rooms.
1. Find the volume of the space by multiplying room
length x width x height.
Example: Space size 18ft (length) x 18ft. (width) x 8ft.
(height) = 2592
If additional ventilation to adjoining room is supplied
with grills or openings, add the volume of these rooms
to the total volume of the space.
2. Divide the space volume by 50 cubic feet to deter-
mine the maximum Btu/hr the space can support.
Example: 2592 cu.ft. (volume of space) / 50 cu.ft. =
51.8 or 51,800 (maximum Btu/hr the space
can support)
WARNING: This heater shall not be installed in a
room or space unless the required volume of indoor
combustion air is provided by the method described
in the National Fuel Gas Code, ANSI Z223.1/NFPA
54, the International Fuel Gas Code, or applicable
local codes.
3. Add the Btu/hr of all the fuel-burning appliances
in the space such as, Vent–free heater, Gas water
heater, Gas furnace, Vented gas heater, Gas
fireplace logs, and Other gas appliances*
*Do not include direct-vent gas appliances. Direct-
vent draws combustion air from the outdoors and
vents to the outdoors.
Example: Gas water heater
Vent Free Heater +
Total
4. Compare the maximum Btu/hr the space can support
with the actual amount of Btu/hr used.
Example: 51,800 Btu/hr (maximum Btu/hr the
space can support)
60,000 Btu/hr (Actual amount of Btu/hr
used)
The space in the above example is a confined
space because the actual Btu/hr used is more than
the maximum Btu/hr the space can support.
You must provide additional fresh air. Your options
are as follows:
A. Rework worksheet, and the space of an adjoining
room. If the extra space provides an unconfined
space, remove door to adjoining room or add
ventilation grills between the rooms. See Ventilation
Air From Inside Building (Figure 2).
Unvented Natural Gas Vent Free Room Heaters
B. Vent room directly to the outdoors. See Ventilation
C. Install a lower Btu/hr heater if lower Btu/hr size
VENTILATION AIR
Ventilation from Inside Building
This fresh air would come from an adjoining unconfined
space. When ventilation to an adjoining unconfined
space, you must provide two permanent openings:
one within 12" of the ceiling and one within 12" of
the floor on the wall connecting the two spaces (see
options 1 & 2 of fig. 2). You can also remove door into
adjoining room (see option3, fig 2). Follow the National
Fuel Gas Code NFPA 54/ ANSI Z223.1, Section 5.3,
Air for Combustion and Ventilation for required size of
ventilation grills or ducts.
Ventilation
Gills into
Adjoining
Room -
Option 1
40,000 Btu/hr
20,000 Btu/hr
=60,000 Btu/hr
OUTLET
AIR
INLET
AIR
5
Installation Instructions and Owner's Manual
Air From Outdoors (Figure 3).
makes room unconfined.
If actual Btu/hr used is less than the maximum Btu/
hr the space can support, the space is an uncon-
fined space. You will need no additional fresh air
ventilation.
Figure 2.
Or remove
Ventilation Gills into
door into
Adjoining Room - Option 2
Adjoining
Room -
Option 3
OUTLET AIR
Figure 3.
12"
12"
VENTILATION AIR
VENTILATED
ATTIC
TO ATTIC
TO CRAWL
SPACE
VENTILATION CRAWL SPACE