Determining The Type Of Heater Location Space; Ventilation Air - Mr. Heater MHBF30NGT Installation Instructions And Owner's Manual

installed in that space, and an unconfined space as a
space whose volume is not less than 50 cubic feet per
1,000 Btu per hour (4.8 m
input rating of all appliances installed in that space.
Rooms communicating directly with the space in which
the appliances are installed*, through openings not fur-
nished with doors, are considered a part of the uncon-
fined space.
*Adjoining rooms are communication only if there
are doorless passageways or ventilation grills be-
tween 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: If the area in which the heater may be
operated is smaller than defined as an unconfined
space or if the building is of unusually tight con-
struction, provide adequate combustion and ventila-
tion air by the methods described in the National
Fuel Gas Code, NFPA 54/ ANSI Z223.1, Section
5.3 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 fire-
place 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
Unvented Natural Gas Fired Room Heater
3
per kW) of the aggregate
40,000 Btu/hr
20,000 Btu/hr
=60,000 Btu/hr
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 venti-
lation grills between the rooms. See Ventilation Air
From Inside Building (Fig. 2).
B. Vent room directly to the outdoors. See Ventilation
Air From Outdoors (Fig. 3).
C. Install a lower Btu/hr heater if lower Btu/hr size
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.

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 adjoin-
ing 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 ventila-
tion grills or ducts.
Or remove
Ventilation door into
Gills into
Adjoining
Adjoining
Room -
Room - Option 3
Option 1
WARNING: Rework worksheet, adding the space
of the adjoining unconfined space. The combined
space must have enough fresh air to supply all ap-
pliance in both spaces.
4
Installation Instructions and Owner's Manual
12"
Ventilation Gills into
Adjoining Room - Option 2
12"
Figure 2.