Mr. Heater MHVFB10LP VENTILATION AIR Ventilation from Inside Building, Ventilation from Outdoors

install heater plus any adjoining rooms with door- less 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. =

51.8or 51,800 (maximum Btu/hr the space can support)

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.

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

5.3or 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*

Ventilation Gills into Adjoining Room - Option 1

Or remove door into Adjoining Room - Option 3

12”

Ventilation Gills into Adjoining Room - Option 2

*Do not include direct-vent gas appliances. Direct- vent draws combustion air from the outdoors and vents to the outdoors.

Example:
Gas water heater	40,000 Btu/hr
Vent Free Heater + 20,000 Btu/hr
Total	=60,000 Btu/hr

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 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/

12”

Figure 2

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.­

		VENTILATION AIR
OUTLET AIR			VENTILATED
			ATTIC
OUTLET				TO ATTIC
AIR				TO CRAWL
INLET				SPACE
AIR
	VENTILATION CRAWL SPACE

Figure 3.

Ventilation from Outdoors

If necessary provide extra fresh air by using ventilation grills or ducts. Connect these items directly to the out-

Unvented LP-Gas Fired Buddy Wall-Mount Heater 4 Installation Instructions and Owner’s Manual