Enerco MHVFB10LP Ventilation AIR, Ventilation from Inside Building, Ventilation from Outdoors

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 construc- tion, provide adequate combustion and ventilation 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 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	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 ventila- tion 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 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.

		12”
Ventilation	Or remove	Ventilation Gills into
		Adjoining Room -
Gills into	door into
	Adjoining	Option 2
Adjoining
	Room -
Room -
	Option 3
Option 1
		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 appliance in both spaces.

		VENTILATION AIR
OUTLET AIR			VENTILATED
			ATTIC
OUTLET				TO ATTIC
AIR				TO CRAWL
INLET				SPACE
AIR
	VENTILATION234CRAWL SPACE

Figure 3.

Ventilation from Outdoors

If necessary provide extra fresh air by using ventilation grills or ducts. Connect these items directly to the outdoors or spaces open to the outdoors. These include attics* and crawl spaces. Follow the National Fuel Gas

4Installation instructions and Owner’s Manual