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
*Do not include
Example: |
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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.
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Ventilation | Or remove | Ventilation Gills into | |
Adjoining Room - | |||
Gills into | door into | ||
Adjoining | Option 2 | ||
Adjoining | |||
Room - |
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Room - |
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Option 3 |
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Option 1 |
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| 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.
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OUTLET AIR |
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| ATTIC | |||
OUTLET |
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AIR |
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INLET |
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AIR |
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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
