WARNING: This heater shall not be installed in a confined space or unusually tight construc- tion unless provisions are provided for adequate combustion and ventilation air.
Today’s homes are built more energy efficient than ever. New materials, increased insulation and new construction methods help reduce heat loss in homes. Home owners weather strip and caulk around windows and doors to keep the cold air out and the warm air in. During heating months, home owners want their homes as airtight as possible.
While it is good to make your home energy efficient, you need fresh air. All fuel-burning appliances need fresh air for proper combustion.
Supplying Adequate Ventilation
This appliance must be installed in an unconfined space.
The following information will help you classify your space and provide adequate ventilation for complete combustion.
An Unconfined Space has a minimum volume of 50 cubic feet for each 1000 BTU/Hr input rating of all appliances in the space. (4.8 M3 per kw), (cubic feet equals length x width x height of space).
A Confined Space has a volume of less than 50 cubic feet for each 1000 BTU/Hr input rating of all appliances in the space, (4.8M3 per kw), (cubic feet equals length x width x height of space).
Determining if You Have a Confined or Un- confined Space
Use this worksheet to determine if you have a confined or unconfined space.
Space: Includes the room in which you will install heater plus any adjoining rooms with doorless passageways or ventilation grills between the rooms.
1.Determine the volume of the space (length x width x height). Length x Width x Height = _____cu. ft. (volume of space)
Example: Space size 25’ (length) x 25’ (width) x 8’ (ceiling height) = 5,000 cu. ft. (volume of space)
If additional ventilation from adjoining room(s) is supplied with grills or doorless openings, add the volume of these rooms to compute the total volume of the applicable space.
2.Divide the space volume by 50 cubic feet to determine the maximum BTU/Hr the space can support.
________(volume of space) ÷ 50 cu. ft. = (Maximum BTU/ Hr the space can support.
Example: 5,000 cu. ft. (volume of space) ÷ 50 cu. ft. = 100 or 100,000 (maximum BTU/Hr the space can support)
3.Add the BTU/Hr of all gas burning appliances in the space.
| Gas range | BTU/Hr | |
| Vented gas heater | | BTU/Hr |
| Gas fireplace logs | | BTU/Hr |
| Other gas appliances* + | BTU/Hr |
| Total | | = | BTU/Hr |
Example: | Gas range | | 60,000 BTU/Hr |
| Vent-free logs | + | 29,000 BTU/Hr |
| Total | = | 89,000 BTU/Hr |
*Do not include direct-vent gas appliances. Direct-vent draws combustion air from the outdoors and vents to the outdoors.
4.Compare the maximum BTU/Hr the space can support with the actual amount of BTU/Hr used.
__________ BTU/Hr (maximum the space can support)
__________ BTU/Hr (actual amount of BTU/Hr used)
Example: 100,000 BTU/Hr (max. the space can support) 89,000 BTU/Hr (actual amount of BTU/Hr used)
The space in the above example is an unconfined space because the actual BTU/Hr used is less than the maximum BTU/Hr the space can support. If the space had been confined, your options would be as follows:
A.Rework worksheet, adding the space of an adjoining room. If the extra space provides an unconfined space, remove door to adjoining room or add ventilation grills between rooms. See Ventilation Air From Inside Build- ing.
B.Install a lower BTU/Hr heater, if lower BTU/Hr size makes room unconfined.
Converting Confined Space to Unconfined Space
Additional volume to convert a confined to an unconfined space could come from an adjoining space. When using an adjoining space, you can 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 and 3, Figure 2), or remove the door into the adjoining room.
Ventilation Air From Outdoors for Unusually Tight Construction
WARNING: If the area in which the heater may be oper- ated is smaller than that defined as an unconfined space or if the building is of unusually tight construction, provide adequate combustion and ventilation air by one of the methods described in the National Fuel Gas Code, ANSI Z223.1/NFPA 54, Section 5.3 or applicable local codes.
Unusually tight construction is defined as construction where:
a.walls and ceilings exposed to the outside atmosphere have a continuous water vapor retarder with a rating of one perm (6 X 10.11 kg per pa-sec-m2) or less with openings gasketed or sealed and
b.weather stripping has been added on openable windows and doors and
c.caulking or sealants are applied to areas such as joints around window and door frames, between sole plates and floors, between wall-ceiling joints, between wall panels, at penetrations for plumbing, electrical and gas lines and at other openings.
If your home meets all of the three criteria above, you must provide additional fresh air.
You may provide two permanent openings: one within 12” of the ceiling and one within 12” of the floor. Connect these items directly to the outdoors or spaces open to the outdoors. These spaces include attics and crawl spaces. 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.
IMPORTANT: Do not provide openings for inlet or outlet air into attic if attic has a thermostat-controlled power vent. Heated air entering the attic will activate the power vent.
