Owner`s manual

32925-3-0115 Page 17
Watervaporisaby-productofgascombustion.Anunventedroom
heater produces approximately one (1) ounce (30ml) of water for
every 1,000 BTU's (.3KW's) of gas input per hour.
Unvented room heaters are recommended as supplemental heat (a
room) rather than a primary heat source (an entire house). In most
supplemental heat applications, the water vapor does not create a
problem.Inmostapplications,thewatervaporenhancesthelow
humidity atmosphere experienced during cold weather.
The following steps will help insure that water vapor does not
becomeaproblem.
1. Be sure the heater is sized properly for the application, including
amplecombustionairandcirculationair.
2. Ifhighhumidityisexperienced,adehumidiermaybeusedto
help lower the water vapor content of the air.
3. Do not use an unvented room heater as the primary heat
source.
Thisheatershallnotbeinstalledinaconnedspaceorunusually
tight construction unless provisions are provided for adequate
combustionandventilationair.

Aconnedspaceisanareawithvolumelessthan50cubicfeetper
1,000Btuhofthecombinedinputratesofallappliancesdrawing
combustionairfromthatspace.Smallareassuchasequipment
roomsareconnedspaces.Furnacesinstalledinaconnedspace
which supply heated air to areas outside the space must draw return
air from outside the space through tightly sealed return air ducts. A
connedspacemusthave2openingsintothespaceforcombustion
air.Oneopeningmustbewithin12inchesoftheceilingandthe
othermustbewithin12inchesoftheoor.Therequiredsizingof
theseopeningsisdeterminedbywhetherinsideoroutsideairis
usedtosupportcombustion,themethodbywhichtheairisbrought
tothespace(verticalorhorizontalduct)andbythetotalinputrate
of all appliances in the space.
Unusually Tight Construction
Theairthatleaksarounddoorsandwindowsmayprovideenough
freshairforcombustionandventilation.However,inbuildingsof
unusually tight construction, you must provide additional fresh air.
      

a. Walls and ceilings exposed to the outside atmosphere have
a continuous water vapor retarder with a rating of one perm
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
oors,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. See  page
18.

Usethisworksheettodetermineifyouhaveaconnedorunconned
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 16 ft. (length) x 10 ft. (width) x 8 ft. (ceiling
height) = 1,280 cu. ft. (volume of space)
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 determine the
maximum BTU/Hr the space can support.
(volume of space) ÷ 50 cu. ft. = (maximum
BTU/Hr the space can support)
Example: 1,280 cu. ft. (volume of space) ÷ 50 cu. ft. = 25.6 or
25,600 (maximum BTU/Hr the space can support)
3. AddtheBTU/Hrofallfuelburningappliancesinthespace.
Vent-free heater
BTU/Hr
Gas water heater BTU/Hr
Gas furnace BTU/Hr
Vented gas heater BTU/Hr
Gasreplacelogs BTU/Hr
Other gas appliances* + BTU/Hr
Total = BTU/Hr
Example: Vented gas heater 20,000 BTU/Hr
Vent-free heater + 18,000 BTU/Hr
Total = 38,000 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:
25,600 BTU/Hr (maximum the space can support)
38,000 BTU/Hr (actual amount of BTU/Hr used)
WARNING
Iftheareainwhichtheheatermaybeoperatedissmallerthanthat
denedasanunconned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, Air for Combustion and Ventilation,
orapplicablelocalcodes.
WATER VAPOR: A BY-PRODUCT OF UNVENTED ROOM HEATERS
