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5
UVLC Series
Fresh Air Requirements
for Combustion and Ventilation
If your home meets all of the above criteria, you must
provide additional fresh air for the appliance as detailed
on Page 6.
If your home does not meet the above criteria, follow
the procedure below.
Determine If You Have a Confined
or Unconfined Space
Use the following formula to determine if you have a
confined or unconfined space.
Space is defined as the room in which you will install
the heater, plus any adjoining rooms with doorless pas-
sageways or ventilation grilles between the rooms.
The National Fuel Gas Code defines a confined space
as a space whose volume is less than 50 cubic feet per
1,000 BTU per hour input rating (4.8m
3
per Kw) of the
aggregate (total) input rating of all appliances installed
in that space and an unconfined space as a space
whose volume is not less than 50 cubic feet per 1,000
BTU per hour (4.8m
3
per Kw) of the aggregate input
rating of all appliances installed in that space. Rooms
communicating directly with the space in which the ap-
pliances are installed, through openings not furnished
with doors, are considered a part of the unconfined
space.
1. Determine the volume of space (length x width x
height). Include adjoining rooms connected by doorless
passageways or ventilating grilles.
Example: A room that is 18’ x 12’ x 8’ has a volume of
1728 cubic feet. An adjoining open kitchen that is 10’
x 12’ x 8’ has a volume of 960 cubic feet. An adjoining
open dining room is 12’ x 12’ x 8’ with a volume of 1152
cubic feet. The total volume is 3840 cubic feet.
2. Divide the volume of space by 50 cubic feet. The
result is the maximum BTU/hour the space can support.
Example: 3840 cubic feet divided by 50 = 76.8 or
76,800 BTU/hour.
3. Add the BTU/hour ratings of all fuel-burning applianc-
es installed in the same space, including the following:
Gas Water Heater Gas Furnace
Gas Fireplace Logs Vent-free Gas Heater
Vented Gas Heater* Other Gas Appliances*
* Do not include Direct-vent appliances as these
use outdoor air for combustion and vent to the
outdoors.
Modern construction standards have resulted in homes
that are highly energy-efficient and that allow little heat
loss. Your home needs to breathe, however, and all
fuel-burning appliances need fresh air to function prop-
erly and safely. Exhaust fans, clothes dryers, fireplaces,
and other fuel burning appliances all use the air inside
the building. If the available fresh air supply is insuffi-
cient to meet the demands of these appliances, prob-
lems can result.
The vent-free logs sets have specific fresh air require
-
ments. You must determine that these requirements
will be met within the space where the appliance will be
installed. The following information will help you ensure
that adequate fresh air is available for the heater to
function properly.
Provide for Adequate Ventilation
Any space within a home can be classified in these
categories:
1) Unusually tight construction
2) Confined space
3) Unconfined space.
First, determine which classification defines the intend-
ed installation space.
Unusually Tight Construction
You must provide additional fresh air if the space falls
into this classification. Unusually Tight Construction is
defined as construction wherein:
a. Walls and ceilings exposed to the outside atmo-
sphere have a continuous water vapor barrier with a
rating of one perm or less, with openings gasketed or
sealed, and
b. weather stripping has been added on openable win-
dows and doors and
c. caulking or sealants are applied to areas such as
joints around windows and door frames, between sole
plates and floors, between wall and ceiling joints, be-
tween wall panels, at penetrations for plumbing, electri-
cal, and gas lines, and at all other openings.
This heater must have fresh air for proper opera-
tion. If it does not, poor fuel combustion could
result. Read the following instructions to ensure
proper fresh air supply for this and other fuel-
burning appliances in your home.
WARNING
Installation Requirements