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Unusually tight construction is defined as con-
struction where:
a. wall and ceilings exposed to the outside
atmosphere have a continuous water vapor
retarder with a rating or one perm or less with
openings gasketed or sealed, and
b. weather stripping has been added on oper-
able 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 penetra-
tions for plumbing, electrical, and gas lines,
and at other openings.
Use the following equations to determine if
you have a confined or unconfined space.
1. Determine the volume of space — ft
Length x Width x Height = _____
(Include adjoining rooms with doorless pas-
sageways or ventilation grills between
rooms.)
Example: 24' (L) x 16' (W) x 8' (H) = 3072
ft
3
2. Divide the volume of space by 50 ft
determine the maximum BTU/Hr the space
can support.
______ (volume of space – ft
(Maximum BTU/Hr the space can support)
3
Example: 3072 ft
/ 50 ft
or 61,440 BTU/Hr the space can support.
3. Add the BTU/Hr of all the fuel burning appli-
ances in the space.
Vent-Free heater
Gas appliance #1*
Gas appliance #2
+ _______ BTU/Hr
Total = _______ BTU/Hr
Example:
VF6000 Vent-free heater 32,000
Gas appliance #1
(water heater)
Total = 66,000
* Do not include direct-vent gas appliances.
Direct-vent is sealed combustion and draws
combustion air from the outdoors.
4
4. Compare the maximum BTU/Hr the space
can support with the actual amount of BTU/
Hr used.
_________ BTU/Hr
_________ BTU/Hr
Example:
61,440
66,000
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 sup-
port. You must provide additional fresh air.
WARNING: IF THE AREA IN WHICH THE
3
.
HEATER MAY BE OPERATED IS SMALLER
THAN THAT DEFINED AS AN UNCON-
ft
3
FINED SPACE, PROVIDE ADEQUATE
COMBUSTION AND VENTILATION AIR BY
ONE OF THE METHODS DESCRIBED IN
THE NATIONAL FUEL GAS CODE, ANSI
Z223.1 1992, SECTION 5.3 OR APPLI-
CABLE LOCAL CODES.
3
to
Your options are:
a. Rework equations adding the space of ad-
joining room(s). If the extra volume provides
3
)/ 50 ft
3
=
an unconfined space, then remove door or
add ventilation grills between rooms. Refer
to National Fuel Gas Code, ANSI Z223.1
3
= 61.44
1992, Section 5.3.
b. Vent room directly to the outdoors. Refer to
National Fuel Gas Code, ANSI Z223.1 1992,
Section 5.3.
_______ BTU/Hr
c. Install a lower BTU/Hr heater, such as the
_______ BTU/Hr
25,000 BTU/Hr, to make the area an uncon-
fined space.
If the actual BTU/Hr used is less than the
maximum BTU/Hr the space can support, then
the space is an unconfined space. You will need
BTU/Hr
no additional fresh air ventilation for an uncon-
34,000
BTU/Hr
fined space.
BTU/Hr
NOTE: DIAGRAMS & ILLUSTRATION NOT TO SCALE.
(max. the space can support)
(actual amount of BTU/Hr used)
BTU/Hr
(max. the space can support)
BTU/Hr
(actual amount of BTU/Hr used)
LOCATION OF FIREPLACE
Carefully select the best location for installation
of your VF5000 and VF6000 series Unvented
Room Heater. The following factors should be
taken into consideration:
• Clearance to side wall, ceiling, woodwork
and windows.
• Location must not be affected by drafts
caused by kitchen exhaust fans, return air reg-
isters for forced air furnaces/air conditioners,
windows or doors.
• Installation must provide adequate ventila-
tion and combustion air.
• Do not install the VF5000 and VF6000 series
heaters in a sleeping room or bathroom.
• Never obstruct the front opening of the
heater or restrict the flow of combustion and
ventilation air.
• This appliance may be installed in an after-
market manufactured (Mobile) Home, where
not prohibited by state or local codes.
*Aftermarket: Completion of sale, not for pur-
pose of resale, from the manufacturer.
• Minimize modifications to existing construc-
tion. Refer to Figure 1 for location suggestions.
Figure 1
To ensure even heat distribution, it is best to
position the heater centrally against the long-
est wall of the room. Make sure there is ad-
equate ventilation where the heater is installed.
The gas appliance will shut off if the oxygen
level falls below 18.0%.
These appliances are uniquely suited for in-
stallations requiring a utility shelf positioned
directly above the fireplace. Utility shelves like
these are commonly used for locating televi-
sion sets and decorative plants.
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