VENTED versus VENT-FREE Gas
Fireplace Products
General: Gas Log sets are a very convenient replacement
for all the hassles of burning wood: Procuring, chopping, stacking, hauling,
spiders, bugs, sparks, ashes, creosote, chimney fires, cleaning and waiting for
the embers to die down before going to bed, to name a few. Gas logs sets,
whether vented or vent-free types, provide instant on and off, no sparks, ready
fuel supply and look good for the greater proportion of time when a fire is not
burning. While a fireplace should not to be viewed as a primary heat
source, it can be a fine supplemental heater, providing warmth to a particular
room. Additionally, whether vented or vent-free, it is a great source of
emergency heat in the event of a power outage, as gas log sets derive their
power from the pilot light and/or batteries.
Vented gas logs, which we first made in 1958, are much healthier than burning
wood, as there are no wood particulates that can cause irritation. They
are designed with a burner that produces a yellow, smoky, wood-like flame, so
they must be used in a fireplace with a working chimney, one which exhausts all
of the products of combustion. The products of combustion only enter the living
space if the chimney does not work properly, thus the occupants are unaffected
by the by-products of the gas log during normal use. Unfortunately, most
fireplace designs, while being efficient in exhausting the combustion products,
are very inefficient as heaters, as much of the heat goes up the chimney rather
than into the room. That led to the development of vent-free set.
In 1994, Rasmussen became the sixth US manufacturer to make a vent-free gas log
set. Since then, we have created a variety of vent-free fireplace
products, including our Chillbuster line with many styles of logs and burner
arrangements; CoalFire coal basket fires for use in smaller Victorian and coal
fireplaces; and the Alterna VF line of contemporary gas fires, which include
the FireBalls, FireShapes, FireStones and Fire Glitter. Rasmussen
has served on technical and sub-committees that write and revise the national
standard, ANSI Z1.11.2, to which all vent-free heaters are certified, and an
active member of the Vent-free Gas Products Alliance, our industry group that
is committed to developing and maintaining markets for vent-free heaters.
Please consider
the following additional factors when deciding between vented pan burner pan
burner and heat-effect gas log sets:
CHILLBUSTER and ALTERNA VF:
These sets are designed, certified and manufactured by Rasmussen to two
nationally recognized consensus standards:
ANSI Z21.11.2 Unvented Heaters and Z21.60 Decorative Gas
Appliances. This permits our Chillbuster
Heat-Effect Gas Log Sets and ALTERNA VF Vent-Free Contemporary Gas Fires to be
sold and used in any jurisdiction, regardless of their position on vent-free
use or the position of the chimney damper.
Safety:
Rasmussen only sells safe products and has been doing so for over 100
years. You enhance and ensure the safety
of the product by properly installing and operating it in accordance with the
instruction manual and applicable codes and ordinances. All heat-effect gas heaters are equipped with
oxygen depletions sensors (ODS) and safety control valves to shut down the unit
in case of unhealthful oxygen levels or in the event of an interruption in gas
supply or flameout. Vented pan burner
sets may be ordered with safety control valves to shut down the unit in the
event of an interruption in gas supply or flameout.
Efficiency: Heat-effect sets are the best products if you
desire a supplemental and/or emergency heat source for the room in which the
fireplace is located. Since the damper
may be closed, there is no heat loss up the chimney. Please note that heat-effect heaters, like
all gas burning appliances, require fresh air for proper combustion and
customer satisfaction. With heat-effect
heaters used in the vent-free mode, the products of combustion vent into the
living space; with vented pan burner gas logs, the products of combustion vent
up the chimney. Some people are more
sensitive to the natural odor associated with the burning of gas, which can be
exacerbated with a lack of adequate fresh air in heat-effect applications.
IMPORTANT INFORMATION about “Partially
Vented” or “Reduced Vent” Gas Log Sets:
A few
manufacturers of gas log sets have introduced gas log sets that purport
to allow the consumer to close the damper to a minimum opening while enjoying
rich, yellow flames and more heat in the room.
The basis for their claim is a chart in the National Fuel Gas Code that
specifies minimum venting area based on BTUs consumed. The manufacturers reduced the BTU use from
their standard fully vented gas log sets to a point where the chart allows for
a smaller damper opening, which would keep more of the heat in the room. The
PROBLEM with these sets is that they all
produce soot and the soot is either going to go up the chimney or out
into the room. The market experience is
that the specified “reduced vent” openings are not sufficient to always exhaust
all of the products of combustion up the chimney, therefore putting soot into
the living space (which can be harmful to health and furnishings). The
only TRUE SOLUTION for someone who wants to close the damper to a
setting less than full open is to use a HEAT EFFECT gas log set (such as a
CHILLBUSTER) that has been certified to ANSI Z21.11.2 Unvented Heater Standard,
since these sets are not permitted to
produce any soot.
Aesthetics: "Beauty is in
the eyes of the beholder." Rasmussen manufactures what we consider to be
the best looking vented pan burner and heat-effect gas log sets available. The national standard for vent-free heaters
is very restrictive in ways that limit the flame appearance (40,000 BTU/hour
maximum input; lowest level of carbon monoxide allowed of any gas burning
appliance, no carbon (soot) formation).
The flame characteristics of a vented pan burner pan burner set are
fuller (more BTUs) and more wood-like in appearance. Since the yellow, smoky flame produces carbon
(soot), and the standards to which these sets are certified allow more carbon
monoxide than heat-effect sets, the damper must be open when operating a vented
pan burner pan burner set. Since most
fireplaces are very inefficient with the damper open, much of the heat is lost
up the chimney. However, the ceramic
logs radiate some heat into the room, as do the burning embers. Additionally, one gets a warm feeling from
the presence of the flame itself.
Soot:
Heat-effect gas log sets are not permitted to soot by the vent-free
standard to which they are certified.
This makes them well suited for “smoking” fireplaces (those that do not
draw or vent properly). Vented pan burner gas logs sets are designed to burn
with a yellow smoky flame that produces soot.
Vented pan burner sets require that the chimney flue exhaust al of the
products of combustion up the chimney, otherwise the soot will enter into the
living space. This is the trade-off for
the rich, luminous flame.
Product Size Selection:
Heat-effect gas log sets are available in 18-, 24- and 30-inch sizes
with various log appearances and burner styles.
Vented pan burner log sets are available in sizes ranging from 12- to
96-inches, with custom sets available for large and unusual fireplaces. We currently offer 14 styles of vented pan
burner log sets as well as many contemporary styles, such as FireBalls,
FireShapes, FireStones and FireGlitter.
Summary:
Heat-effect gas log heaters (like CHILLBUSTER) give you the best heat
value from your gas dollar spent. They
also give you flexibility of venting, as you can safely use them with no or
little damper opening, as desired and permitted by local jurisdiction. The vented pan burner set better approximates
the aesthetics of a wood fire. There are
many more size, burner style and control options for vented sets, as well as
the ability to have custom solutions for large and unusual fireplaces. The choice is yours based on your needs and
desires.
Additional Information about Vent-Free Sets
ANSI Z21.11.2 (the national Unvented Heater standard to which all vent-free
products are certified) is the most restrictive of all gas appliance standards,
which allows the least amount of Carbon Monoxide (CO) (200 ppm air free) of any
gas burning appliance. By contrast, the standard for a kitchen range,
which is also an unvented appliance, allows up to 800 ppm air free. In
addition to the vent-free standard, all Rasmussen vent-free sets are certified
to the vented decorative standard (ANSI Z21.60), which allows you to use the
damper closed, open or anywhere in between, depending on your preference and
local restrictions.
The ANSI
Z21.11.2 standard also requires that all vent-free heaters be equipped with an
Oxygen Depletion Sensor (ODS). An ODS is a system that includes a
quick-acting thermocouple and a calibrated pilot. The pilot becomes unstable at
lowered levels of oxygen, causing the thermocouple to close down the flow of
gas through the valve to the burner. Normal room air contains 20.9% oxygen. Death
or serious injury occurs at oxygen levels of about 15%. An ODS is required by
the standard to shut down the system by 18.0% oxygen.
By the ANSI
standard, vent-free gas log sets must be designed so that they do not produce
soot.
Rasmussen
vent-free sets use a state-of-the-art opposed-louver lanced-port burner.
This type of burner is very forgiving when operated under adverse conditions,
such as improper log placement or drafts. Such conditions result in the
flame impinging on the logs, which cause soot from our competitors'
punched-port burners, but operate clean with the Rasmussen burners.
Initial
certification testing is extremely rigorous. We are subject to periodic
unannounced inspections by our certification agency. Rasmussen, unlike
most of our competitors, gas tests every vent-free burner to ensure gas
tightness of all fittings and proper operation.
Vent-free gas
log sets, like all gas burning appliances (including vented gas log sets),
require fresh air for proper combustion and customer satisfaction. When
used without adequate fresh air, such as in tightly constructed homes or in
homes in which all avenues of air infiltration are sealed off, certain odors
can become a nuisance. The sources of these odors are impurities in the air
in the living space (such as cigarette smoke, pet hairs, off-gassing from
paint, carpets, laminates, glues textiles, etc.) or from the natural odor
associated with the burning of gas.
Water vapor is
a natural product of combustion. Without adequate fresh air, it can build
up to the point of being noticeable and unpleasant. It can mix with
impurities from other sources to cause a brown film on walls and windows.
As you can
see, fresh air is important for a satisfactory experience with a vent-free
heater. If you have any doubt, you should use either a vented set with
the damper fully open, or a vent-free set with the damper cracked open to
permit some of the products of combustion to exhaust. One big advantage
of the vent-free sets is that you can change the damper position to help strike
the best balance between heat and indoor air quality issues.
The 40,000 BTU/hour maximum gas input for
vent-free heaters restricts the largest width of a set to 30-inches.
In the vent-free, the log stacks are set in their log
placement to provide the best combustion. You do not have the flame
playing off of the logs like that of vented sets, where the logs are loose and
can be arranged as desired.
Life is full of trade-offs. The limitations set by ANSI Z21.11.2 allow
you to operate the set with the damper closed, thus virtually eliminating the
heat loss up the chimney. But, they just don't look as good as the vented
sets. But if you choose the fuller flame and more random and full log
stacks of the vented sets, you lose much of the heat from the requirement that
the damper be wide open when burning.