Viking VGR30, Service Manual

Page: 12 / 40

12
COMBUSTION OF GAS (CONTINUED)
It is vital that an appliance venting system do its
job. The importance of providing enough fresh
air to the room in which and appliance is
located can not be stressed too strongly.
Carbon monoxide is a toxic gas. It can cause
death if enough of it is inhaled. This gas has no
odor, color or taste, so that it cannot be detected
by bodily senses. Inhaled carbon monoxide is
absorbed into the blood. It combines with
hemoglobin in the blood to a much greater extent
than oxygen and
remains in the blood longer
than oxygen does. In doing so, it acts to reduce
the oxygen-carrying function of the blood. Thus,
a person exposed to carbon monoxide can die lf a
lack of oxygen.
Carbon monoxide is only one product of
incomplete combustion. ALDEHYDES, another
class of compounds, also may be formed in
incomplete combustion. While carbon monoxide
is odorless, Aldehydes have a sharp, penetrating
odor. They are readily detected be smell, even at
very low concentrations. The odor of aldehydes
differs from odorants added to natural gas and the
two should not be confused. The absence of
aldehydes does not assure that carbon monoxide
is not present. However, if the odor of aldehydes
is present, then carbon monoxides almost always
will be present, aldehydes themselves also are
toxic.
H. GAS BURNER OPERATION - A gas burner is
a device to burn gas under control to produce
useful heat.
Primary air is brought into the burner from
outside the appliance at atmosphere pressure.
The gas jet streaming from the orifice draws or
injects primary air into the burner.
PRIMARY AIR: Air which is mixed with gas
before the gas leaves a burner port to burn.
SECONDARY AIR: Air externally supplied to
a burner flame at the point of combustion.
I.
BURNER COMPONENTS
Gas Orifice - An opening or hole, regulates or
limits the amount of gas flowing to a burner. Gas
flow rate (volume) depends on the size of the
orifice (hole) and gas pressure at the inlet of the
orifice.
Air Shutter - This is used to adjust the size of
the openings to control primary air flow.
Venturi Throat - A section in a pipe or a burner
body that narrows down and then flares out again.
This neck helps maintain a more constant primary
air injection.
Mixing Tube - Serves to carry the air-gas mixture
from the venturi throat to the burner head.
Burner Head - Contains the burner ports, and
provides uniform distribution of the air-gas
mixture to those ports.
Burner Ports - Distributes flames to provide good
heat transfer. They spread the flames so they can
be reached by secondary air. They provide
stable, blue flames.