Garland 40 Series Technical Reference Manual - page 69
Part # GCTRM Rev 3 (12/10/09)
Page 69
Updraft: Excessively low air pressure existing at the outlet of
a chimney or stack which tends to increase the velocity
and volume of gases passing up the stack.
UtilityGases: Natural gas, manufactured gas, liquefied
petroleum gas-air mixtures or mixtures of any of these
gases.
Vent: A device, such as a pipe, to transmit flue products from
an appliance to the outdoors. This term also is used to
designate a small hole or opening for the escape of a fluid
(such as in a gas control or regulator)
Ventgases: Products of combustion from gas appliances
plus excess air, plus dilution air in the venting system
above a draft hood.
Venturi: A section in a pipe or a burner body that narrows
down and then flares out again.
Viscosity:The property of a fluid to resist flow.
YellowTippingofFlames: Too severe a reduction in primary
air also causes its problems. Yellow tipping is one of them.
Flames will eventually become all yellow if no primary air
is supplied. Glowing carbon particles in the flame cause
these yellow tips. Soot will form if these yellow flames
impinge on cooler surfaces. Here again, carbon monoxide
can be produced. Yellow tipping is corrected by the
injection of more primary air.
WaterColumn: Abbreviated as W.C. A unit used for
expressing pressure.