im ready for summer
the first section of duct installed on a furnace that connects a furnace to the branch ducts is called the
plenum
the severity of an electrical shock is determined by
intensity of electric current flow and its path through the body
the pilot assembly orifice of a spark ignition furnace is completely clogged. the technician should
replace it
if voltage is applied across 2 speed terminals on a fan motor at the same time, the motor will
short out/burn out
to change the cubic feet per minute (CFM) being delivered by a single speed belt driven blower, the technician should adjust
the motor pulley size
in residential installations, metal ductwork transmits noise generated by the furnace to the conditioned space, what type of connectors are used to control this?
vibration eliminators
a homeowner complained that his furnace makes a loud bang upon ignition. the technician decides to check the gas pressure and finds 2.2 inches of w.c. at the manifold. the technician should
check gas supply pressure
carbon monoxide is dangerous. what is the maximum level of undiluted CO that is acceptable in a sample of flue gas
400 ppm
the recommended external static pressure on a typical gas furnace bower system is
0.2-0.6
the most common burner used in induced draft furnaces is
inshot burners
ASHRAE standards specify the maximum allowable CO concentration in a living area is
9 ppm
how much current is typically conducted through the flame sensor?
1-10 microamps
a technician starts up a natural gas furnace. the main burner lights and after 60 seconds the blower fan comes on, but the burner flame waver in one corner. the technician suspects
a faulty heat exchanger
when exposed to low concentrations of carbon monoxide, healthy adults may exhibit
headaches and nausea
a furnace that is direct ignition
lights the main burners with an electronic igniter
a mid-efficiency, category I natural gas furnace has a typical air temperature rise of
40-70 degrees
a typical vent stack temperature on a natural gas furnace is
350-450 degrees
a technician starts an intermittent spark ignition furnace. the pilot flame lights, but the spark igniter continues to spark. after 90 seconds, the pilot goes out and the ignition sequence starts again. the technician suspects a faulty
ignition board
a furnace that is designed with the blower motor located above the heat exchanger is called a
downflow
a standing pilot gas valve with 100% shut-off means
gas to the pilot and manifold is shut-off
a furnace that is designed with the blower motor located beneath the heat exchanger is called an
upflow furnace
a customer complains that a 2 year old direct, hot surface ignition furnace will not light. the inducer motor runs, the pressure switch closes, and the igniter begins to glow, but there is no ignition. the furnace locks out while attempting to light. after resetting the furnace, 17 vac is measured a the gas valve and the technician correctly concludes
the gas valve is shorted
the proper instrument for determining the percentage of carbon dioxide in the flue gas of a gas burning furnae is a
combustion analyzer
most thermostats contain on or more sets of contacts to control the heating system of a conditioned space. these contacts are
thermally actuated
a gas furnace has an integrated furnace control (IFC). how is the fan cycled during heat?
timed delay