Flames and More
The operating sequence to light the main burners on an intermittent pilot system is
The pilot valve and spark igniter are energized, the pilot flame is proved, and then the main gas valve is energized.
Why should the heating element of a hot-surface igniter NOT be touched when installing a replacement igniter?
The igniter will burn out where you touched it.
The atmospheric pressure and the adjustable spring pressure work together to balance the gas regulator's:
Outlet gas pressure
The operation of modern induced-draft equipment is normally controlled by
An electronic board
The typical start up sequence for a hot surface ignition system is
Combustion blower prepurge, igniter energized after a delay, gas valve energized after a delay, flames sensed, indoor blower energized after time delay.
How long is an ignition trial on a direct spark ignition system?
4 to 21 seconds
Hot-surface igniters are made of
Silicon carbide.
Combination gas valves used on standing pilot furnaces combine:
Pressure regulation, a solenoid valve, and pilot safety.
When the room-temperature setting is reached, what components are opened?
Thermostat and gas valve circuits
Two-stage gas furnaces can use single-stage thermostats that offer:
A timed transition from low to high fire
If pulsed DC current is not present in the flame rod, what is the effect on the gas valve in a direct spark-ignition system?
The valve will remain closed.
Which of the following statements accurately describes silicon carbide?
It is brittle and will break easily.
Why do solenoid-type valves pose a problem for some types of burners?
Solenoids open and close too quickl
In a traditional gas furnace with a standard combination gas valve, what controls the gas valve?
The heating thermostat
Two-stage furnaces require:
2 stage gas valve
What type of flame proving do direct spark ignition controls use?
Flame rectification
Hot-surface igniters typically operate on ____ voltage
120V
Some furnaces use two automatic shutoffs that are mechanically in series to provide additional safety. What type of valves are these?
Redundant valves
What does the furnace board do on most modern furnaces?
It controls the ignition, safety, and blower operation.
Modulating thermostats have both ________ control
proportional and integral
How does the flame rod sense the flames in a flame rectification circuit
The flame changes the AC voltage to pulsed DC current
Hot-surface igniters typically operate for a _________________ per day
few minutes
Why do direct spark ignition furnaces and hot-surface ignition furnaces require redundant gas valves?
For safety since there is no pilot safety solenoid
The major electrical loads in an induced-draft hot surface ignition furnace are
Induced-draft blower, indoor fan motor, the gas valve, the igniter.
Modulating furnaces often have a pressure transducer to measure the
Draft pressure.