Combustion Ignition and controls Flashcards
Why are Combustion/Ignition controls designed to react quickly?
To prevent an accumulation of unburned fuel in a combustion chamber
Which of the following would be considered an operating control?
Thermostat
limit switch
fan control
fuel control valve
a and b
Thermostat
Older combustion safety control systems utilize flame rectification systems.
T or F
F
The voltage produced by a thermo-electric device is dependent upon;
The temperature difference between the hot & cold junction
Flame rectification relies on flame;
Conductivity
The only portion of the ac signal that conducts current during rectification is the swing.
positive
For flame rectification to be effective the surface area of the ground conductor must be a minimum ratio larger than the flame rod.
4:1
Flame rectification systems operate the best when the surface area of the ground conductor is a ratio larger than the flame rod.
10:1
The flame scanner that detects light wavelengths that are able to be seen by the human eye is/are?
UV
visual
IR
B and C
Visual
The flame scanner that detects light wavelengths that are located in the last 1/3 of the flame envelope is/are?
uv
visual
IR
A and C
IR
Hot surfaces found in a firebox after the burner has been extinguished can be a problem for which type of visual flame scanner?
Uv
visual
IR
ALL
IR
Safety controls used on burners over 400 MBH are typically of the reset type.
manual
What burner ignition device avoids wasting fuel for pilot flames and assemblies?
Direct spark igniter and Hot surface igniter
Older hot surface ignitors were constructed of;
silicon Carbide
A spark igniter must be driven by sufficient power that will jump an air gap of to its receiving electrode.
1/8”
Hot surface igniters are most susceptible to damage;
During transportation
Pilot flames are generally considered to be;
Non-aerated
Hot surface igniters may be either 24 volts or 120 volts.
T or F
True
Manufacturers suggest a spark ignition system are able to be modified for field alterations.
False
A pilot flame must be capable of rapid burner ignition when the flame is _____________.
at its smallest size
Which test is required on all pilot operated burners?
Turn-down test
The acronym “ECO” represents;
energy cut off
The ________________________ allows an ECO to replace the temperature relief portion of a temperature and pressure relief valve on a hot water storage tank.
National Plumbing Code of Canada
The power unit in the fuel control valve must respond to flame failure within ___________ for continuous pilot operated systems installed on gas fired furnaces 400 MBH or less.
180 secs
The power unit in the fuel control valve must respond to flame failure within ____________ for direct-spark or hot surface ignition systems installed on gas fired furnaces 400 MBH or less.
90 secs
Ignition and flame proving components position is/are determined by the;
Manufacturer
Placement of the flame rod is so that approximately one inch (25 mm) of the flame rod tip is enveloped in the outer cone of the burner flame with the rod placed at the of a bank of burners, away from the primary ignition device.
far end
Oxide buildup can be removed from a flame rod by gently cleaning it with;
scotchbtite pad OR fine emery cloth
If an igniter requires replacement, you should try to obtain the replacement part.
original equipment
What term is used to describe ignition of several burners in sequence as the flame travels from one burner to the next when utilizing a hot surface igniter to light the main burners?
Crossover
Before you attempt any repair or trouble-shooting on a gas-fire appliance you should familiarize yourself with;
Manufacturers instructions AND sequence of operations
With regards to the normal operating sequence of a HSI mid-efficient furnace, what would be the next occurrence after the air-proving switch has been activated?
Energize the hot surface igniter
With regards to the normal operating sequence of a mid-efficient furnace, what should occur after the main burner fuel has been ignited?
Prove the flame THEN de-emergize the igniter
With regards to the normal operating sequence of a mid-efficient furnace, what portion of the sequence timing can typically be altered?
circulating air fan delay
If a heat demand is disrupted due to a main burner flame not igniting and the control tries for ignition for a second or third time, the control could be described as;
Recycling
If a heat demand is disrupted due to a loss of flame signal during normal operation and the control immediately tries to re-light the burner, the control could be described as;
Retrying
If a heat demand is disrupted due to a loss of flame signal during normal operation and the control immediately locks out, the control could be described as;
Non-retrying
Furnaces are fabricated to the requirements set out in the current;
CAN/CSA 2.3
When you consider code requirements for operating controls of gas appliances, there are basic set/s of documents.
3
