E5 - self test questions Flashcards
What term refers to the min input of fuel that is required to keep a burner from flaming out?
Low-fire
What term is used to help determine how low a boiler can modulate from max firing rate before it turns off?
Turndown ratio
What type of burner relies upon atmospheric pressure to supply all of its combustion air?
non-mechanical burner
What type of burner uses a fan located downstream of the combustion zone to pull in the air supply for combustion / vent the products of combustion w/ a positive vent pressure?
Induced draft burner
What type of burner uses a mechanical device to supply combustion air at the pressure necessary to only overcome the resistance of the burner?
Fan-assisted burner
What type of mechanical burner relies on the products of combustion to be vented naturally w/ a nonpositive vent stack pressure?
Fan-assisted burner
What type of pre-mix burner has become very common in residential condensing boilers?
Aspirating mixer
What are the limits of Flammability for NG?
4 - 15%
What is the approximate max flame temp for propane, Butane and NG?
1980C
What is the purpose of burner flame retention devices?
Reduce gas mixture velocity
True or False: A luminous flame burner does not premix gas / air before ignition
True
True or False: A bunsen burner produces a large glowing yellow flame
False
A bunsen burner premixes the air w/ the gas before it is ignited
True
Which type of Bunsen flame has a yellowish colour due to the presence of unburned carbon or hydrocarbons
Reducing flame
Which type Bunsen flame has a hissing shortened flame?
Oxidizing flame
True or False: The flow velocity is highest at the centerline of the burner port opening
True
What part of the burner increases the gas velocity / creates a negative pressure used to suck in the combustion air?
Venturi
True or False: The manifold pressure require for an atmospheric burner operating on propane gas is typically 2.5 x higher than that required for natural gas, in order to draw in the higher ratio of primary air required
True
One of the 2 pilot burner categories describes their ability to premix air. What does the other category describe?
Ignition Sequence
If flashback is occurring in an atmospheric burner, which of the following actions may be required?
Decrease the primary air and/or increase the gas pressure.
How can flame lift off be corrected?
Decrease the primary air
What usually causes a noisy, lifting, blowing pilot flame?
High gas pressure
Which of the following conditions would cause a floating flame?
A blocked vent
What could be the problem w/ a furnace if a flame is waving or rolling out when the air circulation fan comes on?
A cracked heat exchanger
There are 2 methods of changing the input to the burner, one is by adjusting the manifold pressure what is the other?
Changing the size of the orifices
The 3 common types of main burner orifices are?
1) Fixed
2) Adjustable
3) Cap
Which type of orifice can commonly be found on dual fuel (propane / NG) appliances?
Cap or universal
How is a residential range w/ universal orifices converted from propane to NG?
Turn the orifice cap counter - clockwise / change the regulator setting
True or False: It is the diameter that is used to calculate the flow rate through an orifice not the area
False
What is the smallest drill size?
3/32”
Which factor does not affect the sizing of the burner orifice?
Position of the burner in relation to the pilot
When using a rotary meter to clock a boiler the LED flow rate screen meter indicates 3.54m cubed / hour of NG. What is the appliance input?
36.64 kW
1000 BTU/ft3
meter pressure = 7” WC
30 sec for test dial to make 1 revolution. What is the appliance input?
60,000BTU/h
True or False: The propane gas orifice sizes are smaller then the required NG orifices for the same appliance.
True
What are the 3 common pilot ignition systems?
1) Continuous
2) Intermittent
3) Interrupted
Which of the pilot ignition system is the pilot flame typically also being used on a heat activated safety device such as a thermocouple?
Continuous pilot
Which of the pilot ignition systems does the pilot flame remain lit throughout the main burner cycle / when the call for heat is satisfied the pilot / main burners are shut off?
Intermittent pilot
Which of the pilot ignition systems is the pilot flame extinguished when the main burner has been ignited?
Interrupted pilot
The point at which the 2 dissimilar metals are joined on a thermocouple is known as what?
Hot junction
Thermocouples are used w/ which type of pilot?
Standing pilot
What portion of the hot junction should be heated by the pilot flame?
First 0.375” - 0.5” thermocouple
What does a thermocouple power when it is being heated?
Safety coil
True or False: A thermopile contains approximately 10 - 30 thermocouples
True
How are multiple thermocouples electrically connected w/ in a thermopile?
Series
What setting should a multimeter be on measuring the flame sensing circuit?
uAmps DC
Flame rods for spark ignition systems are typically made of what high temperature resistant alloy?
Kanthol
What is the primary purpose of a thermocouple?
To prove that the pilot is lit
What is the max time allowed in the event of pilot outage for the thermocouple to cool down / stop the flow of gas to the burner?
90 Seconds
What type of current do thermocouples / thermopiles produce?
DC
True or False: A thermocouple must be under load to perform an open circuit test.
False
What reading should an open circuit test on a thermocouple produce?
30mV
What does a closed - circuit test show?
Millivolt maintained under load
A thermocouple should be replaced if it cannot produce a closed circuit reading of more than…
9 mV
During a pilot-stat coil test at what mV reading should the coil drop out?
Between 5 - 2 mV
