Module 9 Gas Appliances
What activates a flame roll-out switch
A raise in temperature
What is the most common problem associated with aerated pilots
Clogging due to dust or lint
What is multi port burner susceptible to
Clogging with lint from the inside
When is a single acting barometric damper allowed on a propane or natural draft appliance
For an incinerator only
Which type of burner has combustion air supplied by a fan or blower under sufficient pressure to overcome the restriction of the burner and the appliance
Force Draft Burner
Air is supplied to burner under enough pressure to overcome the resistance of the burner and the appliance
Force Draft Power burner
Shuts off the burner in the event that the pressure in a boiler exceed it's desired operating range
High Limit Pressure Switch!
What are the conditions that provide a natural draft venting system with the greatest amount of draft
High stack temperature Low outdoor temperature High stack height
Flame sensing method: Thermocouple
Hot junction is heated by the pilot flame Voltage is generated closing a pilot valve/Switch
Which type of burner has a fan located downstream of the combustion zone
Induced Draft burner
What happens when a fluid is heated
It expands and becomes lighter
How does increasing vent temperature or height affect the draft of a natural draft venting system
It increases the draft
What factor must be considered when installing swimming pool heaters that would not be a concern with a hot-water space-heating boiler?
Low water Temperature
Through which device is fuel discharged to an atmospheric burner
Orifice
You suddenly feel cool when a could covers the sun
Radiation!
How many screws are required at each joint of single wall material
Three
Term for steel or masonry chimney
Type A
Flame sensing method: Bulb and Bellows
-A Bulb filled with fluid senses medium temperature -Bellows that will expand or contract when temperature changes -Expanding Bellows activates a switch to control gas flow to Burner
Explain the term proved pilot
A pilot flame supervised by a flame safeguard control -Detects the pressure of a flame before allowing the main fuel valves to open
What causes the contacts of a steam boiler operating pressure control to open
A rise in steam pressure
Appliance with a fan assisted combustion system
A shut off switch will activate to shut down the burner
What causes the resistance of a thermistor to change
A temperature change
What normally controls the automatic gas valve found on a forced air furance
A thermostat mounted in the space being heated
Where is the blower located on a down-flow furnace
Above the heat exchanger
Describe the functions of a draft hood with respect to Stack effect on the combustion chamber
Negates the effect of the chimney draft to stabilize the combustion process
Turns a boiler or water heater on and off to maintain a desired water temperature
Operating Aqua-Stat!
Describe a constant pilot?
Remains on all the time
Describe a Intermittent pilot
Remains on during the firing cycle
Name two ways in which the burner can be controlled on a unit heater
-A wall mounted thermostat -Manual Switch
What are the two basic types of pilot burners?
-Aerated Pilots -Non aerating pilots
Name the three major ways in which heat is transferred
-Conduction -Convection -Radiation
Describe the functions of a draft hood with respect to Temperature and humidity of the flue products
Dilutes the flue products to reduce the temperature and humidity
Which type of vent draws in combustion air emits flue gases from the same vent
Direct Vent
What device allows dilution air to enter the venting system of an atmospherically fired appliance
Draft hoods
Is the temperature setting of a high-limit aqua-stat higher or lower than the setting of the operating aqua-stat?
Higher
What controls the drying period of a gas fired clothes dryer
Moisture sensor or timer
Which atmospheric burners are the most susceptible to flashback
Mono Port
Which type of atmospheric burner produces a single large flame
Single or mono port burner
Term for single thickness of galvanized or aluminum
Single wall or Type C
Flame sensing method: Constant Supervision
Supervises the flame and must be in constant attendance
Describe the function of the following type B vent components
Supports vent stack Maintains clearance from combustion material
What provides the kinetic energy to entrain the gas required for a premixing inspritor burner
The gas coming out of the orifice into a gas jet mixer
List the components of a typical natural draft venting system
Vent pipe Supports Fire stop spacers Roof Flashing Storm collar Vent Cap
List styles of draft hoods
Vertical Horizontal
In which direction does heat energy flow
Warm to Cold
How will the following appliances react to a block vent
Will spill flue products into the room
Flame sensing method: Thermistor
-Electrical resistance changes in response to temperature -Control responds to resistance which operates a switch to control gas flow to burner
Describe the effect on an appliance with a barometric damper if, The stack draft is increased
-It will raise - Neutral pressure pointed -Lowers the efficiency
Why do designed boiler and water heater manufacturers stamp the distance from the draft hood skirt to the top of the boiler on the draft hood and why is this extremely important
-Prevents Shortening of Flue pipe to accommodate the installed. -The burner neutral pressure point will lower -Excess air will lower to the point of producing carbon Monoxide
Name two types of low water cut-off switches used on gas-fired boilers
-Probe Type -Float Type
What determines the adjustment of a barometric damper
-The type of burner -Combustion chamber - Manufacturer's literature
Describe a Interrupted pilot
-Turns on to light the main flame -Extinguished after the flame has been proved
Flame sensing method: Optical sensors
Allows gas to conduct electricity
Air moving through the burner creates a negative pressure that draws the gas into the burner to be mixed
Aspirator
Shuts off the burners if the vent is totally blocked
Block Vent shut off System!
Fire stop spacer
Block stack effect during a fire and maintains clearances from combustible material
Which type of burner provides complete premixing using mechanical mixers
Blow Mix
Gas is drawn in by the negative pressure created by a blower that is also drawing in air for combustion
Blower Mix
Name two products produced by complete combustion of natural gas or propane
Carbon Dioxide Water Vapour
When you discover a noisy, lifting, blowing flame on a non-aerating pilot,what is the cause of the problem and remedy?
Cause high gas pressure Reduce gas pressure
How do you correct Flame roll-out (Upon ignition)with an atmospheric burner
Check for correct manifold pressure settings and that the proper types of gas controls are used for the appliance
Which type of vent is required when flue gas temperatures exceed 470F
Chimney Type A
How do you correct Yellow tipping with an atmospheric burner
Clean burners thoroughly Adjust primary air opening
Which type of water heating system can be used for both domestic hot water supply and space heating?
Combination Unit
How is the heat transferred form a cooking top burner
Conduction
Heat is felt at one end of an iron bar when the other end is heated
Conduction!
Hot Fluids raise because they are lighter than colder fluids
Convection!
What function other than space heating, do many gas fired rooftop units provide?
Cooling
What helps to keep the flame retained at the burner port of a mono port burner
Crimped ring
Describe the functions of a draft hood with respect to Handling of down draft
Diverts the down-draft away from the combustion chamber to reduce the chances of (Co) production during a down draft condition
List four common types of multi port atmospheric burners
Drilled Port Drilled Pipe Slotted Port Ribbon Port
How do you correct Lifting flame with an atmospheric burner
Reduce primary Air Reduce appliance input rate Only if higher than specified on the appliance rating plate
What are the four functions of a venting system
Removes the flue products to the outdoors Prevents damage from condensation Protects the building from fire hazard Provides air circulation
What three types of gas fired units are used to heat a single room or other small areas?
Room Space Heaters Wall Furnace Baseboard Heater
How is this accomplished
The unit is sealed and a seperate pipe is used for the exhaust and the intake and there are no openings to the interior of the building
How is a piezoelectric voltage generated
Through a mechanical force
Flame sensing method: Bi-metal
Two different metals are bonded Warps in change to temperature Warping activates a switch to gas valve
Term for double wall vent with aluminum inside
Type B
Which type of vent has a double-wall construction with a dead air space between the walls
Type B Vent Type BW vent Type L vent
To what ULC standard must all plastic material used in type BH venting system be approved
U.L.C standard S636
Air drawn into burner by Venting action
Atmospheric Burner
Is used in a forced air furnace and has 2 functions 1 Turns the fan on and off in response to sensing heat in the combustion chamber 2 Shuts down the burner when combustion chamber temperature exceeds a preset value
Combination High Limit/Fan Control Switch!
What is the purpose of an operating aqua-stat
Energize or D-energize the main gas valve in response to the water temperature (180F)
List four common venting problems
Excessive laterals Blockage Excessive change of direction Incorrect or missing vent caps
Air is supplied to burner under enough pressure to overcome resistance of burner only
Fan Assist Burner
What three conditions are regulated in a steam boiler?
Firing of the boiler Steam pressure Feed Water
Shuts down the burners in the event of a failure to vent flue products from the combustion chamber
Flame Roll Out Switch!
How has the use of modern automatic ignition systems affected the time in which a flame failure is detected
Flame failure is detected much faster
What term is used to describe a burner flame that moves back through the burner nozzle
Flashback
Senses the operation of a circulating pump
Flow Switch!
Explain the operation of the following barometric dampers Single Acting
Only swing into regulate the stack draft and closes shut when a double draft is present to prevent soot or ashes from entering
Turns a steam boiler on and off to maintain a desired steam pressure
Operating Pressure Switch!
Direct vent appliance (a) Where does it take it's air from
Outside
Describe 100% Safety
Pilot and Main Burners are shut off if flame is not sensed
Describe a spark ignited pilot
Pilot is lit, or re-lit by a spark
Describe a Hot surface ignition
Pilot or main burner is ignited by hot surface device(Glow Bar)
Natural draft appliance equipped with a spill switch
The spill switch will shut the appliance down and require resetting
How is the heat directed to the floor in a low- intensity infrared heater?
The tubes radiate heat to the reflectors direct the heat to floor
What causes the bi-metal strip to curve with changes in temperature?
The two metals that are joined have different temperature coefficients of expasion
Term for venting system under positive pressure
Type BH
Term for double wall(oval) with aluminum inside
Type BW
Term for double wall vent with stainless steel inside
Type L
What three condition are regulated in a hot water boiler?
Firing of the boiler Aqua-Stat Circulating pump
Describe a Standing Pilot
Pilot remains on all the time regardless of whether sensed or not.
Air and gas are mixed completely before introduction to the chamber by inspiration aspiration or blower mix methods
Pre-mix Burner
Allows hot water or steam to escape form a system if the pressure exceeds a preset maximum value
Pressure Relief Valve!
Senses air movement using a paddle attached to a micro-switch
Pressure Switch
Roof flashing/storm collar
Prevents moisture from entering home
Vent cap
Prevents moisture or foreign object from entering vent system
Explain the operation of the following barometric dampers Double Acting
Swings into regulate the stack draft and also swing s out to relieve a down daft into the room
Allows water to escape if temperature or pressure exceeds a preset value inside a hot water heater
Temperature and Pressure Relief Valve!
State three situations where they are used
When a hazardous atmosphere exists in a building When a building may experience negative pressure When it is not favorable to use a natural draft Vent
Describe the effect on an appliance with a barometric damper if, The stack is decreased
Will lower the neutral pressure point Increase the efficiency to a point (Co) can be produce
Does the furnace fan continue to run if the high-limit switch opens the furnace control circuit?
Yes
Can a chimney with a clay tile liner be lined with a metallic liner system
Yes Some types of applications and situation requires a liner to be installed to prevent condensation
A regulator designed to supply gas at or atmospheric pressure when a vacuum is induced on it
Zero Govenor
What device is used to regulate gas supply to an aspirator type burner
Zero Governor
Describe the undesirable effects of a vent connector coming loose and falling off a gas appliance
Flue products could have (Co) Recirculation of Flue products could cause (Co) Resulting personal injury or death to the building occupants
How do you correct Flame roll-out(Steady) with an atmospheric burner
Heat exchanger blocked or cracked on a forced air furnace if not check appliance input rate
A water temperature sensing device that will shut off the burner if the temperature exceeds the desired operating range of the boiler or water heater
High Limit Aqua-Stat!
Air is drawn in by the vacuum created by the injection of gas to the burner
Inspirator
Shuts the burner off if the water level in a system falls below a desired point
Lower-Water Cut Off Switch!
What are the recommended minimum and maximum port diameters for drilled port atmospheric burners
Maximum No 29 Drill Minimum No 42 Drill
What type of venting system relies on the upward movement of hot gases
Natural draft vent