Module 9 Gas Appliances

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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


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