Natural and Fan-Assisted Draft Appliances - Part A 080205aA

Question 1

Natural draft burners are often called what?

Answer 1

Atmospheric burners

Question 2

What burner do all natural draft appliances use?

Answer 2

Inspirated burner

Question 3

Definition of Primary Air

Answer 3

That portion of the combustion air that is supplied for the initial stages of the combustion process and is supplied upstream from the point of ignition

Question 4

Definition of Secondary Air

Answer 4

That portion of the combustion air that is supplied for the intermediate and final stages of the combustion process and is supplied downstream of the point of ignition

Question 5

Definition of Excess Air

Answer 5

Air supplied to the combustion zone in excess of the quantity of air to assure complete combustion of the fuel but is theoretically not required

Question 6

What type of burner does an atmospheric burner use?

Answer 6

Inspirated

Question 7

The pressure in the Venturi of the burner will be higher or lower than atmospheric pressure?

Answer 7

Lower (below 14.7psi)

Question 8

The quantity of air a burner entrains increase as what increase?

Answer 8

Fuel pressure and velocity

Question 9

Natural draft atmospheric appliances rely on the _____ _____ of the warm air escaping through the combustion chamber vent opening and rising up a chimney to create a ___ pressure area which draws in a new supply of air to the firebox and the effects of ______ creates an air flow into the combustion chamber

Answer 9

stack action, low, buoyancy

Question 10

What are you 3 types of air supply for combustion?

Answer 10

Primary air
Secondary air
Excess air

Question 11

The burner on a hot water tank is an example of what kind of burner?

Answer 11

Upshot Inspirated burner

Question 12

What creates the need for an induced draft fan on an appliance?

Answer 12

Resistance in the heat exchanger (bends and dimpling create more surface area)

Question 13

What are the 2 main burner classifications?

Answer 13

Atmospheric

Power burner

Question 14

What is the main difference between power burners and atmospheric burners?

Answer 14

Power burner is fan assisted

Question 15

A pilot that burns continuously?

Answer 15

Standing pilot (continuous pilot)

Question 16

A pilot which is automatically lit and burns each time there is a call for heat until main burner flame is established

Answer 16

Interrupted pilot (remains lit until burner is lit)

Question 17

A pilot that is automatically lit and burns when the main flame is established and shuts off when main flame is extinguished

Answer 17

Intermittent pilot (lights main burner with call for heat and shuts off when main burner shut off)

Question 18

How is stack action created?

Answer 18

Difference in buoyancy between lighter warm air rising through the appliance venting and heavier cold air flowing into the combustion chamber

Question 19

How does flame lift off occur?

Answer 19

Quantity of primary air is too high for a given quantity of fuel

Fuel pressure is higher than the burner can handle

Fuel moves too quickly through the burner for a given quantity of primary air

Question 20

How is burner flashback created?

Answer 20

Fuel/air mixture moves through the burner ports at a rate slower than combustion burning the fuel

Too low gas pressure

Excessive primary air for a given quantity of fuel

Question 21

How does a yellow flame burner operate and where is it used?

Answer 21

Burns almost entirely with secondary air

Used is some gas fireplaces with simulated logs in firebox

Question 22

What are 2 dangerous compounds that may be created as products of combustion if fuel is not completely burned?

Answer 22

CO (carbon monoxide)

Aldehydes

Question 23

What is the basic difference between an aspirated burner and an Inspirated burner?

Answer 23

Aspirated burners entrain fuel with air

Inspirated burners entrain air with fuel

Question 24

What does the term stack action refer to?

Answer 24

The flow of products of combustion through the appliance and up through the vent

Question 25

What are the products that result from the complete combustion of fuel and air?

Answer 25

CO2 and H2O

Question 26

A 2 stage furnace uses what kind of fan speed?

Answer 26

Staging

Question 27

Appliances with variable firing rates require a burner design with a good turndown ratio. This can be described as what kind of fan speed?

Answer 27

Modulating

Question 28

The burners on a furnace are what kind of burners?

Answer 28

Inshot burners

Question 29

The heat exchanger must not scrub too much heat from the products of combustion for what reason?

Answer 29

There will not be enough heat left for adequate stack action

Question 30

In general, ______ the ______ of fluid flowing through a closed channel ______ the ______ of the channel to the flow of fluid through it

Answer 30

Doubling, volume

Quadruples, resistance

Question 31

How is static pressure created by a centrifugal fan counteracted by discharge housing design?

Answer 31

Increasing the size of the outlet / sudden enlargement

Question 32

The amount of air a natural draft burner entrains increases as what other factor or factors increase?

Answer 32

Fuel pressure and velocity