Induced Burners and Combustion - Part A 080205bA

Question 1

Return air lower limitation?

Answer 1

55°F - 80°F

Question 2

What name is given to a furnace that can be installed in different positions? (horizontal/vertical)

Answer 2

Multi-poise

Question 3

What describes a well functioning burner flame?

Answer 3

Stable, relatively quiet, soft blue without curling, floating or liftoff and the flames must not impinge on the sides of the heat exchanger

Question 4

What would be an indication of dirt or dust in the burner tubes?

Answer 4

Orange flame

Question 5

What would a burner flame that is yellow in appearance indicate?

Answer 5

Insufficient primary air or too much fuel

Question 6

Where are controls that sense water temperature placed in?

Answer 6

Thermal wells

Question 7

What must happen for a open tube induced draft burner to function properly?

Answer 7

Fuel must be discharged into the centre of the burner throat from the discharge orifice

Question 8

How does a open tube induced draft burner entrain primary air for combustion?

Answer 8

The venturi design of thr burner entrains primary air through a NON-adjustable air opening

Question 9

What are some of the advantages of an open tube induced draft burner?

Answer 9

The burner has low flow restriction, good turn down characteristics, and easily responds to variable rates of air and fuel during modulation, allowing it to be used at multiple firing rates

Question 10

What type of burner does not rely on venturi action to entrain primary air?

Answer 10

Ported tube burner

Question 11

What are some of the characteristics of a ported tube burner?

Answer 11

Made of thin walled straight stainless steel tube. Relies on good control of the air draft over the fire by an induced draft fan pulling primary air through a non-adjustable air inlet to provide steady and stable burner flames during operation

Question 12

How does a ported tube burner entrain its primary air?

Answer 12

The burner does not rely on venturi action to entrain primary air but on the jet of fuel escaping from the orifice and the vaccum created by the induced draft fan to pull the primary air into the burner through a non-adjustable air inlet

Question 13

Induced burners can be found in what 2 configurations?

Answer 13

Open port burner or ported tube burner

Question 14

What type of burner is constructed similar to natural draft burners?

Answer 14

Open tube burner

Question 15

What is another reason for the wide use of the open tube burner?

Answer 15

Many of the forced air appliances it is applied to can be placed in multiple orientations

Question 16

Other styles of burner other than open tube are used for induced draft appliances but what condition must be carefully addressed?

Answer 16

Over-fire draft (especially with modulated operation)

Question 17

What is over-fire draft and what can occur because of it?

Answer 17

If too much air flows over the burner while it operates, over-fire draft can be created which can cause flame lift off from the burner

Question 18

Where would you usually find a ported tube burner?

Answer 18

Induced draft boilers

Question 19

Induced draft boilers are often made of stainless steel for what reason?

Answer 19

Resist corrosion and the high heat of the combustion chamber

Question 20

Why must an induced draft fan be properly sized?

Answer 20

The quantity of air and combustion gases it has to remove must be carefully calculated to prevent the development of excessive over fire negative pressure and/or positive pressure in the venting system

Question 21

What is another term for complete combustion?

Answer 21

Perfect combustion

Question 22

What are the theoretical perfect combustion ratios for natural gas and propane gas?

Answer 22

Nat. Gas = 10/1

Propane= 24/1

Question 23

What can cause the cooling of a burner flame?

Answer 23

Flame impinging on the surface of the heat exchanger

Question 24

What would a green burner flame indicate?

Answer 24

Air conditioning refrigeration leak

Question 25

What would a red burner flame indicate?

Answer 25

Chemical contamination of the combustion air supply

Question 26

A burner that only has secondary air avaiable would have what characterisitics?

Answer 26

Flames with pronounced yellow tips