Induced Burners and Combustion - Part A 080205bA Flashcards
Return air lower limitation?
55°F - 80°F
What name is given to a furnace that can be installed in different positions? (horizontal/vertical)
Multi-poise
What describes a well functioning burner flame?
Stable, relatively quiet, soft blue without curling, floating or liftoff and the flames must not impinge on the sides of the heat exchanger
What would be an indication of dirt or dust in the burner tubes?
Orange flame
What would a burner flame that is yellow in appearance indicate?
Insufficient primary air or too much fuel
Where are controls that sense water temperature placed in?
Thermal wells
What must happen for a open tube induced draft burner to function properly?
Fuel must be discharged into the centre of the burner throat from the discharge orifice
How does a open tube induced draft burner entrain primary air for combustion?
The venturi design of thr burner entrains primary air through a NON-adjustable air opening
What are some of the advantages of an open tube induced draft burner?
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
What type of burner does not rely on venturi action to entrain primary air?
Ported tube burner
What are some of the characteristics of a ported tube burner?
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
How does a ported tube burner entrain its primary air?
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
Induced burners can be found in what 2 configurations?
Open port burner or ported tube burner
What type of burner is constructed similar to natural draft burners?
Open tube burner
What is another reason for the wide use of the open tube burner?
Many of the forced air appliances it is applied to can be placed in multiple orientations
Other styles of burner other than open tube are used for induced draft appliances but what condition must be carefully addressed?
Over-fire draft (especially with modulated operation)
What is over-fire draft and what can occur because of it?
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
Where would you usually find a ported tube burner?
Induced draft boilers
Induced draft boilers are often made of stainless steel for what reason?
Resist corrosion and the high heat of the combustion chamber
Why must an induced draft fan be properly sized?
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
What is another term for complete combustion?
Perfect combustion
What are the theoretical perfect combustion ratios for natural gas and propane gas?
Nat. Gas = 10/1
Propane= 24/1
What can cause the cooling of a burner flame?
Flame impinging on the surface of the heat exchanger
What would a green burner flame indicate?
Air conditioning refrigeration leak
What would a red burner flame indicate?
Chemical contamination of the combustion air supply
A burner that only has secondary air avaiable would have what characterisitics?
Flames with pronounced yellow tips
