Installation guide

ManualsBrandsBeckett ManualsBurnerAFG

and the oil has not been heated up to maximum

temperatureat this point. (SeeFigure 19.)

Modern flame retention burners are not as

dependent on chamber shape.

A well designed chamberwill confine the flame,

and more reflected heat will enter the combustion

process in its early stages. Thiswill aidcombus-

tionandprovide much smootherignition.In

makingalterationsinthe chamber,you must keep

in mind thatyou must use the nozzlespraypattern

andangleto fit the chamberas recommendedby

manufacturer'sspecifications.

Walls. It is important that the walls of the

chamber be high enough to assist combustion, but

not so high as to interferewith the heat transfer

from the combustionproducts to the heat

exchanger.Figure 22 shows the height tobe used

based on the firing rate. The chamber wall should

be 2 to 2-1/4 times as high above the nozzle as it

isfrom the floor to the nozzle.

If the base of a heating unit has a tendency to

overheat, the walls should be 2-1/2 to 3 times the

height from floor to nozzle. This is sometimes a

problem in gravity type air duct systems or

boilers that have been converted from coal to oil.

Be sure to use insulation between the furnace and

chamber wall up to the top of the wall.

Space between the chamber wall and the heating

plant should be filled with an insulating material,

such as mica pellets--except in wet leg or wet

base boilers. Poor grade of backfill shortens

the life of the chamber, reduces the efficiency

at which the oil burns, and increases

combustion noise.

Burner Setting. The chamber must be installed

so that the oil can burn cleanly without impinging

on the floor and causing carbon to form. Figure

23 shows recommended inside dimensions. The

burner end cone should be installed 1/4" back

from the inside chamber wall. We recommend

that you install refractory fiber material around

the outside diameter of the burner end cone and

air tube. If insulating material is not available,

and chamber opening exceeds 4-3/8", burner end

cone set back must be increased. (See Figure 20.)

Soft Fiber Refractory. Refractories of low

specific heat and low conductivity (insulating)

will rise in temperature more rapidly from a cold

start and maintain a higher temperature during

steady operation of an oil burner. This will help

produce more complete combustion and increase

the heat transfer by radiation to the heat transfer

surfaces of the heat exchanger.

Tests by the National Bureau of Standards

comparing a hard brick chamber to a precast soft

chamber in the same boiler determined that

losses by radiation, conduction, convection and

incomplete combustion were 13.4% for the brick

and 8.6% for the precast. The difference was

equal to 8300 Btu's per hour in favor of the

precast. This amounts to a possible saving of 6%.

Another advantage of soft fiber refractories is the

fact that they cool down faster than hard refracto-

ries. This helps prevent nozzle overheating and

afterdrip. Also---since soft refractories store less

heat--off cycle heat loss is reduced. Examples of

soft refractory chambers are shown in Figure 21.

Many modern residential boilers have no

chamber, but often a target wall and/or a blanket

on the floor.

"A" = Usable air tube length.

Face

of Firebox

FIGURE 20 Air tube insertion

The burner headshould be 1/4"back from the inside

wall of the combustion chamber. Underno circum-

stances should the burner headextend into the

combustion chamber. If chamber opening is in excess

of 4 3/8", additional set back may be required.