Midco Unipower G-Series - Manual (Page 4)

■ ■ The top of the combustion chamber should be positioned 2" to 6" above the base of the heat
exchanger. If the combustion chamber is to be set directly on the floor, provide a minimum of 1 / 2 "
insulating millboard or magnesia block underlay for floor protection. Use high temperature fill such as
vermiculite in voids around the combustion chamber. Any portion of the heat exchanger not exposed to
circulating air of water should be covered with insulating firebrick.
■ ■ The combustion chamber sizes given in Table 1 are based on the maximum rated burner capacity. If
the input is to be permanently set at a reduced rate the combustion chamber floor area can be reduced
proportionately to the proposed input, with the length as closely proportioned to twice the width as
p o s s i b l e .
■ ■ Where recommended size combustion chambers (225,000 BTU/sq. ft.) can be accommodated, the
type of construction shown in Figure 1 should be used. If lack of space prohibits use of this construction,
higher BTU values per square foot can be allowed for by using the constructions shown in Figures 2 and
3 .
■ ■ The back wall of the combustion chamber should be carried 2 or 3 courses higher and overhung to
deflect the flames from direct impingement on the rear heat exchanger surface. Hard firebrick should be
used to prevent erosion of the brick by high velocity gases.
■ ■ The burner is equipped with a mounting flange for direct attachment to the boiler front, and
mounting brackets for legs. Use both if necessary for rigid installation. The burner nozzle must not
extend into the combustion chamber. It should be sealed into the opening as shown in Figure 4.
WARNING: Burner cabinet must be mounted in orientation in Figures 4 and 7. Any other
mountings may cause a dangerous condition, and will void burner warranty and agency
approvals. Non-standard arrangements may be available for some models. Consult factory for
details if required.
■ ■ The refractory lined combustion chamber can be omitted in "Scotch Marine" and "Steam
Generator" boilers or warm air furnaces that do not include ashpits.The burner is fired directly into the
heat exchanger, requiring no refractory unless the combustion chamber is so short that flame would
impinge excessively on the rear heat exchanger wall (this is particularly important in a warm air furnace).
Refractory protection is recommended if the length of the primary chamber is less than 20% larger than
the length given in Table 1. In
any case, the burner entry wall
must be refractory lined if it is
not a heat exchanger surface.
Firing Door Installations
■ ■ It is advantageous, on
occasion, to fire through the
boiler firing door. For example,
pitting can be avoided on low
base boilers, damage to the
burner can be avoided if
basement flooding is prevalent
or the combustion chamber
volume can be reduced in
boilers with unusually large
a s h p i t s .
■ ■ Great care in planning will be
required for firing door applications since flame impingement on boiler surfaces is more probable. Do
not fire a boiler containing a drop section directly in the path of the flame, or over the water grate in a
smokeless type boiler. The firebox length must be great enough to exceed the combustion chamber
lengths given in Table 1 by at least 20%.
III Combustion Chamber
Continued
Figure 4: Construction at Burner Entrance
Figure 3: Typical Floor and Wall Construction
For 350,000 BTU Per Square Foot (Maximum)