Burnham 4FHL-63A Installation And Operating Instructions Manual page 10

Duct size, if used, shall have a minimal cross
sectional area equal to the opening size.
Outside air openings may be protected by mesh,
grills, or louvers. When doing so, the free area sizing
must be compensated for the blocking effect of such
obstructions. Protective mesh must be no smaller
than 1/4". If the free area of the grilles and louvers
is unknown, use 20-25% free area for wood louvers,
and use 60-75% free area for metal louvers and
grilles.
Closeable louvers must be electrically interlocked
with the burner to prevent the burner from firing if the
louvers fail to open or remain open.
The boiler room should not be under negative
pressure at any time.
Adjustment to air opening and duct size shall be
made to boilers at higher altitude installations (above
1,000 ft). An adjustment of 3.5% per 1,000 ft of
elevation is recommended.
6. LOCATION OF ASME STAMPING DATA
The ASME stamping data is located as follows:
1. Series 4FH: Sizes 63 thru 675, on the left side of
the boiler shell near the front, under a 3 x 6 cover
plate. Sizes 827 thru 3075, on the right side front
tubesheet.
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7. NORMAL BOILER WATER LEVEL
The normal boiler water level is the water height
where the steam boiler water level should operate at. If
using an on/off pump control, this will correspond with
the "pump-off" level. The following dimensions represent
the vertical distance from the reference point to the
Normal Water Level.
Series 4FH Firebox – Reference point is from the top of
the boiler base
4FHL-63A/107A
4FHL-127A/209A
4FHL-240A/345A
4FHL-360A/450A
4FHL-563A/675A
4FHL-827/993
4FHL-1157/1323
4FHL-1654
4FHL-1985/2645
4FHL-3075A
40-3/4"
48-1/2"
55"
66-3/16"
69"
74"
85-1/2"
100-1/4"
114-1/4"
122-1/2"