MIL-DTL-16036M(SH)
3.5.7 Side sheets. Ends of each standardized unit or special section shall be enclosed by solid sheets, at least
1/16 inch thick, welded to the switchboard framework, except where the arrangement of switchgear within the
section is such as to require side access for maintenance, in which case the side sheet or a portion thereof shall be
removable. Removable side sheets are not considered structural members. The side sheets shall be welded by
intermittent welds, spot welds, or plug welds to the vertical and horizontal frame members. The gusset plates in the
plane of the sheet may be omitted, provided the sheet is welded to the frame at the corners with the same length of
welding that would normally be employed with a gusset plate. When gusset plates are omitted, plug welding shall
be used only on the side sheets at the top corners of the frame. Side sheets shall be cut to provide for
interconnecting bus bars and wiring, and insulating spacers shall be employed to close the openings. Location of
3.5.8 Compartmentation. Each unit shall be internally subdivided by barriers of either sheet metal,
nonconductive material, or a combination of both to form separate compartments for the circuit breakers to isolate
them from the bus work and cable connections and eliminate gaps between compartments. There shall be no gap
between the barrier and top enclosure of the switchboard. The gap between the barrier and the horizontal plane at
the bottom of the switchboard shall not exceed 3/8 inch. Gaps on any switchboard barrier sections not covered
above shall not exceed 1/16 inch. If necessary, barriers may overlap. The ACB stationary component is acceptable
as a rear barrier in an ACB compartment. The ACB stationary component (cradle) may have vents present in their
design. Cradle vents do not invalidate the compartmentation requirement. For spraytight units, the barriers shall be
perforated with 1/4-inch holes to allow for vertical flow of air. When barriers are installed, insulation distances shall
be as specified in 3.6.2. A separate compartment shall be provided for each Type ACB circuit breaker, but all Type
AQB circuit breakers on one unit may be in a common compartment. The compartments shall be constructed to
prevent an arc or fault from spreading from one compartment to another or into the area occupied by the bus work.
Bus disconnecting devices shall be located outside the circuit breaker compartment. Each Type ACB circuit breaker
compartment shall be enclosed on the front by a removable panel section. On Type AQB circuit breaker
compartments over 60 inches high, the front enclosure shall be made by two panels.
3.5.8.1 Compartmentation for switchgear equipped with arc fault detectors. Compartmentation for switchgear
which utilizes Arc Fault Detection (AFD) shall be similar to that of 3.5.8 with the exception that the gap between the
unit s internal subdivision barrier and the horizontal plane at the bottom of the switchboard shall not exceed 3/4
inch. All other gaps shall not exceed 3/16 inch.
3.5.9 Ventilation. Ventilation for compartments within a unit and for the unit itself shall be constructed, and
the openings sized, so that the maximum internal temperature shall not exceed 167 °F (75 °C) when the unit is
operated in an external ambient temperature of 122 °F (50 °C). Type ACB circuit breakers shall be vented through
the front of the unit or through the rear of the unit. Components and wiring required to be installed in the units shall
operate to rated capacity in the above internal, ambient temperature without performance degradation. Ventilating
louvers and grill openings shall minimize the probability of entrance of solids and shall protect personnel against
injury from electric arcs. An operating test of applicable controls and communication functions shall be performed
at temperature stabilization to verify functionality at high temperatures.
3.5.9.1 Spray baffles. When spraytight units are specified, louvered or other type of ventilation openings shall
have spray baffles to meet the requirements of 3.17.4, and these baffles shall be in accordance with figure 12 or an
equivalent that meets the spraytight and thermal testing requirements (see 4.4.3.6).
3.5.9.2 Fans. Thermostatic fans may be added to the switchboard. When specified (see 6.2), fans shall meet
the following requirements:
a.
Fans shall activate only when the internal ambient temperature in a compartment exceeds 140 °F (60 °C).
b.
Easily accessible, washable air filters shall be provided for intake fans.
c.
Fans shall be disabled by operation of an appropriate maintenance switch.
d. When fans are installed, airborne and structureborne noise testing in accordance with MIL-STD-1474,
Equipment Grade E and MIL-STD-740-2, Type IV shall be included in the first article test.
e.
Fans shall be activated during selected first article tests as specified herein.
25
For Parts Inquires submit RFQ to Parts Hangar, Inc.
© Copyright 2015 Integrated Publishing, Inc.
A Service Disabled Veteran Owned Small Business