MIL-PRF-22594C(SH)
4.5.5.1 Kilowatt rating tests. The kilowatt rating of each size and type heater shall be determined at ambient
temperature and corrected for the conditions specified in 3.12 and 3.12.3. The temperature rise through the heaters
shall be as specified in table I, and the tolerances for airflow and ĆT shall be in accordance with 3.12. The kilowatt
rating shall be as specified in 3.12.3. The test shall be conducted in accordance with ASHRAE STD 33, except as
follows:
a.
The type of heating shall be electric and the power source shall be 115 volts ±5 percent, three-phase,
60-Hertz for heater Sizes 19EH through 22EH (Type L), and 440 volts ±5 percent, three-phase,
60-Hertz for heater Sizes 22EH (Types M and H) through 38EH.
b.
Readings of line volts, amperes, and watts input shall be recorded. Heater shall be operated for at least
30 minutes before commencing test.
c.
Use: 3412 British thermal units per hour (Btu/h) = 1 kilowatt.
4.5.5.2 Airflow resistance. The resistance to airflow of the heater shall be determined in accordance with
ASHRAE STD 33 at rated airflow ±5 percent at standard conditions as described in 3.11.1. The resistance to
airflow shall not exceed that specified in 3.12.4.
4.5.5.3 Over-temperature protection. Heater shall be operated at rated airflow and voltage for at least
30 minutes with an entering air temperature of at least 70 °F. The fan providing the air supply shall be shut off and
the surface temperature of the heating elements measured at five points selected at random. The mean measured
surface temperature at which the high limit cutout switch contacts open shall not exceed 750 °F.
4.5.5.4 Circuit strength test. Heater electrical circuits shall be subjected to and shall withstand for a period of
1 minute, a dielectric test voltage of twice the rated line voltage plus 1,000 volts applied between each electrical
conductor circuit and the frame with all other electrical conductor and metal parts grounded. The voltage wave shall
be in accordance with 3.12.5.1.
4.5.5.5 Insulation resistance test. Insulation resistance of the heater assembly at the normal operating sheath
temperature shall be measured within 60 seconds after the heater has been deenergized after being energized for at
least 10 minutes or elements have reached a temperature of 450 ºF, to determine conformance with 3.12.5.2.
4.5.5.6 Creepage and clearance. Heater shall have the creepage and clearance distances measured to determine
whether the distances are in accordance with 3.12.6. Any heater where there is evidence that the creepage or
clearance distances, when measured, are not in accordance with 3.12.6 shall be grounds for rejection.
4.5.6 Permeability tests. A permeability test of nonmagnetic material used in construction of the heater
assembly shall be conducted in accordance with MIL-STD-2142, Test 501.
4.5.7 Maintainability demonstration. The heater shall be examined after testing, and the capability to maintain,
disassemble, and repair the unit shall be demonstrated. The demonstration shall be conducted utilizing commonly
available tools and with other-than-expert mechanics. The maintainability demonstration shall include, but not be
limited to, the following:
a.
Wiring, terminals, and electrical connections are accessible for servicing and testing by removing
terminal enclosure cover but without requiring the removal of a subassembly or complete heater
casing.
b.
Heating elements are replaceable without removing the adjoining ductwork.
c.
Fins of the heating elements may be cleaned with a nonmetallic stiff bristle brush without being
damaged.
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