MIL-PRF-24775A(SH)
Nozzle air temperature (°F)
h.
Nozzle area (ft2)
i.
j.
Heater kilowatts (kW)
k.
Heater voltage (V)
l.
Fan motor wattage (W)
m. Fan speed (r/min)
n.
Fan motor voltage (V)
o.
Fan motor amperage (A)
p.
Humidity ratio, pound (lb)
q.
Humidity ratio at nozzle (lb)
r.
Airflow rate (lb/min)
Airflow rate (ft3/min)
s.
t.
Specific gravity
Density (lb/ft3)
u.
v.
Ext. S.P. (in. w.g.)
w. Total air side capacity (Btu/h)
x.
Net air side capacity (Btu/h)
y.
Heater capacity (Btu/h)
z.
Average heating capacity (Btu/h)
aa. Average kW (kW)
bb. Heat balance (percent)
cc. Motor horsepower (hp)
4.5.2.9 Over-temperature protection. Heater shall be operated at rated airflow and voltage for 30 minutes with
an entering air temperature of 70 °F. The fan providing the air supply shall be shut off and the surface temperature
of the heating element measured. The high limit surface temperature, at which the contacts of the over-temperature
switch open, shall be not greater than 750 °F. If the surface temperature does not exceed 750 °F, the temperature at
which the contacts open shall be taken.
4.5.2.10 Dielectric strength. The heater elements shall be subjected to a high potential voltage of 1880 volts, at
a frequency of 60 Hz between each element and the frame, with all other electric circuits and the metal parts
grounded. Each element shall withstand the above voltage for at least 1 minute. The test shall be conducted with
the main electrical power disconnected and the heater at ambient room temperature.
4.5.2.11 Heater element tests. The following tests shall be performed by the manufacturer on the heater
elements:
a.
Insulation resistance tests 3.12.5.2.
b.
Dielectric strength tests 3.12.5.3.
c.
Moisture resistance tests 3.12.5.4.
d.
e.
Creepage and clearance tests 3.12.5.6.
4.5.2.11.1 Accelerated life test. Accelerated life test by fusion shall be conducted as follows:
a.
Support element in still air.
b.
Apply rated voltage and wattage.
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