Siemens JFR Distribution Step Voltage Regulator 21-115532-001 - Manual (Page 19)

SPECIAL FEATURES
Page 15
FORCED AIR COOLING
Certain regulators may be equipped for forced-air cooling and
include fans mounted on the radiators. The fans are usually
automatically controlled by means of the change in oil
temperature (see Connection Diagram). The thermometer
located in the top transformer oil contains two identical
switches which control fan operation when fan control switch is
in “Auto” position.
SUBBASE ASSEMBLY
Subbase assemblies are available in 4-inch high increments
from 21 through 49 inches for most JFR regulators. The
proper height is selected by picking the elevation that will
provide required clearance from foundation to the live part of
the regulator bushing.
The switches are normally set to start the fans at 65°C and to
stop them at 55°C top oil temperature, but may be adjusted
plus or minus 5°C.
A thermal overload relay is mounted on each fan motor. Any
fan that develops trouble will be automatically disconnected
from the line without affecting the other fans of the system.
One fan can be removed from the radiators without affecting
the operation of the others. When fans are out of service,
care must be exercised to prevent overloading the regulator.