8
Protective Fuses and Relays
4848T Reactor Controller (230V), Back Side
An instrument fuse is mounted on the back panel.
This is a Fast-acting, 250VAC, 2.0 amp fuse, intend-
ed to protect the temperature control module and
any installed display modules.
The motor reset/motor fuse provides overload
protection for 0-90VDC motors. This is a re-settable
breaker designed to protect the motor if it becomes
overloaded. The breaker will have a rating selected
to match the motor on the apparatus.
A lighted fuse holder provides protection for 0-180
VDC motors. A light will come on if the motor
becomes overloaded and the fuse burns out. The
fuse rating will be selected to match the motor on
the apparatus.
A load fuse is mounted on the back panel on 115V
systems. This fast-acting, 250VAC, 20 amp fuse
is intended to protect the controller and prevent
electric shock hazard from fault from occurring.
Two load fuses are mounted on the back panel on
230V systems. These are fast-acting, 20 Amps, 250VAC
and are intended to protect the controller and to pre-
vent electric shock hazard from fault from occurring.
The 4848T Controller has a number of fuses which
are intended to be field serviceable. See the Parts
List Section on page 23 for more information.
CAUTION! Unplug unit before servicing.
For continued protection against
possible hazard, replace fuses with same
type and rating of fuse.
Thermocouple burnout protection is included in
each of these controllers. If the thermocouple
should burn out, or if there is a break in the ther-
mocouple circuit, the apparent temperature will
rise to the top of the sensor limit, triggering a
sensor break alarm.
High Limit Reset
Each Series 4848T Controller has a high tempera-
ture limit control which will trip the High Limit
Relay and shut off the heater if the temperature
reaches a preset level. If tripped, the lockout relay
will pop out, thereby preventing the system from
heating the reaction when the temperature falls
back below the limit setting. This must be manually
reset before heating can occur again.
On Model 4848T Controllers the high temperature
limit is preset at the factory to 375 °C for most
systems. If the temperature exceeds the limit, the
controller alarm condition will appear.
Motor Speed Control
4848T Controllers are equipped with a solid
state speed control module for use with the variable
speed, DC motors installed on stirred reactors.
The module itself (approximately 4 inches square) is
mounted inside the chassis on the bottom plate. A
motor switch and a speed adjustment potentiometer
are mounted on the front panel. Each module also
requires a resistor matched to the horsepower of
the motor with which it will be used, as listed in the
following table:
Motor
Rating
Motor
Voltage
Resistor
Required
Part
Number
1/17 HP 90 VDC 0.25 ohm 876E6
1/8 HP 90 VDC 0.10 ohm 876E3
1/4 HP 90 VDC 0.05 ohm 876E
1/4 HP 180 VDC 0.10 ohm 876E3
1/2 HP 90 VDC 0.025 ohm 876E2
1/2 HP 180 VDC 0.05 ohm 876E
3/4 HP 180 VDC 0.035 ohm 876E5
4848T Controllers furnished as a part of a complete
stirred reactor system will have the proper
resistor installed at the factory. Any controller sold
separately will require a motor specification so that
the proper resistor may be provided.
COMPONENT SUMMARY (Continued)
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