High Limit Reset; Access To The Controller Cabinet; Fuses - Parr Instrument 4838 Operating Instructions Manual

Back side
4838 Reactor Controller 230V
Thermocouple burnout protection is included in
each of these controllers. If the thermocouple
should burn out, or if there is a break in the thermo-
couple circuit, power to the heater will be shut off.
In most cases this will cause the controller to show
a "NO CONN" reading. A similar high reading will
be displayed if the controller is turned on without an
attached thermocouple. In either of these situations,
the high limit reset will activate. The thermocouple
break must then be corrected and the High Limit Re-
set must be reset in order to activate the system.

High Limit Reset

Each Series 4838 Controller has a high temperature
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 reheating
the reaction when the temperature falls back below
the limit setting. This must be manually reset before
heating can occur again.
On Model 4838 Controllers the high temperature
limit is preset at the factory to 375 °C for most sys-
tems. On these controllers an alarm condition is
indicated by an illuminated red indicator labeled as
"ALM". If the temperature exceeds the limit, the con-
troller alarm condition will appear, the High Limit
Reset will be tripped, and power to the heater will
be shut off.

Access to the Controller Cabinet

To open the controller cabinet, unplug the power
cord and remove the two screws in the upper
corners of the back panel. Then lift the top plate
upwards, allowing the hinged top and front panel to
swing forward, providing full access to all internal
components.
Caution!
Inside of controller cabinet should be ac-
cessed by qualifi ed personnel only.

Fuses

The 4838 Controller has a number of fuses which
are intended to be fi eld serviceable.
Fuse Rating
Instrument Fast acting, 1
Fuse Amp, 250VAC
Line Fuse(s) Fast acting, 20
Amp, 250VAC
Caution!
Unplug unit before servicing. For continued
protection against possible hazard, replace
fuses with same type and rating of fuse.
4838 Reactor Controller
Part number
139E6
2074E
9