CSR-20 & CSR-40, September 1999
Safety Precautions
General Safety Precautions for Servicing Controllers
xi
General Safety Precautions for Servicing
Units (or Containers) Equipped with a
Microprocessor Controller
Precautions must be taken to prevent electrostatic discharge
when servicing the
µ
P-D microprocessor, output module and
related components. If these precautionary measures are not
followed, the risk of significant damage to the electronic com-
ponents of the unit is possible.
The primary risk potential results from the failure to wear
adequate electrostatic discharge preventive equipment when
handling and servicing the microprocessor. The second cause
results from electric welding on the unit and container chassis
without taking precautionary steps.
Controller Repair
When servicing the microprocessor, it is necessary to ensure
that electrostatic discharges are avoided. Potential differences
considerably lower than those which produce a small spark
from a finger to a door knob can severely damage or destroy
solid-state integrated circuit components. The following pro-
cedures must be rigidly adhered to when servicing these units
to avoid microprocessor damage or destruction.
1.
Disconnect all power to the unit.
2.
Avoid wearing clothing that generates static electricity
(wool, nylon, polyester, etc.).
3.
Do wear a static discharge wrist strap (TK P/N 204-622)
with the lead end connected to the microprocessor’s
ground terminal. These straps are available at most elec-
tronic equipment distributors. DO NOT wear these straps
with power applied to the unit.
4.
Avoid contacting the electronic components on the circuit
boards of the unit being serviced.
5.
Leave the circuit boards in their static proof packing mate-
rials until ready for installation.
6.
If a defective microprocessor is to be returned for repair, it
should be returned in the same static protective packing
materials from which the replacement component was
removed.
7.
After servicing the circuit board and any other circuits, the
wiring should be checked for possible errors before restor-
ing power.
Welding of Units or Containers
Whenever electric welding is to be performed on any portion
of the refrigeration unit, container or container chassis with the
refrigeration unit attached, it is necessary to ensure that weld-
ing currents are NOT allowed to flow through the electronic
circuits of the unit. These procedures must be rigidly adhered
to when servicing these units to avoid damage or destruction.
1.
Disconnect all power to the refrigeration unit.
2.
Disconnect all quick-disconnect wire harnesses from the
back of the
µ
P-D controller. Also disconnect the wire
harness from the Output module.
3.
If the unit is equipped with a Remote Monitor Module
(RMM) or Integrated Remote Monitor Unit (IRMU), dis-
connect all wire harnesses from the RMM/IRMU circuit
board.
4.
Switch all of the electrical circuit breakers in the control
box to the OFF position.
5.
Weld unit and/or container per normal welding proce-
dures. Keep ground return electrode as close to the area to
be welded as practical. This will reduce the likelihood of
stray welding currents passing through any electrical or
electronic circuits.
6.
When the welding operation is completed, the unit power
cables, wire harnesses and circuit breakers must be
restored to their normal condition.
