Thermo King 098203, Maintenance Manual

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Safety Instructions
11
Low Voltage
Control circuits are low voltage (24 Vac and 12 Vdc). This voltage potential is not considered dangerous.
Large amount of current available (over 30 amperes) can cause severe burns if shorted to ground. Do not
wear jewelry, watch or rings. These items can shortcut electrical circuits and cause severe burns to the
wearer.
Electrostatic Discharge Precautions
Precautions must be taken to prevent electrostatic discharge while servicing the MP-3000a
microprocessor and related components. The risk of significant damage to the electronic components of
the unit is possible if these precautionary measures are not followed. The primary risk potential results
from the failure to wear adequate electrostatic discharge preventive equipment when handling and
servicing the controller. The second cause results from electric welding on the unit and container chassis
without taking precautionary steps.
Electrostatic Discharge and the Controller
You must avoid electrostatic discharges when servicing the controller. Solid-state integrated circuit
components can be severely damaged or destroyed with less than a small spark from a finger to metal
object. You must rigidly adhere to the following statements when servicing these units. This will avoid
controller damage or destruction.
• Disconnect all power to the unit.
• Avoid wearing clothing that generates static electricity (wool, nylon, polyester, etc.).
• Do wear a static discharge wrist strap (refer to Tool Catalog) with the lead end connected to the
controller's ground terminal. These straps are available at most electronic equipment distributors.
Do
not wear these straps with power applied to the unit.
• Avoid contacting the electronic components on the circuit boards of the unit being serviced.
• Leave the circuit boards in their static proof packing materials until ready for installation.
• Return a defective controller for repair in the same static protective packing materials from which the
replacement component was removed.
• Check the wiring after servicing the unit for possible errors. Complete this task before restoring
power.