Maintaining Your ACE
Proper use of preventive maintenance procedures can ensure that the Cisco 4710 Application Control Engine (ACE) appliance operates properly and can minimize the need for time-consuming service procedures. This chapter contains maintenance procedures that you should perform regularly.
This chapter includes the following major sections:
•Maintaining Your Site Environment
•Using Power Protection Devices
Maintaining Your Site Environment
An exhaust fan in the power supply cools the power supply and the ACE by drawing in air through various openings and blowing it out through the back panel. However, the fan may also draw dust and other particles into the ACE, causing contaminant buildup, which increases the chassis internal temperature and interferes with the operation of various ACE components.
To avoid these conditions, we recommend keeping your work environment clean to reduce the amount of dust and dirt around the ACE, so that you can reduce the amount of contaminants drawn into it by the power supply fan.
This section contains the following topics about various environmental factors that can adversely affect ACE performance and longevity:
•Dust and Particles
•Electromagnetic and Radio Frequency Interference
•Power Source Interruptions
Temperature extremes can cause a variety of problems, including premature aging and failure of chips or mechanical failure of devices. Extreme temperature fluctuations can cause chips to become loose in their sockets and cause expansion and contraction of disk drive platters, resulting in read or write data errors.
To minimize the negative effects of temperature on ACE performance, follow these guidelines:
•Ensure that the ACE is operated in an environment no colder than 32°F (0°C) or hotter than 104°F (40°C).
•Ensure that the ACE has adequate ventilation. Do not place it within a closed-in wall unit or on top of cloth, which can act as insulation. Do not place it in direct sunlight. Do not place it next to a heat source of any kind, including heating vents during winter.
Adequate ventilation is particularly important at high altitudes. ACE performance may not be optimum when operating at high temperatures as well as high altitudes. You should do the following:
•Ensure that all slots and openings on the ACE remain unobstructed, especially the fan vent on the back of the ACE.
•Clean the ACE at regular intervals to avoid any buildup of dust and debris, which can cause it to overheat.
•If the ACE has been exposed to abnormally cold temperatures, allow a 2-hour warm-up period to bring it up to normal operating temperature before turning it on. Failure to do so may cause damage to internal components.
High-humidity conditions can cause moisture in the ACE. This moisture can cause corrosion of internal components and degradation of properties such as electrical resistance, thermal conductivity, physical strength, and size. Extreme moisture buildup inside the ACE can result in electrical shorts, which can cause serious damage.
Each ACE is rated to operate at 8 to 80 percent relative humidity, with a humidity gradation of 10 percent per hour. Buildings in which climate is controlled by air conditioning in the warmer months and by heat during the colder months usually maintain an acceptable level of humidity for the ACE. However, if a ACE is located in an unusually humid location, use a dehumidifier to maintain the humidity within an acceptable range.
Operating a ACE at high altitude (low pressure) reduces the efficiency of forced and convection cooling and can result in electrical problems related to arcing and corona effects. This condition can also cause sealed components with internal pressure, such as electrolytic capacitors, to fail or perform at reduced efficiency.
The ACE is for use at a maximum altitude of 6500 feet (2000 meters).
Dust and Particles
A clean operating environment can greatly negate the effects of dust and other particles, which act as insulators and interfere with the operation of mechanical components. Also, in addition to regular cleaning, follow these guidelines to deter contamination of the ACE equipment:
•Do not permit smoking anywhere near the ACE.
•Do not permit food or drink near the ACE.
•Use dust covers when the ACE is not in use.
•Close windows and outside doors to keep out airborne particles.
The oil from a person's fingers or prolonged exposure to high temperature or humidity can corrode the gold-plated edge connectors and pin connectors on various devices in the ACE. This corrosion on ACE connectors is a gradual process that can eventually lead to intermittent failures of electrical circuits.
To prevent corrosion, avoid touching contacts on boards and cards. Protecting the ACE from corrosive elements is especially important in moist and salty environments, which tend to promote corrosion. Also, as a further deterrent to corrosion, the ACE should not be used in extreme temperatures, as explained in the "Temperature" section.
Electrostatic discharge (ESD) results from the buildup of static electricity on the human body and certain other objects. Static electricity is often produced by simple movements such as walking across a carpet. ESD is a discharge of a static electrical charge that occurs when a person whose body contains such a charge touches a component in the ACE, especially chips, and causes the component to fail.
ESD is a problem particularly in dry environments where the relative humidity is below 50 percent.
To reduce the effects of ESD, observe the following guidelines:
•Wear a grounding wrist strap. If a grounding wrist strap is unavailable, touch an unpainted metal surface on the chassis periodically to neutralize any static charge.
•Keep components in their antistatic packaging until they are installed.
•Avoid wearing clothing made of wool or synthetic materials.
Electromagnetic and Radio Frequency Interference
Electromagnetic interference (EMI) and radio frequency interference (RFI) can adversely affect devices such as radio and television (TV) receivers operating near the ACE. Radio frequencies emanating from the ACE can also interfere with cordless and low-power telephones. Conversely, RFI from high-power telephones can cause spurious characters to appear on a monitor screen.
RFI is defined as any EMI with a frequency above 10 kHz. This type of interference can travel from the ACE to other devices through the power cable and power source or through the air like transmitted radio waves. The Federal Communications Commission (FCC) publishes specific regulations to limit the amount of EMI and RFI emitted by computing equipment. Each ACE meets these FCC regulations.
To reduce the possibility of EMI and RFI, follow these guidelines:
•Operate the ACE only with its cover installed.
•Ensure that the screws on all peripheral cable connectors are securely fastened to their corresponding connectors on the back of the ACE.
•Always use shielded cables with metal connector shells for attaching peripherals to the ACE.
Power Source Interruptions
The ACE is especially sensitive to variations in voltage supplied by the AC power source. Overvoltage, undervoltage, and transients (or spikes) can erase data from memory or even cause components to fail. To protect against these types of problems, always properly ground power cables. Use one or both of the following methods:
•Use one of the power protection devices described in the "Using Power Protection Devices" section.
•Place the ACE on a dedicated power circuit (rather than sharing a circuit with other heavy electrical equipment). In general, do not allow the ACE to share a circuit with any of the following equipment:
–Any other motorized equipment
In addition to these appliances, the greatest threats to the ACE power supply are surges or blackouts caused by electrical storms. Whenever possible, turn off the ACE and any peripherals and unplug them from their power sources during thunderstorms.
If a blackout occurs—even a temporary one—while the ACE is turned on, turn it off immediately and disconnect it from the electrical outlet. Leaving the ACE on may cause problems when the power is restored; all other appliances left on in the area can create large voltage spikes that can damage the ACE.
Using Power Protection Devices
A number of devices are available that protect against power problems such as power surges, transients, and power failures. The following subsections describe some of these devices.
Surge protectors are available in a variety of types and usually provide a level of protection commensurate with the cost of the device. Surge protectors prevent voltage spikes, such as those caused during an electrical storm, from entering a ACE through the electrical outlet. Surge protectors, however, do not offer protection against brownouts, which occur when the voltage drops more than 20 percent below the normal AC line voltage level.
Line conditioners go beyond the overvoltage protection of surge protectors. Line conditioners keep the ACE AC power source voltage at a fairly constant level and therefore can handle brownouts. Because of this added protection, line conditioners cost more than surge protectors—up to several hundred dollars. However, these devices cannot protect against a complete loss of power.
Uninterruptible Power Supplies
Uninterruptible power supply (UPS) systems offer the most complete protection against variations in power because they use battery power to keep the ACE running when the AC power is lost. The battery is charged by the AC power while it is available, so once AC power is lost, the battery can provide power to the ACE for a limited amount of time—from 15 minutes to an hour or so—depending on the UPS system.
Surge protectors should be used with all UPS systems, and the UPS system should be Underwriters Laboratories (UL) safety-approved.