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If the top sensor on a rack is showing a high temp alarm, what can you do?
Check blanking panel placement
Disable sensor and re-enable at a later time
Open floor tile to bring temp back in spec
Tell customer it will fix itself
If you receive an alarm on your cooling tower for a high water temp, what should you check first?
Check for bird strikes
Check to see if fan is running
Monitor chemical levels
None of the above
Dirty filters on a computer room air condition (CRAC) unit can cause excessive condensate to build up in the unit and cause a “water under floor” alarm.
What causes a low-pressure alarm in a CRAC unit?
The belts haven’t been adjusted properly
Blower motor failure
Loss of refrigerant
All of the above
What is the primary mechanical difference between CRACs and computer room air handlers (CRAHs)?
CRACs have refrigeration compressors as part of their primary system
CRAHs have refrigeration compressors as part of their primary system
CRACs cannot control humidity at supply like CRAHs can
CRAHs can not be isolated from the rest of the HVAC system for maintenance
Which of the following is NOT a benefit of ‘cold aisle containment’?
Increased efficiency of HVAC systems
Better control of peak temperature in the server racks
Work environment for technicians when compared to ‘hot aisle containment’
No need for ‘tile management’
What is the primary concern of having too low of humidity in your HVAC system?
Condensation collecting in the server racks
Static build up that can cause major electrical damage
Personal comfort is reduced
Fluctuating temperatures in the HVAC cycle
What are the benefits of proper ‘tile management’ in your data center? (Mark all that apply)
Tighter control of temperature regulation
Reducing the cost of cooling
Higher concentration of humidity under the floor
More even distribution of cooled air to the entire server rack
What is the biggest disadvantage to having too many perforated tiles in a datacenter
It overloads the CRAC units supporting the space
It reduces the overall underfloor pressure, while also reducing overall cooling impact
It starves CRAC units from return air which overloads fans
It is bad for the environment due to increased C02 from overworked compressors
Raised floor cooling can help provide directed cooling by placing perforated tiles only in areas where you would like to direct cooling. What is the standard volume of air that perforated tiles can provide.
150 to 250 CFM
300 to 400 CFM
450 to 550 CFM
500 to 600 CFM
Which of the following is NOT in the ‘refrigeration cycle’?
Which of these allow for cooling through a refrigeration cycle?
Heat of Compression
Heat Transfer dynamics
Low boiling point compounds
All of the above
What is “heat density” in terms of a data center’s HVAC system?
The average temperature of all sensors/racks
The lowest temperature and highest temperature in the environment added then divided by two
The temperature average in an area, but not the entire site.
Any noticeable temperature difference when moving through a Cold aisle
In Compound-X, which has a boiling point of 100°F, what is an example of it being in a super heated state?
Compound-X in a gaseous state with a temperature of 105°F
Compound-X in a liquid state with a temperature of 105°F
Compound-X in a gaseous state with a temperature of 100°F
Compound-X in a liquid state with a temperature of 95°F
What is the biggest advantage to direct exchange (DX) cooling systems
Easiest and most cost efficient to maintain
Accepts long piping distances
Air coolers can support multiple devices
Greater cooling capacity due to direct exchange
Why would it be more cost effective to have a cooler maximum temperature within your datacenter as opposed to using less compressor cooling?
It isn’t more cost effective, you are using compressors more which cost more energy
When too hot, Computer systems can ramp up their internal fans which can greatly impact the overall KW used within a datacenter.
Fan speeds on CRAC units will be lower at colder temperatures, reducing overall electrical load
Thermal efficiency of CRAC units is always better with lower temperatures.
What is a common cause for a drop in under floor pressures in a raised floor environment?
Fan speeds are not high enough
Hot isle causing low pressure in cooler areas
Poorly sealed wiring and cabling cutouts leading under floor within racks.
Too many perforated tiles for the given AC tonnage
Both C & D are correct
What is the lowest possible PUE in full EconoPhase operation?
Which statement below is not part of the basic refrigeration cycle?
Compressor takes a refrigerant vapor in from the low pressure side of the circuit, and discharges it at a much higher pressure into the high pressure side of the circuit.
When the refrigerant passes through the evaporator the refrigerant transfers its heat to the air and turns into a liquid.
When the hot refrigerant vapor discharged from the compressor travels through the condenser, the cool air or water flowing through the condenser coil absorbs enough heat from the vapor to cause it to condense.
The expansion valve is designed to maintain a specific rate of flow of refrigerant into the low side of the system.
What are the benefits of rack temperature monitoring?
Provide accurate indication of temperature going into the equipment
Provide a means to control cooling to the equipment
Provide alarm indication if temperature exceeds its set limit
Mission Critical’s 2019 July/August issue focuses on green data centers, intelligent power management, cooling options, and another installment of our State of the Mission Critical Industry roundtable article.