When REMOVING OIL from a low pressure system, the temperature should be 130 degrees F because: LESS REFRIGERANT will be contained in the oil at the higher temperature . ... Liquid charged into a DEEP VACCUUM will boil and may lower temperatures enough to freeze water in the tubes.
What steps should be taken to prevent air accumulation into an idle low-pressure refrigeration system?
What steps may be taken to prevent air accumulation into an idle low-pressure refrigeration system? Leave the purge unit on-line at all times. Maintain system pressure slightly above atmospheric pressure. Open the air vents on the condenser.
Which of the following safety precautions should be adhered to for low pressure systems?
Which of the following safety precautions should be adhered to for low pressure systems? – Do not syphon refrigerant by mouth . -Avoid spilling refrigerant on the skin. -Use gloves and safety goggles when working with liquid refrigerant.
What should you do after reaching the required recovery vacuum on a low-pressure appliance?
- After reaching the required recovery vacuum on a low-pressure appliance wait a few minutes to see if the system pressure rises before charging.
- When leaks in the appliance make evacuation/recovery to the prescribed level unattainable, do not proceed with the recovery.
What is the typical design burst pressure for a rupture disk on a low-pressure centrifugal air conditioning system?
| Where should the discharge from a rupture disc be piped for venting? Outdoors | What is the typical design burst pressure for a rupture disk on a low-pressure centrifugal air-conditioning system? 15 psig |
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What precaution should be taken prior to recovering refrigerant from a chiller?
Question #4: What precaution should be taken prior to recovering refrigerant from a chiller suspected of having tube leaks? Drain the watersides of the evaporator and condenser . Run the circulating pumps. Be certain the purge unit is operating.
What should be on and what should be off during a vapor removal from a low pressure refrigeration system?
During vapor removal from a low pressure refrigeration system; the system water pumps, the recovery compressor, and the recovery condenser water should all be on.
What should be done to reduce refrigerant loss from a purge?
How would you SAFELY reduce refrigerant loss from a purge-unit on a low pressure unit? 1) Leak test and repair the chiller. 2) Seal the purge-unit discharge. 3) Plumb the purge-unit discharge back into the low side.
What steps should be taken before using a recovery unit to remove a charge?
Question #8: What steps should be taken before using a recovery unit to remove a charge? Acid testing the refrigerant . Purging the recovery unit with nitrogen. Changing the oil in the recovery unit.
What should be used to remove ice from sight glasses?
To remove ice from sight glasses or viewing glasses, use an alcohol spray .
Which of the following is an indicator of a leak in a high pressure system with a capillary tube?
Excessive superheat is an indicator of a leak in high-pressure systems having a capillary tube.
What is the most efficient method for leak checking a charged low pressure refrigeration unit?
The most efficient method of leak checking a charged low- pressure refrigeration unit is to pressurize the system by the use of controlled hot water or heater blankets . When controlled hot water or heater blankets are not feasible, use nitrogen to increase pressure. When pressurizing a system, do not exceed 10 psig.
Which component is particularly susceptible to leaks in low pressure refrigeration systems with Opendrive type compressors?
The shaft seal in open-drive compressor low pressure refrigeration systems is particularly susceptible to leaks.
How is refrigerant recovery?
In vapor recovery, the refrigerant is removed an HVAC system in a vapor state . Then the vapor is condensed into a liquid by the recovery unit and, finally, transferred to the recovery cylinder. The basic process is the same as liquid recovery to a certain point.
When using recovery equipment manufactured before November 15 1993 you must evacuate a low pressure chiller to what level before making a major repair?
For high- or very high-pressure appliances, the equipment must be evacuated to 0 psig before it is opened. For low-pressure appliances, the equipment must be pressurized to 0 psig before it is opened. Methods that require subsequent purging (e.g., nitrogen) cannot be used except with appliances containing R-113.
When can appliances containing refrigerants be recovered?
EPA regulations require that all comfort cooling appliances (air conditioners) containing more than 50 lbs. of refrigerant MUST be repaired when the annual leak rate exceeds 15% . EPA regulations require that all Commercial and Industrial Process Refrigeration containing more than 50 lbs.
How do you determine when enough vapor has entered the refrigeration system?
When the refrigerant saturation temperature increases above 32°F (freezing point of water) is the point when you know that the system has been charged with enough amount of vapor refrigerant.
Where is refrigerant added to a low pressure system during the charging process?
Where is refrigerant added to a low-pressure system during the charging process? The lowest access point on the system such as the evaporator charging valve .
Which of the following refrigerants should be used in a low pressure appliance?
Type 3 refrigerants are called low-pressure refrigerants as they are used in low-pressure appliances. Type 3 refrigerants include: R-11 (CFC) R-123 (HCFC)
What is the maximum safe pressure to impose on any low pressure system?
The maximum safe pressure to impose on any low pressure system is: 10 psig .
What method is recommended for raising the pressure of the refrigerant in a low pressure chiller?
What method is recommended for raising the pressure of the refrigerant in a low- pressure chiller? The EPA recommends circulating warm water through the chiller to raise the evaporator pressure .
Why do chillers require purge units?
Both CFC-11 and HCFC-123 chillers require purge units because : leaks in the appliance make evacuation to the prescribed level unattainable . ... Where does refrigerant go after it leaves the purge unit of a low pressure centrifugal system?
Which recovery equipment maintenance practices should be performed on a regular basis?
According to the EPA, which recovery equipment maintenance practice(s) should be performed on a regular basis? Check recovery device for refrigerant leaks .
What should be done before transferring refrigerant?
What should be done before transferring refrigerant to an empty cylinder? The cylinder should be evacuated .
What should a technician do if the refrigerant in a recovery cylinder is contaminated?
What should a technician do if the refrigerant in a recovery cylinder is suspected to be contaminated? Turn refrigerant in for reclamation.
Where is the lowest access point on a low-pressure centrifugal?
The lowest access point on a low pressure centrifugal air conditioning unit is the: The evaporator charging valve .
Which component is particularly susceptible to leaks in low-pressure?
| Where should the discharge from a rupture disc be piped for venting? Outdoors | Which component is particularly susceptible to leaks in low-pressure refrigeration systems with open-drive type compressors? Shaft seal |
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Where do leaks commonly occur in low-pressure systems?
On this side of the system, the refrigerant is a cold, low-pressure liquid. The refrigerant line on the system’s low side is often known as the suction line because the compressor’s action pulls refrigerant towards it. Leaks on the suction side most commonly occur in the evaporator coil or one of the fittings .
What precaution should be taken prior to recovering refrigerant from a chiller?
Question #4: What precaution should be taken prior to recovering refrigerant from a chiller suspected of having tube leaks? Drain the watersides of the evaporator and condenser . Run the circulating pumps. Be certain the purge unit is operating.
What should you do after reaching the required recovery vacuum on a low-pressure appliance?
- After reaching the required recovery vacuum on a low-pressure appliance wait a few minutes to see if the system pressure rises before charging.
- When leaks in the appliance make evacuation/recovery to the prescribed level unattainable, do not proceed with the recovery.
What is the best method to determine a chillers normal charge?
What is the best method to determine a chiller’s normal charge for leak rate calculations? Use the charge stated on the equipment nameplate . Approximately how much refrigerant vapor is left in an average 350-ton R-123 chiller at 0 psig once all the R-123 liquid has been removed?
What should systems that use r407c be leak checked with?
What should systems that use R-407C be leak checked with? Pressurized nitrogen and a trace amount of R-407C . You just studied 25 terms!
Which of the following components is located after the evaporator?
| Which of the following should be replaced if a system is opened for servicing? Filter drier | Which of the following components is located after the evaporator? Accumulator | What will non-condensables in a refrigeration system result in? Higher discharge pressure |
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What are the leak repair requirements for comfort cooling appliances and commercial appliances containing 50 lb or more of refrigerant?
Commercial refrigeration and industrial process refrigeration: Appliances containing 50 to 500 pounds of charge must be inspected once per calendar year until the owner/operator can demonstrate through leak rate calculations that the leak rate has not exceeded 20% (for commercial refrigeration) or 30% (for industrial ...
Which of the following is an indicator of a leak in a high pressure system with a capillary tube?
Excessive superheat is an indicator of a leak in high-pressure systems having a capillary tube.
When charging a low pressure chiller refrigerant should be introduced as vapor to raise the saturation temperature above?
When charging a low-pressure system, refrigerant should be introduced to the system as a vapor to raise the system’s saturation temperature to a minimum of; 36 degrees .
Which method of recovery relies on the internal pressure of the system?
Passive Recovery
System-dependent (passive) recovery is the recovery of refrigerant from a system employing the refrigeration system’s internal pressure and/or compressor to aid the recovery process. System-dependent equipment cannot be used with appliances containing more than 15 pounds of refrigerant.
What are the two refrigerant recovery methods?
The three different recovery methods are: vapor recovery; the push-pull method; and the liquid recovery method . In the vapor recovery method, the refrigerant is removed from the HVAC system in a vapor state. The vapor is then condensed into a liquid by the recovery unit and transferred to the recovery cyclinder.
