Unit 8 Flashcards by Thomas Rivera

T/F
After repairing a system that has had an electrical motor failure (compressor burnout) it is good field practice to reuse the recovered refrigerant in that system.

False

How well did you know this?

Not at all

Perfectly

T/F
Air entering a refrigerant system can eventually lead to compressor failure

True

How well did you know this?

Not at all

Perfectly

T/F
The maximum recommended pressure for leak testing is 150 psig on the low pressure side of the system

True
(Although it may be higher in certain instances. Check manufacturer’s data plate)

How well did you know this?

Not at all

Perfectly

T/F
While under a deep vacuum, any liquid water under the oil in the motor compressor assembly can be removed by operating the compressor motor for several seconds without any adverse effect on the system

False

How well did you know this?

Not at all

Perfectly

T/F
Clearance tolerances are such that the ordinary, clean refrigerant oil can be used satisfactory in a vacuum pump

False

How well did you know this?

Not at all

Perfectly

T/F
The oil in a vacuum pump should be changed after each time it is used

True
(This does not actually take place in the field. One should check the oil condition and pull microns)

How well did you know this?

Not at all

Perfectly

When using a “ standing pressure test” for leak detecting, _______________ should never be used since an explosive mixture can be created.

Pure oxygen

How well did you know this?

Not at all

Perfectly

Only two substances should be in the refrigeration system for proper operation. They are __________ and oil.

Refrigerant

How well did you know this?

Not at all

Perfectly

_____________ microns is equal to 1 mm Hg.

1000

How well did you know this?

Not at all

Perfectly

The electronic vacuum gauge is attached to the system so it can measure the pressure_____________ the system.

Within

How well did you know this?

Not at all

Perfectly

A deep vacuum involves reducing the pressure in a refrigeration system to a micron gauge reading of ___________ or below.

500

How well did you know this?

Not at all

Perfectly

Sludge is produced when moisture, acid, and _____________ our present in the system.

Oil

How well did you know this?

Not at all

Perfectly

A ______________ pressure could also mean refrigerant vapor is still seeping from the refrigeration system.

Increasing or rising

How well did you know this?

Not at all

Perfectly

Explain why, triple evacuations are not normally performed on large systems.

This takes too much time and is not cost-effective. Although in practice, triple evacuations may help to improve pull downs on large systems that are stubborn or have moisture in the lines.

How well did you know this?

Not at all

Perfectly

A pressure of 100 microns has been reached with the vacuum pump operating. The pump is turned off and the gauge rises to 5000 microns and stays there. What does this indicate?

There is still moisture in the system.

How well did you know this?

Not at all

Perfectly

A pressure of 100 microns has been reached with a vacuum pump operating. The pump is turned off and the gauge reading rises to 500 microns and stays there. What does this indicate?

The system is tight and passes the decay test after 10 minutes.

How well did you know this?

Not at all

Perfectly

Why is refrigerant not used for a system standing pressure test?

Refrigerant pressure will vary with temperature. This would also violate EPA regulations. This would be costly. If moisture is in the system, the refrigerant is now contaminated and cannot be reused.

How well did you know this?

Not at all

Perfectly

Why is nitrogen considered a “noncondensible gas”?

It cannot condense to a liquid as a refrigerant does. It does not compress and expand. This would cause high head pressures and inefficiency if left in the system.

How well did you know this?

Not at all

Perfectly

A pressure of 100 microns has been reached with the vacuum pump operating. The pump is turned off and the gauge reading rises above 5000 microns and keeps rising. What does this indicate?

There is a leak in the system.

How well did you know this?

Not at all

Perfectly

Why must all valves be opened when an evacuation is performed?

This allows the entire system to be pulled down and vacuum. If left closed, sections of the system may still contain moisture and noncondensibles.

How well did you know this?

Not at all

Perfectly

Why is it a good idea to remove Schrader stems from service valves prior to evacuation?

Schrader’s can restrict by up to 90%. Removing them decreases evacuation times and improves efficiency.

How well did you know this?

Not at all

Perfectly

Multiple choice
A micron gauge is used to measure _________

Absolute pressure is below 1mm HG.

How well did you know this?

Not at all

Perfectly

Multiple choice
To ensure accurate testing, the best material to use for connecting lines to the vacuum pump and gauge set is ___________

Copper tubing

Multiple choice
The best method of leak checking is when the refrigeration system is __________

Standing with dry nitrogen pressure of 150 psig in the system

Multiple voice A multiple evacuation means that____________

You pull a vacuum on a refrigeration system more than once, allow refrigerant, or nitrogen into the system between each procedure

Multiple choice When moisture is present in a refrigeration system, it will react with the refrigerant and the oil to form

Acid

Multiple choice Noncondensible gases ____________

Are undesirable in a refrigeration system

Multiple choice Which of the following represents the lowest vacuum?

1000 microns

Multiple choice A compound gauge ___________

All of the above

Multiple choice At what pressure range does the technician valve off the vacuum pump when evacuating to a deep vacuum?

500 to 300 microns

Multiple choice Moisture and a liquid state must be ___________ before it can be removed with a vacuum pump

Vaporized

Multiple choice To pull a vacuum means to _____________.

Lower the pressure in a refrigeration system below atmospheric

T/F Bishop says when performing a triple evacuation, the best place to locate the electric micron gauge is as far away from the vacuum part as possible

True

T/F When using a pressure gauge for standing leak test tapping the gauge with a 16 ounce hammer is a good way to make sure the needle is free.

False

What is the importance of installing a site glass in a system? And where should you locate it?

This allows you to see the flow and charge state of the liquid refrigerant. It indicates moisture.Not to be used in VRF systems. They are located on the liquid side before entering the metering device and after the filter dryer.

How can we use our senses when searching for a refrigerant leak on a refrigeration system or AC system, without the use of tools? Name all of them and explain.

Smell, see, touch and feel, listen. Look for oil spots or accumulation of dust and dirt. Oil leaks become darkened with dirt. Feel wet spots if it’s oily from refrigerant or just water condensation. Listen for escaping refrigerant. Sometimes you can smell the refrigerant leaking.

List tools we as techs use to search for leaks on an air-conditioning and refrigeration system. List all you can think of.

Electronically detectors of various types. UV dye. Soap bubbles. Nitrogen and trace gas. Also bring along blankets and tarps to isolate the unit if being used on a windy day.

Daniel and Camille are pulling vacuum on a Mitsubishi city multi system. I need to get down to 500 microns quickly, so they can go eat lunch before the lunch truck leaves. What are some ways they can increase the productivity of the dehydration and evacuation process? List all you can think of.

Remove Schrader. Use large diameter hoses. Triple evac. Turn on the crank case heater. Replace and change vacuum pump oil. Use multiple vacuum pumps at different sections of the system if there are taps.

T/F When noncondensibles and moisture are left in a system, hydrochloric and hydroscopic acids will form and deteriorate the motor windings, and cause copper plating

False (does not create hydroscopic)

List some ways to clean out contaminants from motor burnout on a semi hermetic compressor. List all you can think of.

Purge the system with nitrogen. Change the oil. Install HH filter drier. May need to change the drier multiple times. Put in acid neutralizer. Do acid test.

Christian response to a service call, the store manager complaint is the walk-in chill box is warm. The Board of Health was just there that morning and gave them a yellow card. They will return to recheck tomorrow if not repaired they will issue a red card. Shaun climbs on the roof and comes across a R 22 refrigeration unit and find a suction line filter dryer on the condensing unit. He notices the dryer frost up and then defrost. So he puts his manifold gauge on and finds he is running 58 psig suction before the dryer and 48 PSIG suction after the dryer, with a 190-160 PSIG liquid side gauge reading. Shawn then checks compressor amps and finds it is 3 A under the FLA. Suction line is dripping from condensation. Site glasses flashing box temp on the Dexter controller is 48°. What could be wrong with the system? What would you do to fix this problem? Explain in detail.

The filtered dryer is restricted and needs to be changed. This is starving the Evap causing poor temp and low amp readings. First pump down. Isolate the Evap and drier. Change the filter dryer and check the TXV strainer. Check condition of the oil. Pull vacuum. Break vacuum and allow refrigerant to circulate. Check new running conditions

How would you replace the oil in your modules, break it down and give me the steps.

Pump down the system. Valve off the compressor suction and discharge ports. Front seat accumulator. crack open the oil service port on the bottom with a catch below. Measure oil removed from the system and confirm against the manufacturer respect volume. Open the fill service port and insert the oil service straw inside. Replace oil by pumping in. Replace service caps. Pull vacuum and recirculate refrigerant.

Jonas and Mark are on a job at UH Manoa biochem lab and the mechanical inspector for the job site. Ask them a question while they are pulling vac on a VRF system during an install. they can’t get the microns down past 1000 mics. What should they do? When valves off the mics rise to 2000 then 3000 and keeps climbing after 10 minutes up to 3000 mics. Also the inspector on the job, ask them if they can just pass them and log it at 1000 mics since they got that low cause he like go home already? What should they do?

Tell him sorry they cannot do that. If he needs to go, they can pressurize the system and return the following day. Otherwise they must achieve the appropriate vacuum levels. There must be a leak in the system. Pressure test and find the leak. Isolate sections of the system to narrow down the leak location.

Larger hoses increase pumping capacity of a five CFM pump with a 3/8 inch hose by ___________ vs 1/4 inch hose?

4 times out of

What happens when air gets trapped in a refrigeration or AC system? Explain

This is a noncondensible which results in high head pressures, and poor readings. And the long run, this will also cause acid and damage to the system.

What can you do if you can’t find a leak on a split system in a business? Where are the condenser is on the roof and the evaporator is three floors below? Explain what you do.

Isolate the sections to find a leak if possible. If the leak cannot be found, inject UV die and return 24 hours to check for signs of leak with a UV light.

Lee Jay is dispatched to check for a leak on a condensing unit at the top of the mountain at Peacock Flats. What should he think of taking and how should he proceeded to find a leak if it’s windy out that day?

He should take two different types of electronic leak detectors if possible. Also soap bubbles. UV dye might be needed. He will also need sheets or tarp and rope to secure. This will help isolate the condenser for inspection with leak detectors when it’s windy.

Name the six different types of leaks

A) standing leaks B) pressure dependent leaks C) temperature dependent leaks D) vibration dependent leak E) cumulative; many micro leaks F) combination leaks

Leaks can flow under ….. A) B) C) D)

Paint, flux, rust, pipe insulation

We need to wash down, leaks after checking with soap or it will …. A) B) C)

A)Pit and corrode copper B) accumulate dirt and dust C) create a visual false positive. Throw off the next guy, mistaking it for a leak.

How many microns is in an inch?

25,400

How would you remove sludge from your system?

Change the oil. Install large suction line filter dryers. May need to change the oil multiple times. Install acid neutralizer.

If electroplating has happened in your system, what would you find if you were to open up your system? And what should you check?

There would be copper plating along the crankshaft bearings and potentially the valves and scrolls. Check for oil and compressor winding conditions (megometer). Can also check head pressure temp.

1 pound of water equals to a _________ in a system and will turn into ___________ ft3 a vapor if boiled to 70°

1pt 867 ft3

If you have a Sporland 305 – S – HH in your truck, what is this for? And what do the number and letters mean?

30 = capacity 5 = connection size 5/8 S = soldered HH= for acid burnout

What would happen if you start a hermetic compressor that is in a deep vacuum? What is the outcome?

You can cause terminal venting, resulting in catastrophic damage to the compressor. The oil and refrigerant insulate the internal windings. Starting it in deep vacuum will cause a short and damage the compressor.