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Split Systems 4th year > Split Systems 4th year ILM 110405c > Flashcards

Split Systems 4th year ILM 110405c Flashcards

1
Q

What are four uses for the service valves on the condensing unit?

A

The service valves on the condensing unit are used for a variety of purposes, including:

  1. Charging and evacuating the refrigerant:
  2. Checking and adjusting the refrigerant charge:
  3. Performing diagnostic tests:
  4. Performing maintenance and repairs:

Overall, the service valves play an important role in ensuring that the refrigeration system is working properly and efficiently, and they are a crucial part of any maintenance or repair work done on the system.

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2
Q

The low side of the pressure gauge is what color?
______

A

Blue is low pressure.

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3
Q

The high side of the pressure gauges is what color?

A

Red is high pressure

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4
Q

Do the valves on the red or blue manifold gauge need to be opened to be able to read
the pressure in the system?

A

Yes, in order to read the pressure in a refrigeration or air conditioning system using a manifold gauge set, the valves on both the red and blue gauges need to be opened.

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5
Q

What is the yellow hose normally used for?

A

The yellow hose in a manifold gauge set is usually used for the refrigerant recovery process, evacuation and recharging procedures.

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6
Q

What is the sight glass used for on the manifold gauge set?

A

It allows you to see if there’s a liquid,gas bubbles or vapour in the system.

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7
Q

What should be done to the manifold gauge set if different refrigerants are used?

A

It’s important to properly clean and evacuate the manifold gauge set before using it to avoid the risk of cross-contamination,
which will help prevent mixing of refrigerants and avoid damage to the system.

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8
Q

The low side of the manifold gauge set is designed to read what pressures?

A

The low side gauge is a compound gauge designed to provide both pressure readings ( 0 to 250 psig) and vacuum readings (0 to 30’’ Hg).

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9
Q

What is one way to test the type of refrigerant in the system?

A

One way to test the type of refrigerant in the system is to use a refrigerant identifier. A refrigerant identifier is a device that analyzes the refrigerant composition and determines the type of refrigerant in the system.

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10
Q

Pressure gauges should never exceed 75% of their full scale range. Why?

A

Because doing so can lead to inaccuracies in the readings and damage to the gauge.

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11
Q

List the possible leak detectors.

A
  1. Electronic leak detectors:
  2. Bubble solution:
  3. Fluorescent dye:
  4. Halide torch:
  5. Infrared thermography:
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12
Q

Which leak detector uses an open flame?

A

The halide torch is the leak detector that uses an open flame.

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13
Q

Which refrigerant detector senses temperature changes around the possible leak by the
refrigerant?

A

The thermistor leak detector senses temperature changes that are caused when the refrigerant escapes from the system

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14
Q

Which refrigerant detector can detect a leak under pressure or a vacuum?

A

Electronic leak detectors can detect a refrigerant leak under pressure or a vacuum.

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15
Q

What color is the service cylinder for:
a. R-22:
b. R-410a:

A

a)R-22: is light green or grey b) R-410a: is pink

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16
Q

What is the purpose of a storage cylinder?

A

The purpose of a storage cylinder is to store and transport refrigerant in a safe and secure manner.

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17
Q

What are the three “R”s of refrigeration and what do they mean?*

A

The three “R”s of refrigeration are:
1. Reduce:
2. Recover:
3. Recycle :

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18
Q

Why is a vacuum pump used in an air conditioning system?

A
  1. To remove air and moisture:
  2. To test for leaks:
  3. To charge the system with refrigerant:
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19
Q

One tool used to determine that the deep vacuum (evacuation) in the closed system is
dehydrated enough is the:

A

is the vacuum gauge or vacuum meter.

A vacuum gauge or vacuum meter measures the level of vacuum or pressure in the air conditioning system.

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20
Q

What is the charging scale used for?

A

They are used to weight in the accurate charge in a refrigeration system.

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21
Q

What are the two purposes for the use of nitrogen?

A
  1. Pressure testing: Nitrogen is often used to pressurize the system after all the brazing is done to test for leaks.
  2. Brazing:
22
Q

Why is it important to purge with nitrogen before brazing?

A
  1. Prevents oxidation: When copper or other metals are heated during brazing, they are susceptible to oxidation. Oxidation can weaken the joint or cause leaks, which can lead to system inefficiencies, safety hazards, and equipment failures. By purging the system with nitrogen, it displaces the oxygen and prevents oxidation from occurring.
  2. Removes contaminants: Purging with nitrogen before brazing also removes contaminants such as water vapor, oil, or other debris that can be present in the system. These contaminants can affect the quality and integrity of the brazed joint, leading to potential leaks or other issues.
  3. Ensures an airtight system: Purging with nitrogen before brazing helps to ensure that the system is airtight. Leaks can occur if air or other gases are trapped in the system during brazing. Nitrogen purging helps to displace any air or other gases present in the system, ensuring that the brazed joint is strong and leak-free.
23
Q

Should there be pressure from the nitrogen inside the system?

A

In general, there should be pressure from the nitrogen inside the system when it is being purged or pressure-tested. However, the pressure should be controlled and monitored carefully to prevent over-pressurization or other hazards.

24
Q

What material is normally used for brazing?

A

The rod is normally used for brazing copper

25
Q

If there is a leak in a system that has already been running, what must be done to the
refrigerant before repairing the leak?

A

Do a Recovey procedure, The first step is to recover the refrigerant from the system using a certified recovery machine and refrigerant recovery tank.

26
Q

Can refrigerants be released into the atmosphere?
__________

A

yes

27
Q

Why is it important to remove the Schrader valve before any brazing on the service
valve?
___________

A

to speed up the recovery time.

28
Q

When should the gas ballast be opened on the vacuum pump?
________

A

when it is first started, which allows easier starting of the pump and quicker removal of the non-condensable gases.

29
Q

Why is it important to place the system under a deep evacuation? List two reasons.

A

It removes non- condesable gases.
It removes moisture

30
Q

What should the vacuum be brought down to for proper removal of non-condensable
and moisture?

A

For proper removal of non-condensable gases and moisture from a refrigeration system, the vacuum should be brought down to at least 500 microns (0.5 millibar or 0.0005 bar) and held for a period of time to allow the gases and moisture to be removed.

31
Q

If the system is deemed to be wet, what should be done?

A

A triple evacuation must be done.

32
Q

If the micron gauge rises slowly to 1500 microns and stays, what should be done?

A

This indicates moisture in the system and the process must be repeated

33
Q

If the micron gauge remains below 1500 microns during the 5-20 minute test, then what
can be done?

A

If the micron gauge remains below 1500 microns during the 5-20 minute test, it indicates that the evacuation process was successful and that the system is free of significant amounts of moisture and non-condensable gases. However, it’s important to keep in mind that this is just a preliminary test, and it doesn’t necessarily guarantee that the system is completely free of these contaminants.

34
Q

Before starting up a new unit the service valves position should be:

A

open and the refrigarent has been released.

35
Q

If an existing air conditioning unit needs to be started up, then how much refrigerant
should be in the system before the unit is able to be turned on?

A

at least 50%

36
Q

How long should the system run for before checking for proper charge?

A

minimum of 15 minutes

37
Q

What is the recommended CFM per ton of air flowing through the evaporator coil?

A

between 400 cfm to 425 cfm .

38
Q

What are the two common methods for checking for proper CFM?

A

Calculating by temperature rise and calculating by static pressure across the evaporator coil.

39
Q

What is the formula for CFM by temperature rise method?
______

A

CFM= furnace btuh output divided by
( 1.08xTemperature rise)

40
Q

Where are the temperature rise measurements taken from?
______

A

you must use an accurate thermometer to measure the supply air temperature and then the return air temperature.

41
Q

Of the two common methods for finding proper CFM of a system, which one is more
accurate?
_______

A

The static pressure method

42
Q

Using table 3, what is the pressure drop of a 3 ton coil with a CFM of 1200? (WB and
DB).
____

A
43
Q

When checking for refrigerant charge, how long should the system run before recording
any readings?
_____

A

let it run for at least 15 minutes

44
Q

List the possible ways of checking for proper charge?

A
  1. Temperature measurement:
  2. Pressure measurement:
  3. Superheat measurement:
  4. Subcooling measurement:
  5. Visual inspection:
45
Q

What readings are required for the superheat method?

A
  1. Evaporator coil temperature:
  2. Suction line temperature:
  3. Refrigerant pressure:

Superheat = Evaporator coil temperature - Suction line temperature - Saturation temperature

46
Q

Using table 5, determine the amount of superheat if the WB is 64 ̊F, the DB is 85 ̊F, and
an outdoor temperature of 85 ̊F.
____

A
47
Q

With the above answer, use table 6 to convert the pressure of the refrigerant to a
temperature. The pressure is 124psig and a suction line temperature of 55 ̊F. Is the
system charged properly according to the superheat?
__________

A
48
Q

What method of charging are you not supposed do, when a thermal expansion valve is
in use?*
___

A
49
Q

What recordings are used for the sub cooling method?
_____

A

the high pressure reading on the gauge
the temperature of the liquid as close to the evaporator as possible.

50
Q

Using tables 7-9, determine if the sub cooling of this system is properly charged. The
high pressure gauge for 410-A is 260 psig, the WB is 67 ̊F, DB is 90 ̊F, and the liquid line
temperature is 67 ̊F. Is it properly charged?
________________________________________________________________________
___

A

Split Systems 4th year (1 decks)

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