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C-4 Boilers, Steamfitting and Process Piping > Refrigeration > Flashcards

Refrigeration Flashcards

1
Q

Specific Heat Capacity

A

Is the amount of heat added or released to change the temperature of one pound of a substance by 1 degree F.

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2
Q

Superheat

A

Is the difference in temperature between a vapor and its condensation point

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3
Q

Calculate superheat temperature

A

Subtract its measured temperature from its condensation point temperature

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4
Q

Supercool

A

It measures the difference between a liquid and its boiling point

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5
Q

Ton to Btu/hr conversion

A

1 ton = 12,000 Btu/hr

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6
Q

Liquid Reciever

A

A storage tank for liquid refrigerant located on the high side between the condenser and the liquid line.

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7
Q

Liquid line

A

Tubing that carries liquid refrigerant from the condenser or liquid receiver to the metering device. (Smaller OD than suction line)

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8
Q

Metering Device

A

Located between the liquid line and the evaporator, its function is to lower the pressure of the refrigerant by restricting the passageway into the evaporator.

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9
Q

Accumulator

A

A tank in the suction line that prevents liquid refrigerant from flowing through the suction line and into the compressor.

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10
Q

Suction line

A

Tubing that carries refrigerant vapor from the evaporator to compressor. It should slope from the evaporator down to the compressor.

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11
Q

What is the nominal size for ACR tubing versus plumbing pipe?

A

Plumbing tube is equal to the OD minus 1/8”.

ACT tubing is designated by the actual OD.

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12
Q

Minimum radius for a 90 degree bend in copper tubing?

A

5 x Tubing OD

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13
Q

Why is the temperature that differentiates between solder and brazing?

A

If the temperature required to melt the filler alloy is:

  • below 840F it is soldering
  • above 840F it is brazing
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14
Q

Most flares on ACR tubing are made at an angle of _______

A

45 degrees

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15
Q

Capillary action

A

The movement of a liquid substance between two solid substances due to the molecular adhesive forces between the solids overcoming the liquid’s cohesive forces.

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16
Q

Fines are assessed up to _____ per day for failure to comply with the Clean Air Act.

A

$37,500 per day

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17
Q

Ozone Depletion Potential

A

The measurement of the ability of a refrigerant to destroy the ozone layer.

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18
Q

Global Warming Potential

A

Measure of the ability of a gas to contribute to global warming over time

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19
Q

A technician must be certified to what prior to performing refrigeration work?

A

Section 608 of the Clean Air Act

20
Q

Class A refrigerants are NOT known to be toxic at concentrations equal or below _____

A

400 ppm

21
Q

Class B refrigerants are those that ARE known to be toxic at concentrations equal to or below _____

A

400 ppm

22
Q

Flammability classification

A

1 : No flammability
2 or 2L: low flammability
3: high flammability

23
Q

Open motors are designed to operate at a given temperature rise as indicated on the motor nameplate. What does this mean?

A

It indicates the temperature rise over the surrounding air is operating at full-load conditions.

24
Q

A low pressure control and high pressure control is usually located on the:

A

Condensing unit

25
Q

The “term” nominal voltage refers to the:

A

Listed voltage

26
Q

What is the purpose of the holding circuit in a magnetic motor starter?

A

Holds the main contacts closed until the control circuit through the interlock is broken

27
Q

What is the density of untreated water?

A

8.33 pounds per gallon

28
Q

Convert psig to psia

A

Psig + 14.7 = psia

29
Q

What is effective voltage (Vrms)?

A

Vrms = Vmax x 0.707

30
Q

Inductance

A

An electrical property that opposes a change in current

31
Q

Power Factor

A

The relationship between a circuit’s true power and apparent power.

PF = (True Power (a wattmeter reading)/ Apparent Power ( calculated power in volt-amperes) x 100 = ___%

32
Q

Section 440.14!of the NEC requires that a disconnecting men’s be readily accessible and within sight of HVACR equipment. The disconnecting means a can not be more than __ away from the unit.

A

50 feet and cannot require ladder use, tools or moving obstacles out of the way.

33
Q

Out of the following control settings (set point, range, differential, cut-in) which is typically non-adjustable?

A

Range

34
Q

The run capacitor on a motor is used to:

A

Increase torque

35
Q

Fuses are sized by:

A

Both amperage and voltage

36
Q

1 HP = _____ watts

A

746

37
Q

When the temperature of a negative temperature coefficient material increases, it’s resistance will:

A

Decrease

38
Q

BTU to Kw conversion

A

KW = BTUhr/3412.142

39
Q

1 HP is equal to lifting _____ ft-lb per minute.

A

33,000

40
Q

The voltage to the motor should not be less than ____ % of the rated voltage.

A

90%

41
Q

1 ton of air = _____CFM

A

400

42
Q

A motor is a____ load.

A

Inductive:

An inductive load pulls a large amount of current when first energized, then settles down to a full-load running current after a few seconds or cycles. When switched, inductive loads can cause excessive voltages. Some examples of inductive loads include transformers, motors and wound control gear

43
Q

When replacing a motor what is the comparible current rule.

A

The replacement motor can never have a current draw less than the motor being replaced, but it may have a current draw that is 10% greater.

44
Q

What is the millivolt reading of a good thermocouple?

A

15 mv

45
Q

During replacement, if a different capacitance value must be used, a capacitance value up to___

A

10% greater that the original value can be used.

46
Q

How do you test if a capacitor is good?

A

Place an ohmmeter across both terminals. Set the range switch for the ohmeter to a high setting (x100). If the meter swings toward zero and then slowly returns to infinity, the capacitor is good.

C-4 Boilers, Steamfitting and Process Piping (3 decks)

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