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Hvac > Meh > Flashcards

Meh Flashcards

1
Q

Types of valves and what they do and effects on fluids

A
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2
Q

Filter definitions

A
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3
Q

ASHRAE VS AHRI VS ABSA VS…

A

CSA & ABSA: B52-05
ASHRAE: flammability, toxicity,
Alberta Environment: administration of the Code of Practice
AHRI: determines refrigerant GWPs
National Office of Pollution 1996: Code of Practice

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4
Q

Number meaning in Refrigeration numbers 🦀

A
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5
Q

Entropy units

A

BTU/lb °R

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6
Q

Temp rise, temp difference

A

(∆T) Temp rise/drop -> SST/SDT & ambient
(TD) Temp difference (diff mediums) -> ambient & cond/evap

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7
Q

Def of work

A

Force * distance

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8
Q

HCFCs, HFCs, HFOs, etc

A

HFOs: (new), r1234y,
HFCs: r23, r32, r134a, r404a, r410a, etc
HCFCs: r22, r123, r124,
CFCs: r12, 13,

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9
Q

Spill vs rollout

A

Spill: interrupts the heating control circuit due to backdraft (hot flue gases spill out of the flue hood)
Rollout: Interrupts the heating cycle due to rollout (burner flame and flue gases remain the the burner compartment instead of heat exchanger)

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10
Q

Forward curved vs backwards vs axial curved noise

A

Forward: quiet
Backwards:
Axial: noisy

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11
Q

Flat blade

A

Medium air flow, low static pressure

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12
Q

Curved airfoil

A

High airflow, high static pressure

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13
Q

Radial tip

A

High air flow, medium static pressure

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14
Q

400CFM/ton for ACs and 450CFM/ton for heat pumps
1ton = 700sqft

A
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15
Q
A
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16
Q
A
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17
Q
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18
Q

PRV vs pressure relief vs pressure reducing, blowdown

A

PRV (pressure reducing valve) : limits the pressure for branch pressure use
Pressure relief valve: safety
Blowdown valve: Remove condensation from the receiver
Pressure controller: Starts and stops the motor to maintain receiver pressure

19
Q

Spring range

A

The range to produce total movement from one extreme position to another

20
Q

Pump down
Pump out

A

Pump down used on large built-up medium temp walk in coolers cuz of long lines
Pump out used on larger low temp to reduce short cycling

21
Q

Primary controller/control

A

Directly/indirectly controls the control agent

22
Q

Deviation
Offset

A

Deviation: length of time for control point and setpoint to equalize
or Difference between control point and setpoint at any instant
Offset: Sustained difference between control point and setpoint

23
Q

Line duty vs pilot duty

A

Line duty: interrupts the CURRENT directly to the motor
Pilot duty: interrupts a relay or something CURRENT that stops the motor

24
Q

Controlled device

A

Actuator/final control element/valve

25
Q

Controlled variable
Manipulated variable
Measured variable

A

Quantity or condition of the controlled medium
Quantity or condition of the control agent

26
Q

Range
Span

A

Difference between least and greatest values of a controller
Difference between two limits

27
Q

Sulphur, regulator places names, specific density/volume,

A
28
Q

Pipe controller output to actuator vs input sensor pressure

A

Output to actuator: 0-20psi
Input from sensor: 3-15psi

29
Q

remote bulbs are found in contact with _

A

controlled medium

30
Q

Usual NON ADJUSTABLE High limit setpoint

A

HL: 180F-220F

31
Q

Combination fan limit controller cut in and cut out temps

A

Cut out: 80-90F
Cut in: 120-140F

32
Q

Low ambient limit controller temperature

A

50F (same as changeover temp 50-60F)

33
Q

Furnace limit controls

A
34
Q

Usual ADJUSTABLE high limit

A

HL: 150-200F

35
Q

Burnt open vs shorted

A

Shorted: over current

36
Q

Resistance, inductance, capacitance, reactance, impedance opposes what

A

Impedance: total opposition to flow of current
Resistance: Limits amount of current
Inductance: opposes change in current
Capacitance: opposes change in voltage
Reactance:

37
Q

Fuses protect

A

Conductor

38
Q

Air permeability

A

Air escaping from building

39
Q

6-10 duct diameter

A
40
Q

30° TD

A
41
Q

Hydrometer

A
42
Q

Schedules/specification book, section|page number

A
43
Q

Vernier

A

Hvac (14 decks)

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