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Hvac > Unit 40 Typical Operating Conditions > Flashcards

Unit 40 Typical Operating Conditions Flashcards

1
Q

Standard eff evaporators operate at __° less than indoor ambient temperature. Standard indoor is 75°F - __°F = 40°F.

A

Standard eff evaporators operate at 35° less than indoor ambient temperature. Standard indoor is 75°F - 35°F = 40°F.

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2
Q

What are A/C systems design conditions rated?

A

95°F outside, 80°F inside, humidity 50%

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3
Q

What are A/C system design conditions while running?

A

95°F outside, 75°F inside, humidity 50%

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4
Q

T or F - The inside relative humidity adds a significant load to the evaporator coil and must be considered part of the load.

A

True

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5
Q

If the outside temperature increases, what happens to the head pressure and system capacity?

A

The head pressure will increase and the system will not have as much capacity.

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6
Q

What happens to system pressures when there is a change in heat?

A

When anything happens to increase the amount of heat that is absorbed into the system, the system pressures will rise.

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7
Q

What happens if the condenser cannot reject heat? Give some examples

A

If the condenser cannot reject heat, the system pressures will rise. Examples are the condenser fan is not working or if there are noncondensables in the condenser.

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8
Q

What happens if the outside becomes cooler than the inside, like at night?

A

The condenser may become too efficient and will hold back some of the refrigerant because the refrigerant is condensing in the first part of the condenser. Since there is more refrigerant in the condenser tubes, the evaporator will become starved and the system loses its cooling capacity.

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9
Q

What can happen to the evaporator if it becomes starved?

A

It can operate at below freezing temperature and may ice up solid.

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10
Q

What can be done to prevent condensers from getting too efficient?

A

Use a variable speed condenser fan. The fan will run at high speed during hot times and low speed during milder temperatures.

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11
Q

Standard eff evaporators operate at __° less than indoor ambient temperature. Standard indoor is 75°F - __°F = 40°F.

A

Standard eff evaporators operate at 35° less than indoor ambient temperature. Standard indoor is 75°F - 35°F = 40°F.

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12
Q

Standard eff condensers operate at __° more than outdoor ambient temperature. 95°F + __°F = 125°

A

Standard eff condensers operate at 30° more than outdoor ambient temperature. 95°F + 30°F = 125°

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13
Q

High eff evaporators operate at__°F less than indoor ambient temperature. 75°F - __°F = 45°F

A

High eff evaporators operate at 30°F less than indoor ambient temperature. 75°F - 30°F = 45°F

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14
Q

Standard eff condensers operate at __° more than outdoor ambient temperature. 95°F + __°F = 125°

A

Standard eff condensers operate at 30° more than outdoor ambient temperature. 95°F + 30°F = 125°

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15
Q

High eff evaporators operate at __°F less than indoor ambient temperature. 75°F -__°F = 45°F

A

High eff evaporators operate at 30°F less than indoor ambient temperature. 75°F - 30°F = 45°F

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16
Q

High eff condensers operate at __°F more than outdoor ambient temperature. 95°F + __°F = 115°F.

A

High eff condensers operate at 20°F more than outdoor ambient temperature. 95°F + 20°F = 115°F.

17
Q

Why does a high efficiency condenser operate at much lower head pressures?

A

The high efficiency condenser has a larger surface area and uses modern alloy surfaces and fins. This allows the condenser to reject heat much more rapidly. This brings temperature down and reduces the head pressure.

18
Q

What type of metering device do you find on a high efficiency system?

A

High eff systems use a TXV rather than a fixed bore device.

19
Q

How do you determine EER?

A

It is the amount of output in BTUH divided by the number of input in Watts. 36000 Btuh / 4000 W = EER of 9

20
Q

What is SEER?

A

Seasonal energy efficiency ratio

It is an efficiency rating system that takes includes the startup and shutdown cycles.

21
Q

What is the minimum SEER?

A

13

22
Q

What device is used to measure voltage and resistance?

A

Voltimeter

23
Q

Absorbs heat, which is related to it’s operating pressures and temperatures.

A

The Evaporator

24
Q

Rejects heat and has a predictable relationship to the evaporator load and outdoor ambient temperature.

A

The condenser

25
Q

What does eer stand for

A

Equipment efficiency rating

26
Q

AHIR means

A

American heating refrigerant institue

Hvac (29 decks)

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