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43 Cards in this Set
- Front
- Back
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What is the maximum allowable temperature penalty allowed in refrigeration lines? |
Suction 2F°, all other lines 1F° |
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What is the formula for temperature penalty? |
(2F° x total pressure drop) ÷ pressure equivalent to 2F° at design conditions |
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What is a double suction riser's purpose? |
To ensure proper oil return when a system with unloaders is running at maximum capacity |
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Why are discharge lines looped below compressors? |
To prevent liquid draining to head of compressors |
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A hot gas binding line is required when? |
The condenser can be at an ambient lower than the receiver to prevent receiver from becoming vapor locked |
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Copper tubing will expand? |
1 1/4" per 100 feet per 100F° change in temp |
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Rigid fixtures should not be connected directly to risers? True or false? |
True |
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What is the maximum allowable hanger distance between pipe as per the csa B-152? |
10 Feet |
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What is the pitch for the suction line? |
1/2" per 10 Feet in direction of flow (except ammonia) |
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Oil separators are used on systems with a sst below? |
-50 °F |
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What systems must have a oil separator? (3) |
Systems with a sst below -50°F All grocery store racks All ammonia systems |
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Hot gas line (3 pipe hot gas defrost) is sized? |
To handle calculate hot gas load (2x Evaporator load) |
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How do you size your receiver? |
90% full at 90°F |
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Copeland recommends a p-trap on a rise of ? And an additional trap every? |
3-4 feet and every 20 feet |
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Industry standard requires a trap be installed on a rise of ? And an additional trap every? |
5 feet and every 10 Feet |
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What is the best way to know where and how far to install a p-trap? |
Follow manufacturers recommendations |
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How do you get your actual pressure drop? |
(Pressure per 100 feet ÷ 100) x actual equivalent length of pipe |
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What is the formula for average velocity of a double suction riser? |
(Ssr flow rate × Ssr velocity) ÷ (dsrl flow rate + dsrs flow rate) |
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An increase in pipe size will do what to your velocity? |
Decrease velocity |
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A decrease in pipe size will do what to your pressure drop? |
Increase it |
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Minimum velocity in suction line? |
Horizontal - 750 ft/min Vertical - 1500ft/min |
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Maximum velocity in refrigerant lines? |
Liquid line - 300 ft/min Condensate - 150 ft/min Discharge line - 3000 ft/min |
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What does a undersized evaporator give you? |
Low SST Low mass flow Low capacity High TD Increase dehumidification(dry out product) |
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What is the ideal TD? |
10F° |
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What does an oversized evaporator give you? |
High SST High mass flow High capacity Low TD less than 8°F Decreased dehumidification(mold) |
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Due to the heat of compression condensers must be sized ? Compared to evaporators |
25% more |
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What is the formula for your transmission load? |
Q= U x A x Change in temp |
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What is the formula for infiltration load? |
Q= VOLUME x SERVICE FACTOR x AIR CHANGES x HEAT REMOVED |
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A lower K value will have better? |
Insulation |
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K value in metric is for material ? Thick |
One meter |
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What temperature kills most enzymes? |
170°F |
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Will lowering the temperature of a product kill enzymes? |
No it will just slow them |
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Below what temp will most bacteria become dormant and unable to reproduce ? |
39°F (4°C) |
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What temp must a cooler and freezer be at for food preservation? |
4°C (39°F) or less for cooler -18°C ( 0°F) or less for freezer |
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At what temp will ice cream keep solid? |
-10°F (-23°C) |
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Meat products should never exceed what temp? |
40°F |
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With a meat cooler what is a concern and how do you prevent it? |
Dehydration -keep low TD -use low velocity evaporator |
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What 3 foods will give off flavors to other foods? |
Fish Potatoes Onions |
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What do temperature fluctuations form on product? And which product is most susceptible to it? |
Ice crystals Ice cream |
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What is different about brazed plate heat exchangers? |
It subcools itself |
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C value = |
K value ÷ thickness |
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R value = |
Thickness ÷ k value |
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U value is equal to |
1 ÷ total r value |
