Term
179. Which type of defrosting method condenses refrigerant gas into a liquid?
continuous defrost
air
hot gas
there is no defrosting method that does this |
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Definition
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Term
180. frost on cooling coil surfaces
comes from moisture in plant air
improves heat transfer
increases the k factor for the coil
only effects process freezing units |
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Definition
| Comes from moisture in the plant air. 10-1 |
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Term
181. Which of the following defrosting methods allows cooling during the defrost cycle?
hot gas
water
continuous
electric |
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Definition
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Term
!82. The air defrost sequence first closes the liquid solenoid valve to the coil, then ____ the fans
shuts down
cycles
slows down
continues to run |
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Definition
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Term
183. Electric resistance defrost
is commonly used on halocarbon systems
is the most energy efficient defrost method
works best in dx systems
is seldom used on halocarbon systems |
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Definition
| Is commonly used on halocarbon systems 10-5 |
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Term
184. Which defrost method does not involve a fan delay step in the defrost cycle?
electric
hot gas
water
air |
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Definition
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Term
185. In the continuous defrost method, the fluid that is used to keep frost from forming on the heat exhcange surface ______
is not blown from the evaporator because it is very thick and heavy.
must be replaced frequently as there is no way to prevent its dilution
must be heated to prevent it from freezing on the evaporators
is re-concentrated by an automatic re-generator |
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Definition
| Is re-concentrated by an automatic re-generator 10-8 |
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Term
186. The moisture/ air relationship is
the warmer the air, the more moisture it can hold.
the cooler the air, the more moisture it can hold
the more moisture the air has, the faster it will cool.
non existant |
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Definition
| The warmer the air, the more moisture it can hold 10-1 |
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Term
187. Frost build-up in storage freezers
is usually greater in the winter months.
is usually greater in the summer months
is not a problem on induced draft evaporators
is not a problem on forced draft evaporators |
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Definition
| Is usually greater in the summer months 10-2 |
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Term
188. which control component is usually used to stop liquid flow into an evaporator for temp management or to defrost the evaporator?
Expansion valve
float valve
gate valve
solenoid valve |
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Definition
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Term
189. Which type of defrost system is often used for a 38F dock unit?
Air
Water
Brine spray
electric |
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Definition
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Term
190. Frost build-up on the evap
increases capacity because the frost is a good insulator
decreases capacity because of reduced air flow
increases capacity because the frost is cold
increases capacity because the frost increases 'U' factor. |
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Definition
| Decreases capacity because of reduced air flow 10-3 |
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Term
191. Which one below is not a common method of defrost?
water
air
electric
deposition |
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Definition
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Term
192. Air defrost is frequently used
in plat freezers
in rooms operating above 38F
in rooms operating below 38F
in cold storage units |
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Definition
| In rooms operating above 38F 10-4 |
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Term
193. Which of the following is usually the final step in a hot gas defrost sequence?
Terminate gas delivery
Fan delay
Open suction stop valve
Pump Down |
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Definition
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Term
194. The hot gas defrost method
Delivers gas from the low side of the system to the evaporator coil.
is rarely used on industrial and commercial systems
delivers gas from the high side of the system to the evap coil
does not interrupt the refrigeration process |
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Definition
| Delivers gas from the high side of the system to the evap coil 10-9 |
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Term
195. The heat used to melt the frost and ice in hot gas defrost systems comes primarily from
cooling the gas to a lower temp
deposing the gas
condensing the gas
desuperheating the gas |
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Definition
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Term
196. Which of the following is not a source of frost?
Moisture from infiltrating air.
Moisture from inside sealed packages.
moisture from product
moisture from the respiration of freezer workers in the freezer. |
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Definition
| Moisture from inside sealed packages 10-1 2 |
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Term
197. If the air in the plant is relatively moisture free:
there is less need for defrosting.
the system will pick up more superheat in the suction lines
the total system cooling capacity will be reduced
there will be no impact on system operation. |
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Definition
| There is less need for defrosting 10-1, 2 |
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Term
198. As an evaporator builds up with ice:
there is no change in performance of the evap
heat exchange capacity of the evap goes down
heat exchange capacity of the evap goes up
the amount of flash gas created in the expansion device increases |
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Definition
| Heat exchange capacity of the evaporator goes down. 10-3 |
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Term
199. Manual defrosting of a sub-freezing evap is accomplished by
closing the suction valve
using blades and chip hammers
following the procedure developed and tested at the facility
closing the liquid supply valve to the evap and opening the hot gas supply valve |
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Definition
| Following the procedure developed and tested at the facility 10-15, 16 |
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Term
200. Which is not a cause of excess ice build up on evaps in low temp rooms?
blocked condensate drain lines
high discharge pressure
inadequate pump down time
time interval between scheduled defrosts is too long |
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Definition
| High discharge pressure 10-17 |
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