Refrigeration and Air Conditioning Mechanic (RAC)

Third Period Package (19 Modules) Comments

Date: 5/26/2022 11:34:45 AM
Module: 140303d
Version:
Page:
Comment: The description at point #10 toward the end of it says; "The common or neutral line of the transformer remains connected and is not switched, as shown on the right-hand side of the secondary circuit at rungs 3,1 and 2." The problem here is the identification of Rung 3, 1, and 2 is inaccurate. The numbers on the right hand-side do not indicate the rungs themselves, they indicate where on the diagram we can find the change happening on this diagram when the loads are energized/de-energized. In this case, rung #6 load is the IDF, the IDF when energized will close the contact found on rung #3. Rung #7 has C has a load, comp contactor, when energized, this will cause a change in position at rung #1 C contact will close or open depending on C being energized or not. Similarly, rung #8 has CF, condenser fan relay has a load. When energized or de-energized, rung #2 will see the appropriate change of position. Again, when using a numbering system on wiring diagrams, the numbers found on the left are an indication of rung positioning within a wiring diagram, the numbers found on the right, indicate where we can find the change in contact positions within the diagram referring to the numbers on the left.
Status: Implemented


Archived Comments

Year: 2020

4/23/2020 11:19:59 AM
Module: 140301c
Version:
Page: 2
Comment: In the definitions under "Pressure Termination" it says; Pressure termination is accomplished by a pressure controller that senses the rise in evaporator pressure. The rise in suction pressure in the evaporator indicates the evaporator temperature has increased and the frost disappeared. It also provides redundant control of the defrost termination on the failure of temperature or pressure termination. This last line needs to be removed. "It also provides redundant control of the defrost termination on the failure of temperature or pressure termination." It is inaccurate and seems like a "copy and paste" from the proper definition of "Time Termination".
Status: Implemented

4/16/2020 10:27:53 AM
Module: 140301c
Version:
Page: 45273
Comment: On page 13, step 2 says the ORD forces gas from the top of the receiver through SV-A or SV-B. Problem 1, the outlet of the receiver going toward the ORD valve isn't at the top of the reciver, small detail but still important for visually understanding where the vapour is coming from. Secondly, SV-A and SV-B are not connected onto ORD from which the desbription claims the intermediate gas would come from, they are instead still connected to the discharge line where hot gas would come from, not intermediate gas. Sv-A and SV- B are in the wrong location and ORD ins't capable to accomplish it's described job.
Status: Declined

4/16/2020 10:18:51 AM
Module: 140301c
Version:
Page: 45210
Comment: This should be called "Three pipe hot gas defrost with conventional flow" Conventional flow means the direction the refrigerant flows within the evaporator is the same in cooling mode or defrost. The first paragraph is ok. The paragraph below figure 3 and the step-by-step description on page 11 contain mistake. Page 10; this type of system usually consists of 1 evaporator for 1 condensing unit. Which causes it to run out of heat quickly. Page 10 paragraph below figure 3 says; "Only one evaporator can be defrosted at any given time", which is true. Because it should be the only one. Page 11 step 3 says; "evaporator B continues to operate in refrigeration mode" If evap. B was to operate in cooling mode, evap. A would not run out of heat, now with the way this system is piped, evaporator B would not be able to see refrigerant flow since the higher pressure coming out of evap.a would block it. A single evaporator system would be simpler, and more accurate. Or simply say that the evaporator not in defrost is now on "Stand by".
Status: Implemented

4/16/2020 9:53:19 AM
Module: 140301c
Version:
Page: 8
Comment: Figure 2 drawing does not work. SV-A and SV-B are attached to the wrong evaporators. Also, this should be called "Two pipe Hot gas defrost reverse flow". Using a more complex diagram with a liquid line header, hot gas header and showing a "DDRV" Defrost Differential Regulating Valve and its operation would be more useful and more challenging to this level of students.
Status: Implemented