MP39 (R-401A) Reach In Cooler - Problem 1
The advanced troubleshooting section allows you to diagnose equipment problems by measuring all major operating parameters. High and low side refrigeration gauges display operating pressures. A digital temperature meter allows measurement of refrigerant and air temperatures in several key locations. PT charts are provided for the refrigerant being utilized. Electrical measurements can be taken at any of the test points on the electrical schematic. This is your opportunity to apply all of the theory and diagnostic techniques taught in this e-book and troubleshoot problems with realistically portrayed equipment faults. Above is a screen shot of the advanced troubleshooting user interface. The key features are indicated with circled red numbers. The features are explained in detail below in the following list.
Note that you can click on the circled numbers to go directly to the corresponding explanation. You can also click on any of the the circled numbers by the explanations to return to the screen shot.
The title informs you which equipment type and refrigerant you will be diagnosing. You must know whether the system is a high, medium or low temperature application so that you can come to conclusions about operating pressures and temperatures.
The B Button (B for Button) displays the column of symptom buttons below the circled 10. They all start off in neutral white. If you click one it will change to red with an upwards pointing arrow. This means that you've measured something that you think is higher than normal. If you click it a second time it changes to a downward arrow. This would mean that you've found a symptom that you think is lower than normal. Clicking a third time returns the button to neutral white. The more symptoms that you make record of, the easier it should be to determine the fault.
The T Button (T for Text Boxes) hides the column of symptom buttons below the circled 10 and displays a column of Text Input Boxes. They can be used to record your measurements so that you can refer to them later. You can toggle the B and T buttons and they will retain the information that you applied.
The Help Button opens this help page.
The Hint Button sometimes provides clues such as might be given by the equipment owner.
The PT Chart Button opens a new window containing the PT Chart relevant to the equipment being diagnosed. The troubleshooting boards default to Imperial units as do the PT Charts.
The Key button opens a list of keys or acronyms used on the piping layout, electrical schematic and on the symptom buttons. When the T button is clicked and the board is displaying the text input boxes, several keys are also displayed which when clicked open up an alert box with the acronyms definition.
When you believe that you have correctly diagnosed the problem click the Submit Diagnosis button to open a new window where you may submit your diagnosis and find out if you are correct.
The L, M and S buttons allow you to change the board to a Large, Medium or Small layout.
The button puts the board into Imperial Units mode. When clicked it turns green to indicate what mode is selected and the guages and PT chart will appear in Imperial Units. (PSIG and °F). The button puts the board into SI Units mode. When clicked it turns green to indicate what mode is selected and the guages and PT chart will appear in SI Units. (°C and kPa)
Click the button (Pressure 1) to view the suction pressure gauge reading taken at the P1 pressure test point. (The suction service valve) The button under the gauge and the P1 label on the piping layout both turn green to indicate that they are selected.
The high side guage is on the right. It becomes animated and displays the high side pressure when selected. Click the button (Pressure 2) to view the True Head Pressure. (High side pressure measured at the discharge service valve) Note that the label on the piping diagram has turned green to indicate where the pressure measurement is being taken.
Click the button (Pressure 3) to measure the Head Pressure at the King Valve. The label on the piping diagram will turn green when P3 is selected.
The unit nameplate provides electrical ratings for the equipment components.
The digital temperature meter has 9 buttons which correspond to the 9 temperature test points on the piping diagram. When you select a button on the key pad it changes to green and the corresponding test point on the piping diagram also changes to green providing a helpful visual reference. Note that you can change between °F and °C by clicking the button or button on the temperature meter.
the meter is in amps mode and you click a test point, the amperage draw
of all the loads in that electrical branch are displayed in the meter.
If there are "sub branches" those loads are
the meter is placed in the voltage mode one test point is automatically
selected. This is typically either the Common leg or Line 2. You must
select the 2nd test point. The volt meter
then displays the voltage potential between those 2 points. A volt
meter reports a voltage potential across an open circuit and across
power in an electrical circuit must be turned off before using an ohm
meter. If you fail to do so you may damage the ohm meter or at least
blow the meter's fuse. Anytime you put the meter
into ohms mode it is assumed that the power has been turned off. To
measure the resistance of a component select the 2 closest test points.
It is assumed that any parallel loads have been taken out of the
If you try measuring a circuit with several loads in parallel or series
you are likely to receive the following alert:
real life you will have an ohm reading representing the combination of
all the series and/or parallel resistances between the 2 test points you
selected. However those types of readings are
seldom useful when troubleshooting. That is why you must isolate
components from the rest of the circuitry to take a resistance
measurement. You may still attempt any measurement you wish and are not
restricted to adjacent
test points only. When it is somewhat obvious that a specific component
or wiring circuit is being tested you are likely to be given a reading.
The further apart your test points are, the greater is the liklihood
will receive the above alert instead of a meter reading.
When you take a reading that has direct continuity (zero resistance)
between 2 test points and there also happens to be a measureable
resistance in parallel, the measureable resistance load is ignored. This
is true in
real life as well as in these troubleshooting boards. That is because
electricity will favour taking the route of least resistance.
T5 is a temperature test point. It has turned green to indicate that it has been selected by clicking the T5 button on the digital temperature meter.
P2 is a pressure test point. (The discharge service valve) It has turned green because was clicked.
T6 is a temperature test point. (EEA or Entering Evaporator Air temperature) It will turn green when it is selected by the number 6 on the temperature meter key pad and the meter will display the temperature at that location.
T7 is a temperature test point. (LEA or Leaving Evaporator Air temperature) It will turn green when it is selected by the number 7 on the temperature meter key pad and the meter will display the temperature at that location.
T8 is a temperature test point. (ECA or Entering Condenser Air temperature) It will turn green when it is selected by the number 8 on the temperature meter key pad and the meter will display the temperature at that location.
T9 is a temperature test point. (LCA or Leaving Condenser Air temperature) It will turn green when it is selected by the number 9 on the temperature meter key pad and the meter will display the temperature at that location.
T3 is a temperature test point. It will turn green when it is selected by the number 3 on the temperature meter key pad and the meter will display the temperature at that location. This location can be used to measure the temperature of the refrigerant after exiting the condenser.
P3 is a pressure test point. (high side presure at the king valve) It will turn green when it is selected by clicking the button and the high side guage will display the pressure at that location.
The "A" button has been selected on the Amp meter. Test point 3 has been clicked on the electrical schematic and the meter is displaying the amperage draw at that location. In this case it is 0.9 Amps. That measurement can be compared to the FLA rating on the equipment nameplate. (circled 15)
The following chart keeps track of your progress through the 100 troubleshooting boards. You can click on the board numbers to return to the last board that you were working on.