Troubleshooting Board Help

Packaged Conventional 2H2C - Board 20

Diagnose equipment problems with virtual test instruments. Electrical measurements can be taken at any of the test points on the electrical schematic. Test and improve your troubleshooting abilities with realistically portrayed equipment faults. The above screen shot indicates features with circled red numbers. Click the circled numbers to go directly to the corresponding explanation. You can also click on any of the circled numbers by the explanations to return to the screen shot.
The title informs you of the equipment type and the number of stages that the unit has. 2H2C stands for 2 heat 2 cool.
The The Help button opens this help page in a pop up window.
The Hint Button sometimes provides clues such as might be given by the equipment owner.
The Key Button opens a new window which provides the meaning of the acronyms used in the electrical schematic and the image buttons. Click this button for an example.
The Note button opens an alert message to remind you how clicking V on the volt meter toggles the initial test point location for measuring the various voltages and phases. Click this button for an example.
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 Test point 20 has been manually selected. Since the volt meter is measuring 24 VAC control voltage, it displays 24 VAC. (see note 9)
Each schematic has test points which can be selected for electrical readings.
The V button on the volt meter has been clicked multiple times so that it selects test point 7. This is the common test point for 24 VAC control voltage measurements.
Test points are available for measuring the capacitance of start and run caps. Sometimes the test points are not immediately adjacent to the capacitor but they are always available nearby.
The unit nameplate information provides electrical ratings for the equipment components.
The exterior view of the unit can be swapped to show interior views and individual components. (see 13)
These buttons change the images. In many cases the buttons are labeled with the keys used for the component. If you wished to see what the K13 relay looks like you could click the K13 button and the image will change to that relay. Here's a screen shot:
The Capacitance meter is very easy to use. If the MFD button is clicked it will turn green to indicate that capacitance mode is active. The test points surrounding any capacitor on the schematic may be clicked and the meter will display the capacitance of that component. The test points that you select will also turn green for a helpful visual reference. You can leave the capacitance meter active and continue selecting other pairs of test points which will then become the green or selected test points.
The Volt/Ohm/Amp meter can be used in any of it's three modes.

  Amperage Mode

If the Amp button is clicked it will turn green to indicate that the meter is in Amps mode. Any test point on the schematic may now be clicked and the meter will display the amperage draw at that point. The mode button and the currently selected test points turn to green. When 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 included.

  Ohms Mode

If the Ohms button is clicked it will turn green to indicate that the meter is in Ohms mode. Any two test points on the schematic may now be clicked and the meter will display the Ohms between those two points. If you select test points that are far apart you are likely to get an alert window stating that there are too many resistances to be meaningful. If you wish to know the resistance of a component select the two closest test points. The 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 circuit. If you try measuring a circuit with several loads in parallel or series you are likely to receive the following alert:
In 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 likelihood that you 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 measurable resistance in parallel, the measurable 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.

  Voltage Mode

If the Volt button is clicked it will turn green to indicate that the meter is in Volts mode. When the meter is placed in the voltage mode, one test point is automatically selected. This is typically L1 or L2. You may now select a second test point with the mouse cursor and the meter will display the voltage potential between those 2 points. A volt meter reports a voltage potential across an open circuit and across loads. If you wish to use a different default test point, click the volt button again and the next available test point will turn green. Remember that you can click the Note button while you are getting accustomed to the user interface.  

Here is an example. Let's assume that you wanted to measure the voltage output from the control voltage transformer. To do that you would need to click the V button four times until default test point 7 was selected and illuminated green. Then clicking test point 30 with the mouse would cause the volt meter to display 24 VAC if the transformer was working properly. This control circuit has a grounded common for the transformer. You could therefore obtain the same measurement by using test point 65 (ground) as the default test point.

  Progress Chart

The following chart keeps track of your progress through the 100 troubleshooting boards. Your browser highlights the numbers as visited links. You can click on the board numbers to return to the last board you were working on. The Help button on every board opens this page so that you can refer to the progress chart at any time. The green links are available for browsing.

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