ACHRNEWS

Ice Breaker: The Hopscotch Method

February 4, 2008

Many system problems encountered by technicians are electrical in nature. Either the problem is an electrical defect, such as a defective switch or motor, or it can be traced electrically to the system problem itself, such as an open low-pressure switch as a result of a low system charge. In order to be proficient in troubleshooting a system problem, a technician must be able to efficiently troubleshoot the electrical components of a system.

An excellent method of troubleshooting an electrical circuit is to use a procedure referred to by some technicians as “hopscotching.” This method allows a technician to easily determine the electrical status of a control switch. Using a voltmeter, a technician can measure the electrical potential (voltage) at various points within a system and use this information to determine the electrical status of a control switch. To use this method, permanently attach one probe of the voltmeter to an electrically common point in a circuit.

In the example shown, L2 is an electrically common point for all of the components in this circuit. Attach the blue probe of the voltmeter to this point and leave it attached during the process. Now, move the red probe of the voltmeter around the circuit and determine which switch is electrically open or closed. If line voltage is read before a switch and after a switch, the switch is electrically closed. If line voltage is read before a switch and not after the switch, the switch is electrically open.

For example, let’s say the red probe of the voltmeter is initially connected before the CR contact to read line voltage, which is 115 V in this example. If the CR contact is electrically closed when the red probe is placed after the CR contact, the voltmeter should again read 115 volts.

If the voltmeter reads 0 V, the CR contact is electrically open. This process can be repeated for all of the switches in the circuit. Again if line voltage is read before a switch and after the switch, the switch is electrically closed. If line voltage is read before a switch and not after the switch, the switch is electrically open.

Another important aspect of being able to electrically troubleshoot a system is the ability to read and interpret wiring diagrams. Technicians need to be able to understand the electrical operation of a system’s components. Reading the system’s wiring diagram can do this.

There are several different types of wiring diagrams, the most useful of which is a ladder diagram. This diagram arranges the electrical components in an easy-to-read format so a technician can easily interpret the electrical sequence of operation of a system. Being able to read a wiring diagram in conjunction with being able to use the hopscotch method of troubleshooting should allow any technician to trace any electrical problems within a system.

Publication Date: 02/04/2008