When replacing electrical components, it is very important to ensure the component is properly grounded. Do not overlook the importance of the ground wire. Although many times an ungrounded component will not affect the operation, it is not safe.
If a bare section of electrical wiring within a component, such as the winding of a motor, touches its casing, the ground wire will allow the current to flow safely to an earth ground. This will typically cause the overcurrent protection device (fuse or circuit breaker) to shut down the system. This prevents further damage to the system or anyone servicing it.
Sometimes, while replacing a fan motor, a technician might not reconnect the ground wire. There may be several reasons for this — it might not be possible or easy to connect the ground wire of the replacement motor to its original location (for example, the technician might need to extend the ground wire but for some reason does not), or the technician might not understand the importance of the ground wire. After all, the motor works, so why brother taking the time to ground it, right?
Depending on the type of mounting of the motor, this could be very dangerous. If the electrical wiring within the motor shorts to its casing without the ground wire connected, the case of the motor could be at the same electrical potential as the line voltage. If someone were to touch the case of the motor and a part of their body also touches the ground, current will flow through their body to the ground. This could lead to a serious injury or even death.
One electrical component that is occasionally overlooked as needing to be properly grounded is a metal-cased run capacitor. Sometimes, the run capacitor of a replacement motor is not able to be mounted in the same location as the original run capacitor, or the original fan motor did not use a run capacitor, so technicians need to configure a mount for the new run capacitor.
If a metal-jacketed capacitor is used, it should be mounted to a grounded frame of the cabinet. This will allow the current to flow to the ground if the plate within the capacitor touches its casing.
I have seen the run capacitor wire tied and/or taped to the leads of the motor and left dangling in the air. If the capacitor shorts and someone touches the capacitor casing and ground, current will flow through them to the ground.
I recently attended a Refrigeration Service Engineers Society (RSES) seminar where the speaker had pointed this out to the group, and, once again, the need for continuous education in our trade was reinforced for me. I have seen this mounting many times and had never realized the potential danger of it.
So, the next time you are replacing an electrical component and are having a difficult time connecting the ground wire, take a break, and figure out how to connect it. Do not leave the component ungrounded. It is unsafe for you and anyone else who works on the system.
Publication date: 3/5/2018