What you will learn from Run Start Capacitors HVAC Motors | Electrical Basics :Common uses for capacitors in HVACThe two different types of capacitors used in HVACHow capacitors are madeRules for replacing a capacitorCapacitor safety measuresLots of valuable related links to give you a closer look so you will learn more about HVACRun Start Capacitors HVAC Motors | Electrical BasicsThere are two basic types of motor capacitors most commonly used in HVAC applications today. The run capacitor and the start capacitor. Motor capacitors are used to either increase run efficiency of the motor or to give it an initial start boost in torque to a motor. They are sometimes referred to as motor starter capacitors or power capacitors.Motor capacitors are only used for single-phase motors that generally see heavy use throughout the HVAC industry. mon applications for the start capacitor are generally limited to compressors and only to start the compressor. Typically, when a start capacitor is used, a special relay accompanies it in the circuit to disengage the start capacitor after the compressor motor gets its initial boost in torque from the start capacitor.

The most common relay for use in disengaging the start capacitor is the potential relay and the least common is the current relay. Power capacitors or motor start capacitor are also referenced when discussing HVAC capacitors.relocate ac unit costA motor capacitor can cause serious injury or worse so caution is advised whenever working around capacitors. window ac unit recycleMotor capacitors can be discharged using a resistor across its contacts. used ac condenser unitA 20,000-ohm resistor should be used to discharge the motor capacitor before working near or on a circuit with a capacitor in it. Remember, any motor capacitor, whether it be a motor start capacitor or a power capacitor can cause great injury or worse so handle with care.Related Link: HVAC Electric Motor Basics - A Closer Look Run Start Capacitors HVAC Motors - Inside CapacitorsThe inside part of capacitors are made up of an insulator between two metal plates.

The properties of this metal allow the capacitor to store electrons and the insulator prevents the electrons from flowing from one plate to another. The capacitor, therefore, stores energy in the form of electricity just as a battery would hold a charge of electricity. It is, therefore, necessary to take great care whenever working around capacitors even when the power to the unit has been turned off.Related Link: Troubleshooting HVAC Capacitors - A Closer LookRun Start Capacitors HVAC Motors - Capacitor SpecificsCapacitors are measured or rated according to a microfarad rating. Generally, run capacitors are rated for lower microfarad ratings from 3 microfarads to 50 microfarads. Start capacitors have much higher ranges and can be purchased in sizes all the way up to 800 microfarads. Capacitors also have a voltage rating on them with voltage ranging from 240 volts to 440 volts. It is good practice whenever replacing any electrical components to use an exact replacement. There are rules of thumbs that allow one to use a part that is not an exact replacement which is in a certain range but it is best to use an exact replacement.

To check to see if a capacitor is bad, use a capacitance tester to measure the microfarad rating on the capacitor. Compare it with the manufacturers rating. If it is more than ten percent off the microfarad rating on the capacitor replace it. With the Microfarad ratings, it is important to follow the 10 percent rule: that is stay within plus or minus 10 percent of the microfarad rating. With the voltage rating, it is okay to go up on the voltage with the replacement but never down. In other words of you have a capacitor rated for 370 volts that is 25 microfarads if you do not have an exact replacement but one that is 25 microfarads and 440 volts that is an acceptable replacement.Related Link: How does a Start Capacitor Help Start an Electric Motor - A Closer LookMotor Capacitors Available here for PurchaseRun Start Capacitors HVAC Motors - Motor Capacitors ConclusionAdditionally, if the motor or compressor fails to start for whatever reason part of the troubleshooting list of things to check will be the capacitor.

A bad capacitor can cause a motor to fail and burn up especially when heavy load conditions exist. It is difficult to tell unless you are familiar with capacitors but a capacitor that is bulged out on the top or sides is a bad capacitor. It needs to be replaced. There is always an inherent danger when working on electrical components and especially on capacitors. They will shock you even when the power to the equipment is off. Always have a trained expert HVAC technician check out the equipment. They can diagnose the problem quickly and efficiently and have the system back up in no time. They are also very familiar with all the dangers involved so it will done safely with no injuries.Related Links:Start Capacitors for HVAC Compressors - Motor Start AssistAir Conditioner Compressor Troubleshooting & RepairCondenser Fan Motor RepairAir Conditioning Blower Motor Repair The following Run & Start Capacitors for HVAC Motors video offers information for HVAC run capacitors that is helpful for someone wanting to understand the basics about capacitors.

One can probably skip the first third of the video. Other Run & Start Capacitors for HVAC Motors resources can be found here.Run Start Capacitors HVAC MotorsHow can you test the capacitor on your home air conditioner? To test the capacitor on a home air conditioning unit, shut off the power supply, discharge the unit and obtain the reading. If the reading is more than about six percent lower than the known rating, it is time to replace the capacitor. When using a digital multimeter to test a capacitor, the job is easier if it has a capacitance setting. After shutting off the power, short out the two terminals with a screwdriver. This ensures the unit does not send out an electric shock, and it is now safe to disconnect the wires from the unit. Place the leads of the meter onto the terminal to obtain the reading. If using an analog multimeter, set the meter to measure resistance before testing the capacitor. Turn off the power to the unit, discharge the capacitor and disconnect all of the wires connecting to it.