Not always. But if a compressor goes bad it can take out the contactor. I have replaced compressors before and found the contactor is still ok. In a commercial application Copeland will not honor the warranty if the contactor is not replaced at the same time a new compressor is installed. Not sure about residential but for a $15 contactor I would not gamble with it.
Common signs of a bad AC contactor include the air conditioner not turning on or off properly, frequent cycling, or a humming noise. To diagnose a bad contactor, visually inspect it for signs of burning or wear, and use a multimeter to test for continuity. If the contactor is faulty, it can be replaced by disconnecting power, removing the old contactor, installing a new one, and reconnecting the wires.
To determine if a 3-phase contactor is bad, you can check for physical signs of damage such as burnt contacts or melted components. Use a multimeter to test continuity across the contact terminals; if there is no continuity when the coil is energized, the contactor may be faulty. Additionally, listen for unusual noises when the contactor operates and check for overheating, which can indicate internal issues. If the contactor fails to engage or disengage properly, it is likely bad and should be replaced.
A contactor is tested by using a device called a Multimeter. By setting the multimeter to ohms and rx1 you can clip both prongs to the coil. If the multinmeter moves the contactor is good. If it doesnt move its bad.
low voltage from thermostat is not properly connected to contactor. transformer is bad. contactor is bad. >>>>>>>>>>>> You have an open pressure safety switch on the outdoor unit or the control wiring from indoors to outdoors is too small a gauge which will lower your control voltage at the contactor.
explain me about the contactor works with examples. if i want to control a motor with contactor. and how i can use contactor in loops with over load and circuit breakers.
metres
compressor contactor is bad. probably stuck in the closed position.
A definite purpose contactor is designed (and rated) for a specific load. So a lighting contactor is one example of a definite purpose contactor. A motor starter contactor is another example. So, a lighting contactor is a definite purpose contactor, but a definite purpose contactor is not necessarily a lighting contactor (it might be a motor starter, for instance).
No, you definitely cannot.
Replacing a 50 amp contactor with a 40 amp contactor is not advisable, as the 40 amp contactor may not be able to handle the load safely. This could lead to overheating, failure of the contactor, or potential damage to the connected equipment. It's essential to match the contactor's rating to the load requirements for safe and reliable operation. Always consult with a qualified electrician for such replacements.
To calculate the power of a contactor when you know the current (in this case, 30 amps), you can use the formula: Power (P) = Voltage (V) × Current (I). First, determine the voltage at which the contactor operates (e.g., 120V, 240V, or 480V). Then, multiply the voltage by the current: for example, at 240V, the power would be P = 240V × 30A = 7,200 watts (or 7.2 kW).