The overload relay is a protection device used in the compressor circuit. Power is applied to the compressor motor windings through the overload device, and the relay is used to add the start winding. The start capacitor provides increased starting voltage to the compressor windings, until the compressor is at running speed.
The sizing of both the start and run capacitors is critical to motor efficiency. There is a maximum of +10% tolerance in micro farad rating on replacement start capacitors. A capacitor that is too large can cause energy consumption to rise.
Starting up a compressor requires 4–8 times more electric current than running it. Over time, this jolt of power, which creates a surge of heat, can damage the compressor.
The name "Hard Start Kit" implies that it makes your system start harder. When in fact, it is designed to repair a system that is already hard starting. A hard start kit shortens the startup period of the compressor and reduces the amount of electricity it takes to start your AC. In fact, with a hard start kit, the electrical efficiency of the startup process is much higher than without one. This efficiency reduces heat and wear on the compressor and other important AC components. Most manufacturers of scroll compressor systems have hard starts already installed in them.
There are many opinions regarding a hard start. Some believe that the excessive power can damage the compressor motor by providing too much power. Others believe the excessive power actually causes movement in the motor. But there are some convincing test results that you can find that prove the 5-2-1 actually does a great job.
If your compressor is near the end of its life, then a hard start kit may prolong its life for a short time, but shouldn’t be viewed as a long term fix.
Signs that your compressor is hard starting:
- AC starts, then quickly shuts off after you turn it on: This is
called short-cycling, and it means there’s something wrong with your
- You hear clicking noises when the compressor starts: A clicking sound
points to a problem with your compressor, which is using too much
power to turn on (hard starting)
- Your compressor trips your circuit breaker: This means your air
conditioner is using too much energy to start, so your circuit
breaker trips before any serious electrical damage occurs. This is a
symptom of hard starting.
- Your lights flicker when you turn your AC on: This is normal to a
certain extent, but if you notice a dramatic flicker then it means
your AC is drawing too much power to start, which is a symptom of
The starting capacitor is the largest difference in the various 5-2-1
devices. You don't want too large of a starting capacitor. You need
to use the correct one for your application.
FYI: Multiply the load amps by 2,650. Divide this number by the supply voltage. The resulting number is the capacity of the capacitor you need in microfarads (µF). Add 10% of this number for the maximum microfarad