While our customers are wholesalers, Packard knows that you, the contractor, have a choice. You are often presented with many buying options, and being well-informed about your purchase can help make your job easier and more successful.
This is why we have dedicated a section of our site for contractors. In this section, you will find helpful product tips, tools and some clips from our training classes. We’ve also provided a distributor locator so you can find the nearest wholesaler who can give you access to Packard products.
Start capacitor with a bleed resistor.
Have you heard this before? Why would this be the case?
In the HVAC/R industry, capacitors are frequently used. A capacitor stores and releases electrical energy. Many technicians can attest to the fact that capacitors release electrical energy because they have been shocked when they inadvertently got their finger across the terminals of a charged capacitor. A bleed resistor can be used to dissipate, or discharge, the stored electrical energy in a run or start capacitor.
The shock received from a charged capacitor is quite a concern. But another issue that may not be as familiar to technicians is damage that can occur to the system because a bleed resistor is not attached to the start capacitor. In fact, it is a major reason for compressor failure. The run capacitor is not exposed to this issue and does not require a permanently attached bleed resistor because it does not utilize a switch. But a switch is always used when a start capacitor is installed in an induction motor. This could be a centrifugal switch, as in the case of most pump motors. The centrifugal switch is typically mounted on the back end-bracket of the motor. In compressors, a centrifugal switch mounted inside the compressor would be exposed to the refrigerant and oil which could lead to switch failure. As a result, a relay is used and is mounted outside of the compressor.
The switch is normally closed. When the motor begins operating the rotor/shaft spins faster and faster. As the rotor/shaft reaches its operating speed the switch opens, removing the capacitor from the circuit. If the start capacitor does not have a bleed resistor attached, voltage can be stored in the capacitor. This voltage can be discharged across the contacts of the switch when it returns to its normally closed position. This can cause arcing across the contacts of the switch. Pitting, or even welding of the contacts could then occur. This can result in switch failure, or even catastrophic failure of the motor winding.
The next time you install a start capacitor, remember that a little device like the bleed resistor could determine the life of the motor.
Packard has developed a complete HVACR critical components training program, which has received approval by North American Training Excellence (NATE) - the leading certification program for HVACR technician, and the only test approved by the entire industry. Below are some video excerpts from our instructor led training courses which we hold at Wholesaler locations nationwide.
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