Ice Breaker: Tricks of the Trade
TRICKSBelow are some of the tricks that have been shared with me over the years.
• 5-2-1 Can She Run: While working with potential relays, an easy way to remember its wiring is “5-2-1, Can-She-Run.” Terminal 5 of the potential relay is connected to the compressor’s common terminal. Terminal 2 is connected to the compressor’s start terminal. Terminal 1 is connected to the compressor’s run terminal (in series with a start capacitor if used).
• C-S-R: On many single-phase hermetic compressors, the terminals can be identified by remembering the acronym “C-S-R.” While looking at the terminals and reading from left to right and top to bottom, the compressor terminals will typically be in that order: Common - Start - Run. Always test your findings with an ohmmeter to verify the terminals have been correctly identified. This normally works for single-phase hermetic compressors manufactured by U.S. companies.
• Heat Shrink Tubing: A temporary fix to damaged electrical insulation is to use heat shrink tubing. On electrical insulation that is cracked or worn, slip on a section of heat shrink tubing, then heat the tubing to shrink onto the insulation. This is only intended as a temporary fix as the wiring needs to be replaced as soon as possible.
• Thumb Point: When tightening and loosening nuts, bolts, screws or similar hardware, it is sometimes confusing to determine which direction to turn the bolt, nut, or screw. Here is a simple but effective method that works with all right-hand threaded nuts, bolts, screws or similar hardware: To determine which direction to turn the wrench, take your right hand and point your thumb in the direction in which the nut, bolt or screw is to move. Then observe the curvature of your fingers. This will be the direction to turn the wrench.
• Dime Size Disk: A possible temporary fix to a lost refrigerant charge in a removable power assembly of a TXV is to remove the power assembly and place a disk (about the size of a dime) between the diaphragm of the power assembly and the push rod of the TXV. When reassembling, the disk will push down on the push rods and open the valve. Be careful using this trick. The superheat valve of the refrigerant leaving the evaporator will be uncontrolled - it may be too high or too low depending on the thickness of the disk, but at least the valve will be open and some refrigerating will occur.
• Opened Jaws: To determine if the coil of a solenoid valve is energized, take the opened jaws of a clamp-on ammeter and place the open end next to the coil. If a current is measured, the coil is energized. Remember the jaws of the ammeter need to be open for this trick to work.
• Reverse Rotation: On a reciprocating compressor with a stuck rotor, a technician can attempt to free the rotor by reversing its rotation. On a three-phase compressor, switch any two of its electrical leads. This will cause the rotor to turn in the opposite direction which may free it. On a single-phase compressor, temporarily reverse the run and start leads and energize the compressor for one or two seconds. Do not leave the circuit energized for any longer as it may cause damage to the start winding. Then return the wiring to its normal connection and test the compressor. Sometimes this frees up the rotor.
These are only a few of the many tricks of the trade I have been fortunate to be given over the years. Next time you get together with other technicians, share your own tricks. If you have a trick you want to share with me, send them to email@example.com.
Publication date: 03/07/2011