Tuesday, May 17, 2011

how to check out refrigeration compressor?

If your refrigerator sounds like it is turning on and off frequently or it just isn't cooling as well as it used to, there may be a problem with its compressor motor. In this tutorial, you'll learn the basics on how to test your refrigerator's compressor motor. But, before you get into testing the motor, I would recommend first ruling out the compressor relay.
Unplug the refrigerator or turn off the breaker that powers it. Since you will have to get to the backside of the refrigerator anyway, I would recommend you unplug it.

Modern Compressors have two operations that have to work together just to run. More items must be considered for them to work and work efficiently in systems. The 2 areas that must work together are electrical and mechanical. Either your compressor is broken inside or the motor and or start components are not working properly.

Ohm the compressor terminals to ground and across to each other.
1. If any read anything to ground the compressor is bad. If not go on to the next step.
2.Your readings between the compressor terminals should all be different and you should have 1 low 1 medium and 1 high resistance reading.
Add the low and mid reading together and the sum should be close to the highest reading. If it reads say 20% more or less then retest it a couple of times to confirm your not slipping on the terminals. If you get only 2 readings don?t panic wait 24 hours for the motor to cool off for sure and recheck it. If still no reading then your compressor motor is open. A new compressor or replacement of the appliance is required. If you now get the 3 readings described make a diagram you feel comfortable with as to where the wires go to each component before removing anything, then continue:
3 Assuming the above checks out: Get a new *Start relay *start capacitor if so equipped relay *external overload and *run capacitor if it has one. In other words everything that is external and attached to the wires or terminals on the compressor or wiring per your diagram and replace them on to the compressor. Then if it starts problem solved if it still does same thing the compressor is bad (broken mechanically inside the compressor) and you have to decide to replace compressor or replace the refrigerating compressor be it AC or Refrigeration.

*May or May NOT have this component:
*Start Relay:
MOST 99.999?% of refrigerators of the household type have a start relay of some kind and they vary in size shape and color. It plugs directly onto the compressor. SOME AC units but not all have one and it is different. These Resemble a box about 2?X2? X 3? with at least 3 terminals on it and these 3 terminals are marked 1, 2, & 5. Each of these will have at least 1 wire on them and there may be other terminals (4 & 6) as well that can be used with several wires on each.
* Start Capacitor
100% of AC and Commercial compressors that use a start relay (and remember some do not have one but those that do?) and only some domestic refrigerators use a Start Capacitor. At least 2 wires going to a black (usually) cylinder which is the start capacitor. Start Capacitors ALWAYS HAVE 2 or more Wires and ALWAYS HAVE TO HAVE A START RELAY.
*External Overload
MOST 99.9% of Household refrigerators, 80%+ of smaller commercial refrigerators, and most 90% of window unit AC?s but almost no central AC compressors Have an external overload. Those that do not have an internal overload. These vary in size and color and description a basic one is round 2 wires and generally black about quarter size USA AND IF USED ALWAYS MOUNTED ON THE COMPRESSOR with the other wires and terminals there.
*Run Capacitor
Some domestic refrigerators (can be a small rectangular box) medium and larger refrigeration and (99.999%... of all) AC central and Window units have a compressor that requires a run capacitor. These type units also have a fan motor that can require a run capacitor. These Capacitors always have at least 2 wires and often 3 or more if the capacitor also is wired to the fan motor.
If a compressor is tight due to linear expansion from heat a tip worth remembering is as something cools it contracts, except for water at freezing. A few times I have gotten a compressor to start after leaving it off for 6 to 12 hours then retrying it. See the compressor unless left off for 6 to 12 hours and sometimes as long as 24 hours may have expanded parts from heat. About 1/2 the time it is ok after new start components are installed with a start capacitor and relay. The other 1/2 the compressor will be ok for a day or 2 then stop again. A ?hard spot? in the movement of the internal parts in the compressor, and stopping on this hard spot it can?t overcome the ?tightness?.

If you follow most of these steps above you will arrive at a correct diagnosis well over 90% of the time ( allowing for what is unusual or for misunderstandings)

The working of compressor is as follows:----
The refrigerator compressor is the thing that compresses the refrigerant gas. It raises the unit’s pressure and temperature so that the the heat coils outside of the refrigerator can dissolve the heat of the pressurization. While cooling, the refrigerant becomes a liquid and flows through an expansion valve. As it’s doing this, the liquid refrigerant is able to move to a low-pressure zone from a high-pressure zone. Due to evaporation, it absorbs eat and this makes it cold. The coils within the refrigerator let the unit absorb heat which makes the inside of the refrigerator cold.

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