The compressor suddenly trip off and it runs and after few minutes it trip off again
Compressor tipping is typically due to overheating. A single bimetal disc thermostat (e.g. Klixon brand device) in located within the motor windings within hermetically sealed compressors which will cut off motor current after the local windings have sufficiently overheated.
Unfortunately, by the time this limiter has activated, the compressor motor and pump has typically already suffered mild to major damage.
Compressor overheating is typically a result of low freon. The freon, besides cooling the compressor, also carries the lubricant, so low freon results in a hot compressor with poor lubrication, with some degree of permanent damage by the time the internal limiter has activated.
There are a few other possibilities, depending on system design, but some version of the above scenario is typical.
When the compressor runs hot, this also initiates chemical changes in the freon and oil resulting in acids with further attack both the compressor pump, motor windings and motor bearings, a viscous circle.
Compressor overheating can also be a result of contaminants circulating within the freon or evolving mechanical failure problems within the compressor pump or motor.
Better systems (very few high end residential central AC systems) include OEM or field installed high freon pressure and low freon pressure cut out switches connected to circuits which stop the compressor and keep it off when pressure are well beyond desired.
These are far more effective in protecting the compressor and preventing permanent damage.
Additional protection options are a compressor discharge temperature limit switch (shuts off the compressor if the outlet freon goes well above desirable outlet temps), and a flow switch which sense adequate condenser fan air flow and only allows the compressor to run when adequate air flow is present (a second or so after the condenser fan has started). (Since condenser air flow is what removes all the system and interior heat, the compressor should not run unless airflow is appropriate.)
While all the above 4 safety device strategies are relatively inexpensive, they are not present in the vast majority of residential AC systems sold in the US.
Jan 06, 2010 |
Carrier Air Conditioners