Control method of low temperature refrigeration of rooftop air conditioning unit

Abstract

The invention discloses a control method of low temperature refrigeration of a rooftop air conditioning unit. The method includes the steps that a first mechanical pressure switch with an off value P1 and an on value P2 is additionally arranged on an exhaust pipe; a second mechanical pressure switch with an off value P3 and an on value P4 is additionally arranged on an air returning pipe; the unit performs refrigeration operation, and two fans operate simultaneously when a exhaust pressure value is larger than or equal to P2; when the exhaust pressure value is equal to or smaller than P1, the first mechanical pressure switch is off, and a first fan stops the service; when an air returning pressure value is equal to or smaller than P3, the second mechanical pressure switch is off, and an indoor fan stops the service; when the air returning pressure value is equal to or larger than P4, the second mechanical pressure switch is on, an alternating current contactor of a second fan pulls in, and the second fan operates alone. According to the control method of the low temperature refrigeration of the rooftop air conditioning unit, refrigerants which are not evaporated completely can be prevented from entering and damaging a compressor during the low temperature refrigeration operation.

Description

Technical field: [0001] The invention relates to the field of air conditioning, in particular to a low-temperature refrigeration control method for a roof-mounted air-conditioning unit with a three-phase fan. Background technique: [0002] Due to the large cooling capacity required by the existing roof air conditioner, the indoor and outdoor fan motors generally use a three-phase motor to drive the fan, which is basically composed of a compressor, a condenser, an outdoor dual-axial fan, a throttling device, and an evaporator. And indoor centrifugal fan composition. During cooling operation, the air conditioner unit transfers heat from the indoor to the outdoor through the work of the compressor according to the refrigeration principle. When the refrigerating cycle of the roof air-conditioning unit in the prior art is in normal operation, the outdoor biaxial fan, the indoor centrifugal fan, and the compressor are all in normal operation. [0003] At present, in the actual u...

AI Technical Summary

Problems solved by technology

For example, places with large heat dissipation, such as computer rooms and forging workshops, require that the indoor and outdoor be separated, and the indoor ambient temperature should be kept at about 18-30°. When the indoor machines or equipment are running, they will continuously dissipate heat, resulting in indoor The temperature continues to rise, which affects the service life of the machine or affects the work efficiency of the workers. This requires the air conditioning unit to perform cooling operation even when the ambient temperature is low.

However, in the roof air conditioner of the prior art, in a low-temperature environment, the pressure of the high-temperature gas discharged from the compressor is low due to the low ambient temperature when the air-conditioning unit is running. The low evaporating pressure causes the evaporating temperature to be far lower than 0°, and when the evaporating temperature is lower than 0°, the condensed water on the evaporator will gradually turn into frost, thereby reducing the indoor air passing through the evaporator, causing the refrigerant to fail Enough heat exchange and complete evaporation into gas, carrying liquid into the compressor, causing the compressor to perform liquid compression will eventually cause the compressor to be damaged too quickly

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