Oil return control method for fully constant frequency multi-connected air conditioning unit

Abstract

The invention discloses an oil return control method for a fully constant frequency multi-connected air conditioning unit. The method includes the steps that a, an outlet of an oil separator (1) is communicated with inlets of two constant frequency compressors (3) through a first oil return capillary pipe (2), the outlet of the oil separator (1) is communicated with an inlet of a gas-liquid separator (5) through an oil return pipe (4), an oil return opening (6) is formed in the bottom of the gas-liquid separator (5), the oil return opening (6) of the gas-liquid separator (5) is communicated with an inlet of a second oil return capillary pipe (8) with an electromagnetic valve (7), and an outlet of the second oil return capillary pipe (8) is communicated with the inlets of the two constant frequency compressors (3); b, when one constant frequency compressor (3) is started up to operate, the electromagnetic valve (7) on the second oil return capillary pipe (8) is closed, and when the two constant frequency compressors (3) are started up to operate at the same time, the electromagnetic valve (7) on the second oil return capillary pipe (8) is opened. By the adoption of the method, the oil mass of the compressors is balanced, and the excessively high exhaust gas temperature of the compressors can be prevented.

Description

technical field [0001] The invention relates to a multi-connected air conditioner unit, in particular to an oil return control method for a full fixed-frequency multi-connected unit. Background technique [0002] The multi-connected air conditioner unit in the prior art is referred to as a multi-connected unit for short, and it includes an outdoor unit, a plurality of indoor units connected in parallel, and two refrigerant circulation main pipes connecting each indoor unit and outdoor unit. The outdoor unit communicates with multiple indoor units connected in parallel through two refrigerant circulation main pipes. [0003] Each outdoor unit includes a compressor, an oil separator, a four-way reversing valve, an outdoor heat exchanger (a condenser for cooling and an evaporator for heating) and a gas-liquid separator. The outlet of the compressor is connected with the inlet of the oil separator, the outlet of the oil separator is connected with the first valve port of the fo...

AI Technical Summary

Problems solved by technology

Conventional compressors with variable frequency can run at reduced frequency to meet the pressure difference of the solenoid valve to ensure its normal opening and closing, but it is difficult to meet this condition in a system with all fixed frequency compressors. If a fixed-frequency compressor is used, it will cause huge fluctuations to the entire system, causing various failures and damages

It was also suggested that the electromagnetic valve should not be installed at all, but the inability to control the on-off of the oil return line will also cause a series of hidden dangers. For example, when only one fixed-frequency compressor is turned on in the system, the oil originally used to lubricate the two compressors will all be exhausted. If one compressor is supplied with too much oil and the other has too little oil, there is a risk of burnout in such a long-term lack of oil compressor, and the lubricating oil will drive the high-temperature and high-pressure refrigerant to flow back to the compressor. After all the lubricating oil supplied to the two compressors is supplied to one compressor, the return refrigerant originally borne by the two compressors will be fully loaded on one compressor, causing the discharge temperature of the compressor to be too high and triggering the shutdown protection

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