Oil return method for multi-split air conditioning in heating

An oil return method for a multi-split air conditioner in heating, wherein, the multi-split air conditioner comprises an outdoor unit, and an indoor system comprising multiple indoor units connected in parallel;

• the outdoor unit comprises a compressor, a four-way valve, an outdoor heat exchanger, an outdoor throttling element and an outdoor fan;
• each indoor unit of the indoor system comprises an indoor heat exchanger and an indoor throttling element;
• wherein, the oil return method comprises following steps:
• during heating operation, when oil return process is to be performed, without switching the four-way valve, adjusting an operation frequency f0 of the compressor to a first preset oil return frequency f1, and simultaneously, adjusting an open degree S0 of the indoor throttling element of each indoor unit of the indoor system to a preset oil return open degree;
• measuring operation parameters of the air conditioner;
• according to measured operation parameters and preset operation parameters of the air conditioner, judging whether the air conditioner operates abnormally or not;
• if the air conditioner operates abnormally, jumping to a step of exiting from the oil return process, here below, if the air conditioner operates normally, jumping to a step of measuring oil return time here below;
• exiting from the oil return process;
• after a period of time t1, adjusting the operation frequency f0 of the compressor to a second oil return frequency f2, and simultaneously, adjusting the open degree S0 of each indoor throttling element of the indoor system to the preset oil return open degree, wherein, f2<f1;
• measuring the operation parameters during the oil return process, and according to measured operation parameters of the air conditioner and the preset operation parameters of the air conditioner, judging whether the air conditioner operates abnormally or not;
• if the air conditioner operates abnormally, ending the oil return process;
• if the air conditioner operates normally, jumping to a step of measuring oil return time, here below;
• measuring oil return time;
• if the oil return time reaches a preset oil return time t2, ending the oil return process;
• and
• adjusting rotation speed of the outdoor fan, by measuring high pressure and low pressure of the air conditioner during the oil return process;
• such that if:
• (a) saturation temperature corresponding to the high pressure is greater than 50° C. and saturation temperature corresponding to the low pressure is greater than 12° C., reducing the rotation speed of the outdoor fan;
• and
• (b) the saturation temperature corresponding to the high pressure is less than 40° C. and the saturation temperature corresponding to the low pressure is less than 0° C., increasing the rotation speed of the outdoor fan.

An oil return method for a multi-split air conditioner in heating, wherein, the multi-split air conditioner comprises an outdoor unit, and an indoor system comprising multiple indoor units connected in parallel;

• the outdoor unit comprises a compressor, a four-way valve, an outdoor heat exchanger, an outdoor throttling element and an outdoor fan;
• each indoor unit of the indoor system comprises an indoor heat exchanger and an indoor throttling element;
• wherein, the oil return method comprises following steps:
• during heating operation, when oil return process is to be performed, without switching the four-way valve, adjusting an operation frequency f0 of the compressor to a first preset oil return frequency f1, and simultaneously, adjusting an open degree S0 of the indoor throttling element of each indoor unit of the indoor system to a preset oil return open degree;
• measuring operation parameters of the air conditioner;
• according to measured operation parameters and preset operation parameters of the air conditioner, judging whether the air conditioner operates abnormally or not;
• if the air conditioner operates abnormally, jumping to a step of exiting from the oil return process, here below, if the air conditioner operates normally, jumping to a step of measuring oil return time here below;
• exiting from the oil return process;
• after a period of time t1, adjusting the operation frequency f0 of the compressor to a second oil return frequency f2, and simultaneously, adjusting the open degree S0 of each indoor throttling element of the indoor system to the preset oil return open degree, wherein, f2<f1;
• measuring the operation parameters during the oil return process, and according to measured operation parameters of the air conditioner and the preset operation parameters of the air conditioner, judging whether the air conditioner operates abnormally or not;
• if the air conditioner operates abnormally, ending the oil return process;
• if the air conditioner operates normally, jumping to a step of measuring oil return time, here below;
• measuring oil return time;
• if the oil return time reaches a preset oil return time t2, ending the oil return process;
• and
• adjusting the open degree of the outdoor throttling element by calculating superheat degree of the outdoor unit such that if:
• (a) the superheat degree of the outdoor unit is greater than or equals to 2° C., reducing the open degree of the outdoor throttling element;
• (b) the superheat degree of the outdoor unit is greater than −1° C. and less than 2° C., maintaining the open degree of the outdoor throttling element;
• (c) the superheat degree of the outdoor unit is less than or equals to −1° C., increasing the open degree of the outdoor throttling element.