Final answer:
Altering the size of the suction line, specifically increasing it, can help promote oil return to the compressor in a refrigeration system without an oil separator.
Step-by-step explanation:
The question pertains to techniques for aiding in oil return to the compressor in a refrigeration system where an oil separator has not been installed. To assist in oil return without the use of an oil separator, options include altering the size of the suction line.
Increasing the suction line size can help in promoting oil return to the compressor. A larger suction line reduces the velocity of the refrigerant gas, allowing oil droplets more time to fall out of suspension and return to the compressor, which is crucial for its proper lubrication and operation.