I'm not aware of anyone that tries to model a residential refrigerator using the refrigeration system, which is more commonly used for commercial buildings such as grocery stores with refrigerated cases. Rather, residential refrigerators are usually modeled as ElectricEquipment objects using the refrigerator's EnergyGuide label annual energy use.

Note: Other residential appliances (e.g., clothes washer/dryer, dishwasher, cooking range) are similarly modeled using ElectricEquipment and/or GasEquipment objects with inputs derived from EnergyGuide labels. However, unlike refrigerators, energy use for these appliances is very sensitive to how much the appliances are used/operated. Thus, there are various calculation procedures to go from the EnergyGuide label's operation assumptions to actual energy use based on the number of building occupants or number of bedrooms in the home.

OpenStudio's refrigeration systems are geared towards commercial refrigeration, so the would likely be way oversized for a residential refrigerator/freezer. You might be able to reduce the sizes of things, but the condenser inside, and beef up your refrigerator insulation values, but I recommend looking at the load calculation section in ASHRAE Fundamentals for guidance on typical operating values. A residential refrigerator cycles some, but is otherwise a fairly consistent load.