A merchandiser system includes a case that has a door and a door heater. The system includes a low temperature refrigeration unit sized to fit within a case compartment and to operably couple to the case to maintain food product within a low temperature range. The system also includes a medium temperature refrigeration unit sized to fit within the compartment and operably couple to the case to maintain food product within a medium temperature range. The system includes a controller in communication with the door heater and is programmed to activate the door heater only in response to the low temperature modular refrigeration unit positioned within the compartment. One of the low temperature refrigeration unit and the medium temperature refrigeration unit is removably coupled to the case within the compartment, and is replaceable by the other refrigeration unit to change the temperature range of the product display area.