Outdoor boxes may benefit from the option for additional material to rain proof the roof of the box – either a rain roof or a roof seam kit. Also, a drip rail may be installed above the entry door, and the exterior light switch weatherized.
Also, if refrigeration is included in the quote or project, addtional capacity should be calculated into the system to handle the higher outdoor temperatures. Outdoor temperature is rated at 110 degreesF for outdoor boxes verses 85 degreesF for indoor boxes. This results in a larger capacity (more horsepower) refrigeration system for the outdoor applications.
The condensing unit itself (outdoor unit) will also be increased in capacity relative to an indoor condensing unit to allow for the decrease in capacity with the outdoor temperature maximum of 110 degrees (in Texas), verses 85 degrees F indoors. For every 10 degreesF increase in the air cooling the condenser there is approximately a 6% loss in refrigerating capacity. Standard advertised refrigeration capacities by UL is at 90 degreesF, typically.
The condensing unit will also be fitted with winter controls to maintain the condenser pressure and temperature at a condition that will allow condensation of the refrigerant during cold weather. A weather cover (cabinet) will also be included in the outdoor rated refrigeration assembly.
This is a subject that is difficult for the layman to understand. It would seem that since a freezer box gets down to 0 degrees, that if one just turned the thermostat up to 35, presto – refrigerator. But there are a few problems with this.