Can 231 be used outdoors?

The 231GRS34MD10 can be used outdoors with caution.   The pressure transducers are water resistant. If mounted with pressure port up (there will be a small offset due to gravity) water will run off. If mounted with pressure port down, water will collect at the seal between the metal and plastic of the housing. Water may seep into the transducer.      

If mounted with pressure port down, it is best to mount under some sort of shaded cover. This will protect from weather and thermal shock of the strong sun at sunrise. 

The -4°F relates to the LCD display. Below -4°F the LCD fails but the differential pressure portion of the device will work. Suggest purchasing the Model 231RS without a display. 

The Model 231MS series is NEMA 4 rated, designed to have pressure ports down. 

The Model 231RS series has a NEMA4 rated housing, however the remote transducer are weather resistant. Best when transducers are mounted under cover.