Why don’t you provide outdoor UPS systems in NEMA 4 or NEMA 4X cabinets?

The worst-case scenario for the VRLA (valve-regulated lead acid) batteries that are most commonly used in outdoor UPS units is when a battery charger’s regulator circuit fails and it is no longer able to regulate charging voltage. When that happens, oxygen and hydrogen gas production increases dramatically, which opens the safety valve and emits a substantial amount of oxygen and hydrogen. This scenario is also known as “battery out-gassing”. When a sealed NEMA 4 or NEMA 4X cabinet is used, the trapped mixture of oxygen and hydrogen can explode when a spark ignites the gases. This creates a highly dangerous situation with flying metal shrapnel that can cause severe personnel injury. Because of this, free-breathing NEMA 3R is the correct cabinet to use whenever VRLA batteries are housed inside an outdoor UPS cabinet.