Modularity has a variety of definitions across the industry. Some manufacturers equate modularity with multiple components--if a product has more than two parts, it must be modular. Tripp Lite's definition, however, is more firmly rooted in basic customer needs for continuous availability. Tripp Lite's Modular E3 Series, 3-Phase UPS Systems feature multiple 20 KVA power modules that help ensure continuous availability by providing failsafe redundancy (if one module is removed for maintenance, the others will support the load). Note: 20 kVA models do not provide redundancy since they only include a single 20 kVA power module. Modularity provides redundancy, not expansion capability. The UPS does not provide internal expansion capability (i.e.: it does not provide additional room for additional power modules). It does, however, provide external expansion capabilities. A user can connect two of the same UPS model in a parallel (1+1) configuration to double the UPS capacity. Up to four (4) 220/380 V Model UPS units can be paralleled for added system redundancy or capacity.